AudioCircle
Other Stuff => Archived Manufacturer Circles => Ellis Audio => Topic started by: David Ellis on 6 Mar 2005, 03:31 am
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The pupose of this string is to address the modifications I performed for the Jolida 302b. I believe the componets I upgraded were the most critical parts under the hood of the 302b. Please query me in this forum with any questions you may have regarding these modifications.
Also, if anyone has significant fear about soldering under the hood of their Jolida amplifier, I highly recommend Bill's work at Response Audio. He has much more experience with these amplifiers than me, and has gone deeper into the amplifier. I suspect that Bills mods should & will sound a scosh better because his mods are more pervasive.
http://www.responseaudio.com/
My mods
http://www.ellisaudio.com/jolidamods.pdf
The Schematic
http://www.ellisaudio.com/302b.pdf
As a side-note, I think there is something very interesting happening with the Jolida 302b. It seems to be todays version of the Dynaco ST-70. The sound quality is extremely good, and the ability to putter with the 302b is very good. I agree the Jolida 302b is a very good amplifier worthy of time & listening.
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Dear Dave,
what a good idea!
Many thanks for the documents and the explanations.
regards,
Pierre-Etienne
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Dear Dave,
I have absolutely no doubt about the result (even if you say yourself that you are not an "amplifier guy"). I am just a bit impressed and curious to know you selected the components you had to upgrade?
There is a very interesting discussion in the Response Audio circle (http://www.audiocircle.com/index.php?topic=11263&postdays=0&postorder=asc&start=10) about modifications.
kind regards,
Pierre-Etienne
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They are direct signal path items and power supply tweaks.
All of the signal goes right directly through the coupling capacitors, and resistors.
The power supply diodes and bypass capacitors reduce power supply ripple. The diodes are very fast and have a nice soft recovery. The bypass capacitors should better filter any ripple after the rectification. Elecrolytics have a very high ESR. I actually performed the bypass capacitor upgrade in isolation. I was very skeptical about this before this part of the upgrade. I wasn't skeptical afterward.
These elements are very basic to any guy that can read a schematic.
Dave
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Hi,
This is good stuff! I've just done similar mods this week, except I also replaced all the signal path resistors with Dale Vishays, removed the balance circuit, added new interconnect wire, rca jacks, a logarithmic TKD volume pot & ELMA switch, and converted to PP Triode mode (which I like a lot). Since I removed the balance knob, I sanded a piece of cherry trim, oiled it up, and added some heavy gold-plated knobs to finish it up! I ended up removing the xformer cover -- it had a broken internal support and kept vibrating (60hz) due to the magnetic field in the power xformer...
Interestingly, my 302B schematic (and my unit) have several different resistor sizes from yours. The generic SJ-502/302 schematic, http://www.drtube.com/schematics/jolida/sj-502a.gif, has at least the following differences: R13&R16 are 1K vs 10K; Trim Pots are 30K vs 22k; R14&15 are 12K vs 20K. There may be other diffs as well. First I've heard of that!
Anyway, my 2001 302b is of this seemingly older design. It might be worth mentioning in your writeup...
From my mod experience, the most shocking difference was the addition of the HEXFRED rectifiers (I used 1200v/6A IR's). They seemed to dramatically tighten up the bass and lower mids -- I'm not entirely sure why! I haven't changed or added to any of the PSU caps yet.
The Auricap coupling and ground caps made the next biggest improvement, followed by the TKD pot. Finally, the signal path resistors seemed to quiet the amp even more, and seemed to smooth the upper mids and treble. When finished, I was amazed by the overall change. A dramatically better amp -- all for ~$300 or so.
I did the Triode mod last. While you lose half of your power (only 3dB at the ears...), I found the amp lost a little of its raw edge, but sounded much more engaging, smooth and warm on acoustic vocal music & instrumentals. It may be a little less tight overall on heavier rock, but I think I'll keep it this way since I like the overall change.
Just my $0.02!
Rich
(http://www.sheltons.net/temp/JolidaMods.jpg)
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Interestingly, my 302B schematic (and my unit) have several different resistor sizes from yours.
This appears to be a 302A/502A schematic. I didn't realize the schematics could be so similar. Mine is a 302B schematic. This would probably explain matters. At first it appeared there were errors in the schematics, but at second glance these are likely some of the differences between the "A" and "B" series Jolida amplifiers.
I didn't implement the diodes in isolation in the amplifier, but did accomplish this in my CD player. The diodes to have an impact, but I think this impact is lesser than coupling capacitors.
About 2 years ago I tried Auricaps behind my tweeters. I liked, them. They had a very smooth/lush midrange, but lost some detail compared to the Sonicap. I can easily understand how folks really like the Auricap and why it has become so popular. All-in-all, I thought the quality of the Auricap was on par with the Sonicap. I perfer the detail of the Sonicap, but this is my opinion.
Do you have empty holes for bypass capacitors on you power supply board?? My 302b had these, but I don't know if you amp has them. As mentioned, I accomplished this in isolation and it worked very well.
Indeed your work is more pervasive than mine. You are very welcome to post your iteration of mods with pictures in this forum. I am a bit curious about removing the balance control knob. This makes very good sense, but I didn't putter with anything serious, but this mod is free.
Dave
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I agree the schematic is an older 302a/502a version, but up until now, I've understood the difference between the A and B models was the cosmetic faceplate. Mine is an early B model, but matches the earlier A schematic. I would guess they evolved the design a little over time.
I have the holes for the three extra capacitors, and I think that's a great idea to add the bypass caps there. Pretty easy mod, and I can see where you got a nice result from that.
I actually took a number of pictures while I was doing the mods (great insurance when you screw something up:) ). I'll try to sit down and document some of the things I did.
My input circuit has two tiny, cheap pots (and questionable hookup wire) between the RCAs and the L&R input solder joints on the PCB board. I decided to remove both the vol pot and bal pot/board, then replaced the RCAs, input wire and added a single, high quality 100k volume pot (tapered) whos output is connected to the PCB input at the same location as before. The TKD is expensive at $58, but sounds great (and fits well in the tight space). The Alps Blue Velvet is another recommended pot, and is much cheaper. The Alps Black, and several others, are too large to fit. I figured this out from some AA posts. I also replaced the input wire with some 21.5 gauge Cardas silver shielded cable. That was probably overkill, and was tough to work with. Some nice unshielded hookup wire would probably be fine.
I've also heard that some of the 302s & 502s have better volume pots than others -- mine was definitely junk, and very scratchy/noisy!
One warning -- at first I just removed the balance circuit and used the old Vol pot. You lose a fair bit of resistance in the input path (50K I think), so the vol pot got very touchy. It also sounded terrible, and tended to distort at what I thought was a fairly low volume. I couldn't figure out why it sounded worse than it did with the balance resistor in the circuit. Anyway, I forged ahead and bought the 100k TKD. After installing it, all was well again, and the sound was clean and smooth throughout the input range. I also replaced the selector switch at the same time since Bill at Response felt that was a weak point in the circuit. Very strange...
I think I'll try your bypass cap mod next... I'll let you know how it goes!
Here's a shot of the resistor mods, the ELMA selector switch, and the TKD pot:
(http://www.sheltons.net/temp/ResistorMods.jpg)http://
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Hi Dave,
One question... I was looking at my power supply PCB photos and I see places for C1x (x not legible - located near end of PSU board) and C12 (near center of board) which correspond to the two .47 uf sonicaps you have on the top of the psu board [EDIT: see yellow arrows on added photos below]. C12 goes from +B to ground. C1x appears to go from +B2 to ground. Here's the problem. I don't see a spot on either side for the third cap, which I infer goes from +B1 to ground. Is that right, and if so, where did you attach it? I can see where I could simply spot solder it to the +B1 connection on the PCB, but where do you attach the ground? It seems to be a long run from my photo...
Thanks!
Rich
(http://www.sheltons.net/temp/psu%20top.jpg)
(http://www.sheltons.net/temp/psu%20btm.jpg)
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I don't see a spot on either side for the third cap, which I infer goes from +B1 to ground. Is that right, and if so, where did you attach it? I can see where I could simply spot solder it to the +B1 connection on the PCB, but where do you attach the ground? It seems to be a long run from my photo...
Well, these aren't in the schematic, but I had holes in my power supply PCB for the .47uf capacitors. They appeared to bridge across the power supply to ground (filtering). So... my amp(s) had holes present. They weren't immediately obvious. However, on both amps the holes were present. The 2nd time for the mods one of the hole pairs took me some time to find. These holes should be present on your amp too - unless the accounting department eliminated the holes to save more money :lol: .
Oh, you might have to look on both sides of the PCB for the holes. Someimes there is excess solder from other connections that will fill the empty hole on 1 side (normally the bottom) of the board. Generally the hole will remain visible from the top side of the board.
Dave
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Dave,
I have just ordered the parts from SonicCraft.
But, I have just realized that my amplifier has a 220V power-supply.
Since I have ordered some sonicap capacitors, I guess they are rated for 600V. Could it be a problem for my 220V amplifier?
thanks,
Pierre-Etienne
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You will have no problems. All amplifiers have a transformer to match the external (i.e. 220 or 110 volts) voltage to the desired voltage AFTER the transformer. The internal voltage will be the same. the parts you ordered will be fine.
Also, a higher voltage capacitor is never bad. Well, there are some issues, but for 99% of applications a higher voltage rating will have no downside.
Dave
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Dear all,
I have opened my 302B (bought in February 2005) but I am not able to see the holes for the 3 extra capacitors. Do you know if the schematic has been modified recently?
In the explanations, its seems that the "after" pictures, page 3 and 5 are reversed, like in a mirror. Is it possible or did I misunderstood something?
Since I am not expert, I may ask a stupid question: can I remove (unscrew) the PCB, or is it better to let them in place?
thanks again for your help,
kind regards,
Pierre-Etienne
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I am not able to see the holes for the 3 extra capacitors. Do you know if the schematic has been modified recently?
The holes do NOT appear in the schematic. The do appear on the vertical PCB holding the power supply capacitors, diodes, and resistors. You will find the holes in this PCB.
In the explanations, its seems that the "after" pictures, page 3 and 5 are reversed, like in a mirror. Is it possible or did I misunderstood something?
Yes, exactly. This is so that you can see the mods from both angles.
Since I am not expert, I may ask a stupid question: can I remove (unscrew) the PCB, or is it better to let them in place?
You will have to unscrew the vertical (power supply PCB) to solder some items. Work gently and you will be fine.
You should not have to unscrew the larger PCB.
If any of this isn't clear, please try to indicate where you need further help.
Dave
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Dear all,
as mentioned previously, I have applied the mods. suggested by Dave.
Everything went quite smoothly, except two things:
- the diodes were too short to fit in the holes
- I did not find the holes for the bypass capacitors.
Here the overall picture, where you can see where I have added some holes:
(http://pemoreau.neuf.fr/images/jolida302b/DSC_0510.JPG)
This shows the problem with the diodes:
(http://pemoreau.neuf.fr/images/jolida302b/DSC_0515.JPG)
This shows how I have connected the capacitor that goes from +B to ground (the hole exists on my PCB):
(http://pemoreau.neuf.fr/images/jolida302b/DSC_0512.JPG)
(http://pemoreau.neuf.fr/images/jolida302b/DSC_0511.JPG)
This shows how I have connected the capacitors that goes from +B1 and +B2 to ground:
(http://pemoreau.neuf.fr/images/jolida302b/DSC_0513.JPG)
(http://pemoreau.neuf.fr/images/jolida302b/DSC_0514.JPG)
I have carefully verified everything before turning the amplifier on, and this works great!
This sounds to be a big improvement with respect to the stock unit, but I have to continue my listening session :-)
Thanks again,
Pierre-Etienne
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Yep, it looks like the newer/different versions of the 302 don't have the holes for the capacitors. However, your insights are correct and your work looks very clean.
The diodes. I bent both legs of my diodes outward. Then at the very ends of the legs, they are bent straight down. I have bent some of them extremely without breaking. I believe the diodes leads are quite mallable. I suppose they could be broken, but I didn't break any.
Your work looks darn good. Please do convey your results about the sound quality improvements.
Dave
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Dear all,
Your work looks darn good.
I have to say that a friend (an electronician) helped me to perform the upgrade the amplifier.
Please do convey your results about the sound quality improvements.
Since I am quite new in this domain, I do not necessary have the correct terms to describe the impact of the modifications. I also have to mention that I am a bit skeptical about various things. But, I was curious to the see (or ear) the impact of electronic components.
To be honest, I am very surprised by the result.
The first thing that comes to mind is: precision. I do not know why, but everything become more distinct: you can more easilly discern the different musical instruments. The voice is also more distinct, like extracted from the musical background.
When you concentrate on sounds, they seem to be more defined in the sense that "they know where they want to go, and how they are going to finish". This remind me the notion of firmness. Similarly, the bass seem to be tight.
The main impact of all these phenomena is that the soundstage is larger and more precisely defined: you can more easilly ear a dialog between the instruments. This gives me the feeling that the artist is closer to me.
I do not have a big experience, but the last time I have felt this sensation was on an Accuphase E-406 (much more expansive than the Jolida).
As mentioned by Dave, this seems to be the best investment that you can do in Hifi. For $120, the Jolida 302B is transfered into a better category.
Thanks again Dave!
Pierre-Etienne
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Hello everyone,
when I came to meet pemo for buying a pair of Ellis 1801b, I could notice that he was using Jolida/EH 12AX7 and 12AT7 valves on his amplifier Jolida JD-302B. What a pity! So we changed "Jolida's tubes" for RCA 5751 -12AX7 sockets- and for Mullard CV4024 -12AT7 sockets-. I found the soundstage beautiful and wide opened, very "musical" indeed.
When, two months later, I came back to pemo's, for "recessing", improving tuning, the Jolida JD-302B was burning with "Jolida" 12AX7/ Mullard CV4024. Even if we changed the AOP in my Cayin CDT-17A, it was less magical than with RCA 5751.
If you are afraid of RCA 5751 (mu=70 vs 100 for 12AX7), please try the very cheap JJ/Tesla ECC-803S with long plates -not the E83CC-.
Kind regards, that's my two cents,
teiki.
Ps: as pemo is a pure skeptical scientist, he did not unfortunatly change the 12AX7 yet... 8)
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when I came to meet pemo for buying a pair of Ellis 1801b, I could notice that he was using Jolida/EH 12AX7 and 12AT7 valves on his amplifier Jolida JD-302B. What a pity! So we changed "Jolida's tubes" for RCA 5751 -12AX7 sockets- and for Mullard CV4024 -12AT7 sockets-. I found the soundstage beautiful and wide opened, very "musical" indeed.
I am not certain which "he" you are referring to, but don't think this was Dave Ellis.
I used Amperex Bugle Boy tubes (orange logo?) for the 12AT7 and 12AX7. I also had some Mullard tubes for comparison, but I don't recall which these replaced. I also had the OEM Jolida tubes. Anyhow, I did find a modest improvement when using the Amperex tubes and did prefer them over the OEM tubes, and the Mullard.
For the output tubes (i.e. El34s). I really enjoyed the Svetlana "C" logo models, but my Jolida 302 would "eat" 1 of these tubes about every 3-4 months. This became frustrating and I eventually returned to using the OEM output tubes. These didn't sound as good, but lasted very long. I don't have an explanation for the very short life of the Svetlana "C" logo El34 tubes in my Jolida 302.
I have learned that having a slow turn-on circuit, or delay will significantly improve the lifespan of tubes. The heaters really need to get started before the B+ voltage is applied. Unfortunately, 99% of tube amplifiers don't have this type of circuit. My Golden tube SE40 has an aftermarket switch to turn-on the heaters before the B+ voltage.
Dave
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FWIW, apparently those who have tested a LOT of EL34s are praising the virtues of the JJ EL34s, even over the Svetlana "C" wing type.
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FWIW, apparently those who have tested a LOT of EL34s are praising the virtues of the JJ EL34s, even over the Svetlana "C" wing type.
Thanks Josh, and indeed I have never tested these.
I have also learned that Groove Tube http://www.groovetubes.com/ actually has a very solid product, but they don't get much press in hifi.
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I am not certain which "he" you are referring to, but don't think this was Dave Ellis.when I came to meet pemo for buying a pair of Ellis 1801b, I could notice that he was using Jolida/EH 12AX7 and 12AT7 valves on his amplifier Jolida JD-302B.
No, "he" refers to pemo...Sorry not to have been more clear...
I used Amperex Bugle Boy tubes (orange logo?) for the 12AT7 and 12AX7. I also had some Mullard tubes for comparison, but I don't recall which these replaced.
I have tried dozen and dozen of 12AX7/5751, 12AT7/5965, 12AU7/5963 and 6922/E88CC tubes. Amperex 12AX7 are good for guitar amplifier but not as preamp tubes at all, IMO. I like very much 5751 in stead of 12AX7, especially RCA Black Plates triple or double mica or Sylvania 5751 GB...For a very good pair of 12AX7, JJ/Tesla ECC803S long plates is a an excellent Quality/Price choice...
That's my two cents.
Best regards.
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Thanks very much for this input. I must admit NOT being a tube expert.
Dave
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Hi Dave,
Here's my version of 302a. Link shows B1 & B2 top and bottom view.
http://www.audiocircle.com/index.php?action=gallery;area=browse;album=850 (http://www.audiocircle.com/index.php?action=gallery;area=browse;album=850)
Doug
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Hmmmm,
You are missing some holes in your board. Bill (Response Audio) and I have corresponded about this, and a few other changes over the lifeline of the Jolida amplifiers.
You have 2 choices.
1. Omit the bypass capacitors.
2. Solder the leads of the bypass capacitors directly to the terminals of the big capacitors on the bottom side.
I think the latter would be fine, but if you ship the amplifier UPS, they might get ruptured loose. You could use .1uf capacitors (instead of .47) for bypassing. These will be physically lighter and less likely to break loose in shipping.
Dave
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A Retraction.
The holes are visible in 1 photo, but not the other. They are "buried" under the power supply electrolytics. Yes, you can put the bypass capacitor across these vacant holes.
Dave
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Hi Dave,
I just picked up a used 502a a week ago and have been floored by this inexpensive purchase ever since. Replacing the 10yr old original pre-amp / driver tubes brought a great improvement and I'm waiting for my KT88's for the power tubes.
Your Jolida mods web page with the before and after pic.s inspired me to look 'under the hood' of this amp and conclude that I could indeed handle replacing a few caps,some of the resistors and the volume pot myself. I am an electrician (not an electronic tech.) but I do solder my own cables and have replaced selectors and such in pre-amps. I know what a restor, capacitor and transformer do - but I don't yet have a complete concept of how an amp circuit works (I'm reading up on it though).
My thought is to put premium caps where they will do the most good (sonicap platinum?)
and regular sonicaps in the other positions. When looking at your site and reading the response audio upgrade info I got confused trying to figure out which are the coupling capacitors and which are the signal ground caps- and which ones I should spend the premium bucks on.
You show the .47uf caps as well as the .22uf caps as both being coupling capacitors.
the Response site lists these components as upgrades:
.22uF VH Audio V-Cap Teflon capacitors installed in the coupling locations.
.47uF VH Audio V-Cap Teflon capacitors installed in the signal ground locations.
Could you clarify that, and add your opinion as to wether the platinum's are worth the premium and where they would do the most good? You can reference the red and blue
circles on your web page .
Thanks so much for sharing this information with us - and for your web page.
-Noam
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Since I have ordered some sonicap capacitors, I guess they are rated for 600V. Could it be a problem for my 220V amplifier?
This is no problem.
The difference between your 220v amp and the USA 110V amp is the initial power transformer.
The internal voltages should be identical. The Sonicaps will be fine in this regard.
The only "hook" would be capacitors before the initial power transformer. In my recommended tweaks, there is nothing changed before the initial power transformer. Also, I am not sure if the Joilda has any capacitors before the initial power transformer.
Dave
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First, I have not compared the V-Cap and the Platinum. Hence, I really cannot be of any specific help in this regard. I believe both are good capacitors, but this is only via the rumor-mill.
Could you clarify that, and add your opinion as to wether the platinum's are worth the premium and where they would do the most good?
Well, I sold my Jolida primarily because it would toast a Svetlana C logo tube every @4 months. I also found the VanAlstine Ultimate 70 sounded slightly better than my Modified 302b. However, the modified Jolida tube amplifiers are very very good amplifiers, and certainly a product that could occupy a very good hifi system for 10+ years. Soooo, if you amp is reliable and you plan to keep it forever - sure, spend the extra $$ on some very good coupling capacitors. This makes good sense.
I think the standard Sonicap is an extremely good capacitor that doesn't cost much $$. In this regard, I think it's the smartest move for 99% of folks.
In the coupling locations in my source gear I currently have Mundorf Gold / Silver-Oil capacitors bypassed with .1uf Sonicap Platinums. Alternately, there are a few locations where I have Sonicap Platinums with no bypass (in smaller value locations). While this stuff does sound better, it's extremely expensive. I have @ $400 of these boutique capacitors in my system. This is not a value-oriented purchase. Sure, they are smoooooth, and clean, but the Sonicap is a very solid product.
I will also add that my source gear is essentially maxed out. It's filled with Black Gate capacitors, Superfast diodes, and some great tubes from Andy at http://vintagetubeservices.com/ (http://vintagetubeservices.com/). The only possible tweak remaining is adding @$100 of op amps in my CD player. I think 2111 is the designator, but I'd have to check my notes.
I haven't tweaked a Jolida 502, but believe the layout is very similar to the 302. As such, the locations where better capacitors would be most beneficial are the locations where the metalized poly capacitors currently exist. These are either round black (Solen) capacitor or square red/blue Wima capacitors. There should be 6 of them on your circuit board visible when removing the bottom plate. Check the values on the current capacitors and replace them with the same (or slightly larger if necessary) value Sonicaps. These are the RED and BLUE circles in the mod PDF.
I do NOT recommend using Platinums or VH caps for bypassing in the power supply. This would be totally wasteful.
Dave
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Please let me know if I missed anything.
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If anyone is thinking of a more radical mod, I came across this one that brings the 302 (a version) to class A triode no feedback operation.
http://users.podolsk.ru/boga/a_pre_drv1.html (http://users.podolsk.ru/boga/a_pre_drv1.html)
Aggressive to be sure but it may take the amp to the next level. I'm watching the 'bay for Jolida 302/502's now - beware my wife is a master sniper :wink:
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Hello Dave,
I hope you don't mind but I have to point out a correction in your mods as listed on the pdf list you provided.
You mention: "GREEN - Replace 4 OEM 10k ohm resistors with Mills MRA5 10k ohm resistors"
I have notice you also did this on your personal amp a while back. These resistors are the grid stop resistors and should be 1k ohm (up to 2.2k ohm at most) rather than 10k ohm. Using such a high value in this position would have an adverse effect on the frequency extensions and also not necessary to do it's intended job.
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That about covers it Dave, Thanks again. I will probably go with the regular sonicap gen II's all around for starters and see what I get. That and the volume & selector switch. Gotta leave some kind of upgrade path for the future anyway - what else would we have to obsess about? This amp is already a killer improvement over the various SS stuff I've had running my Vandy's anyway. (This rig has me listening to opera fer goodness sakes - I never listen to opera)
re. RA's (Bill's?) post
" I have notice you also did this on your personal amp a while back. These resistors are the grid stop resistors and should be 1k ohm (up to 2.2k ohm at most) rather than 10k ohm"
I haven't 'read' resistor values yet but I do have a band reference color chart. These are the resistors that come of the tube socket bases, correct ? RA I take your word seriously as you mod these things for a living.
Noam
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I haven't 'read' resistor values yet but I do have a band reference color chart. These are the resistors that come of the tube socket bases, correct ? RA I take your word seriously as you mod these things for a living.
Yes, these are the resistors that go from the power tube socket to the circuit board. The schematic value is 1K ohm. I do like the Mills but prefer a good Carbon unit such as the Riken Ohm for grid stops. You can use anything from 1/2 watt up in this position.
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There are normally several Jolida amps for sale at www.audiogon.com . I have purchased several pieces of gear from audiogon with great success.
Dave
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I have notice you also did this on your personal amp a while back. These resistors are the grid stop resistors and should be 1k ohm (up to 2.2k ohm at most) rather than 10k ohm. Using such a high value in this position would have an adverse effect on the frequency extensions and also not necessary to do it's intended job.
I didn't change any typology or values when swapping compoents in my 302. I simply upgraded resistors from the elcheapo OEM units. I think it's very possible that factory amplifiers were shipped with a few different configurations. I have been told by folks in-the-know this is a very frequent occurence.
I also think that Bill knows these amplifiers, and his comments are safe. I also know that amplifiers will vary across production lines. I have seen this before.
Dave
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I too have been working on redesigning the Jolida 302/502 amplifier circuitry. I want to do away with using the 12AX7 input tube. This amount of gain is not necessary and I have found other tubes (with the proper circuitry) can sound amazingly good. There may be a new version of the Bella EXtreme 3205 sometime in the first quarter 2007!
I haven't tweaked a Jolida 502, but believe the layout is very similar to the 302.
Identical other than bias resistors.
CAPACITORS:
Well, I have played with a countless number of coupling capacitors in these amps. Here is my break-down:
1) Sound on the warmer side - AuriCap or SoniCap Gen II (they pretty much sound the same)
2) More precise but without the same level of warmth - SoniCap Gen I or Theta AudioCap
3) Seductive presentation - Jensen or Audio Note PIO
4) The best in refinement and overall most musical presentation - SoniCap Platinum or V-Cap.
Any one of these capacitors will bring forth noticable enhancements in these amps. I prefer to take them "all the way" but this requires completely gutting the amp and building up from the bare chassis. The prototyping of the new circuit is proving to be exceptional and I hope this will become our next 3205 Statement product. Time will tell.
Have fun with your Jolida and enjoy the ride.
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1) Sound on the warmer side - AuriCap or SoniCap Gen II (they pretty much sound the same)
2) More precise but without the same level of warmth - SoniCap Gen I or Theta AudioCap
3) Seductive presentation - Jensen or Audio Note PIO
4) The best in refinement and overall most musical presentation - SoniCap Platinum or V-Cap.
I agree with all of these comments, but have not auditioned the V-Cap. My preference is the Sonicap Gen I for most things.
Hello Dave,
I hope you don't mind but I have to point out a correction in your mods as listed on the pdf list you provided.
You mention: "GREEN - Replace 4 OEM 10k ohm resistors with Mills MRA5 10k ohm resistors"
I have notice you also did this on your personal amp a while back. These resistors are the grid stop resistors and should be 1k ohm (up to 2.2k ohm at most) rather than 10k ohm. Using such a high value in this position would have an adverse effect on the frequency extensions and also not necessary to do it's intended job.
?? Uh, er ??
I posted my schematic here: [http://www.ellisaudio.com/302b.pdf (http://www.ellisaudio.com/302b.pdf), and the value listed is 10k ohms for R13 and R16. My amplifier was had the same values installed, and I replaced them with the same values.
I am not an EE, and generally make very safe decisions. Presumably you have experimented with this and found a smaller value superior? Please confirm.
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I didn't change any typology or values when swapping compoents in my 302. I simply upgraded resistors from the sand-cast OEM units. I think it's very possible that factory amplifiers were shipped with a few different configurations. Also... I don't think the value of these resistors was listed on my schematic. I thought they were the emitter cushion resistors, but I could be incorrect.
The emitter/cusion resistors (off the cathode of the power tubes) are 1 ohm units located on the center of the power supply board. You will find a black wire going from one end of the resitor to the cathode of the tube. This is where the bias reading is taken from. These have always been 1 ohm units except for the first 200 pieces of 302/502 ampliers ever built in 1994 which used 6922 input tubes. The value for the emitter resistors on these units was 10 ohms. (different input circuit and transformers as well) If the value of the "emitter/cushion" is changed, the whole opperation of the output tube changes.
The Green circles you have on your diagram are the grid stop resistors. These are located between the coupling capacitor and grid of the output tube. These resistors are to stabalize the circuit to control oscilation. Using a higher value will not hurt anything but they should be no higher than 2.2K for performance.
I also think that Bill knows these amplifiers, and his comments are safe.
Thank you for that Dave. Please don't take offense to my comments but I am very familiar with these products and have custom built over 700 of them over the past 9 years.
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Sorry Bill, I had to check my work. I think we are overlapping at the keyboard while posting. Yep, the green ones were the grid-stop units.
These resistors are to stabalize the circuit to control oscilation. Using a higher value will not hurt anything but they should be no higher than 2.2K for performance.
Ahhhh, okay. This makes good sense. The factory installed 10k ohms when only 2.2k ohms is necessary.
Dave
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Yes Dave, we did end up with some overlapping.
Ahhhh, okay. This makes good sense. The factory installed 10k ohms when only 2.2k ohms is necessary
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I have never seen this happen but it is obviously very possible. Someone may have reached into the 10K bin of resistors instead of the 1k bin when assembling the amp. The schematic calls for 1K units. I have installed 8k-10k pieces just to see what the circuit does. Not realy pretty.
By the way Dave. From what I understand, this amp once belonged to you. It was sent in for further upgrades including turning it into a straight power amp and going with the Silver face.
(http://www.responseaudio.com/_borders/full.jpg)
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The schematic calls for 1K units. I have installed 8k-10k pieces just to see what the circuit does. Not realy pretty.
Again, my schematic calls for 10k ohm resistors. http://www.ellisaudio.com/302b.pdf (http://www.ellisaudio.com/302b.pdf) Is this wrong?
That amplifier belongs to Kevin K. It wasn't mine, but I did the initial tweak. I am certain you performed the "complete Bill" set of mods :). Kevin mentioned there is no more PCB. This is very thick stuff - much more than I am willing to attempt.
Dave
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Again, my schematic calls for 10k ohm resistors. http://www.ellisaudio.com/302b.pdf Is this wrong?
Hmmm..... my apologies Dave. To be honest with you, I have never seen this schematic. I stopped using schematic a few years ago for these amps but always measure prior to replacing resistors and never came across 10k units here. YOu are absolutely correct on the value of the grid stops. I will have to remember to measure these resistors on the next "B" series amp I get in. Again, my public apology.
I just can't understand why they would use such a high value resistors here.
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Thanks Bill for the detailed impressions of the resistors and caps. On your site you mention that installing the v-caps is not for newbies. Is the sonicap platinum any easier to work with? It's less pricey than the v-caps and an easier sell should the wife notice the charges.
I solder my own interconnects and a few other things but you wouldn't want me as your circuit board surgeon.
re. resistor values. Interesting. I guess I will pull out the ohm meter and have a poke before ordering.
-Noam
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Strangely,
A greater truth is often derived following some degree of misunderstanding. For this, I am thankful :D.
My guess is that you obtained a slightly different schematic several years ago. This is fairly common. I was told by a Golden Tube SE40 expert there weren't/aren't any good factory schematics available for the SE40. There were 4 different SE40 schematics. All had errors, and all were not fully optimized :duh:. While Jolida is a much better company, there were probably changes in their typology over time.
If 1/2 watt 1k ohm is what you are using, I'll change my recommendations. Thanks for the input! I am certain you are abreast of these amplifiers :). Your results are very admirable.
Also, are you purveying these 302/502 amplifiers with some flavor of switch for the B+ or a slow turn-on circuit nowdays?
Dave
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Thanks Bill for the detailed impressions of the resistors and caps. On your site you mention that installing the v-caps is not for newbies. Is the sonicap platinum any easier to work with? It's less pricey than the v-caps and an easier sell should the wife notice the charges.
The V-Caps are exceptional. Unfortunately, the new series is too large to use in the Jolida amps without some circuit board surgery. The Platinums are also great caps and I think you would find them to be a worth the investment. Yes, they are a bit les expensive.
re. resistor values. Interesting. I guess I will pull out the ohm meter and have a poke before ordering.
ALWAYS A GOOD IDEA. Goes along with "measure twice, cut once". As Dave mentioned, things can change without notice within any given product line. There are some product out there where I have brought in 6-10 pieces without coming across and two that were identical.
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If 1/2 watt 1k ohm is what you are using, I'll change my recommendations. Thanks for the input! I am certain you are abreast of these amplifiers . Your results are very admirable.
Ya know what Dave... I would recommend a note to have people measure these resistors before making any assumptions. I think this would be a safer bet.
Also, are you purveying these 302/502 amplifiers with some flavor of switch for the B+ or a slow turn-on circuit nowdays?
Actually, I am working on a whole new power supply design for a mono bloc version of these amps. More on that later.
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Ya know what Dave... I would recommend a note to have people measure these resistors before making any assumptions. I think this would be a safer bet.
I updated the PDF document with a note encouraging folks to check the value for these resistors prior to replacement.
Dave
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Hello Dave,
Thanks for not biting my head off on this one. When it comes down to it. You were right.....plain and simple.
I think having DIY'ers check the value prior to upgrading these resistors is a good idea. The problem with high value grid resistor is a reduction in bandwidth but sometime it is better to sacrifice a bit of bandwidth to maintain stability within the circuit.
I will continue to bench test units before and after rebuilds and apply the best value that provides the best balance. To date, I have never had to use anything higher than 5k ohms. The goal is to apply the least amount of resistance that stabilizes the circuit.
Thanks again for the kind communications!
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No problem, :thumb: .
I also fully understand that you are trying to run a business and your commentary about my tweaks are fully charitable aa. Posting in this discussion string conveys significant truth about your excellent character.
I will add these comments to the plans. I think having DIY'ers check the value prior to upgrading these resistors is a good idea. The problem with high value grid resistor is a reduction in bandwidth but sometime it is better to sacrifice a bit of bandwidth to maintain stability within the circuit.
I will continue to bench test units before and after rebuilds and apply the best value that provides the best balance. To date, I have never had to use anything higher than 5k ohms. The goal is to apply the least amount of resistance that stabilizes the circuit.
Dave
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Thank you for your understanding Dave. Many manufacturers do not like it when dealers post on their forum. You have what is obviously a fine product and I can only hope to help your customers bring forth the full potentail from the speakers should they be looking at the Jolida based units.
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Well, I for one DIY-er appreciate both of you sharing your knowledge on this subject.
For what it's worth, - my original 502a resistors are marked as, and measured as 1K. (actually .998K)
I finally located the holes for bypass caps on my boards. I have the coupling caps on order - and as this is a component upgrade rather than a mod, I will do these first. I don't know if this is easily answerable (and feel free to point me elsewhere for basic knowledge) but in simple terms - what do the bypass caps do - why where they emitted on the original- and what might the sonic benefits be ? I do appreciate your time, so as I said , if this is more than either of you would care to get into I completely understand.
funny aside, - on the AVS forum audio section there is another of the heated age old "do amps matter" threads running on. I am trying not to take the bait and waste my time jumping in but listening to this Jolida on the Vandy's, after having had older McIntosh(125wpc) and newer Monster(250 very punchy/clean wpc) and an older adcom 555II amp on the system - there just is no question . Maybe I'm just in the first blush of over the top tube love - but I've fallen hard.
thanks again - Noam
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what do the bypass caps do - why where they emitted on the original- and what might the sonic benefits be ? I do appreciate your time, so as I said , if this is more than either of you would care to get into I completely understand.
Well, there are several aspects to this issue.
1. The smaller bypass capacitor is often a superior quality than the larger main capacitor. In the Jolida, the main capacitors are electrolytic, and the smaller capacitors (after you add them) are metalized poly. The latter will have less electrical series resistance. In this regard, the smaller capacitor is a "band-aid" that partially fixes the main capacitor.
2. The smaller bypass capacitor will have a shorter/faster time constant. This means that it will discharge faster. The result is that small ripples from the diodes or from you wall outlet will be filtered better.
There are other issues too, but these are the most prevalent IMO.
I was skeptical about the impact of the bypass capacitors and performed this addition/test in isolation. I found slightly cleaner bass and slightly cleaner midrange. The impact wasn't huge, but was audible.
Maybe I'm just in the first blush of over the top tube love - but I've fallen hard.
I don't believe you have "tube love". I think you have a genuine appreciation for a good amplifier. There are good SS amps too, but you don't have one. I am certain that if you would have auditioned/purchased a Nirvana+ AKSA that you would have also fallen hard for Hugh Dean :wink: . Hugh's amps are good too - oh yes.
Dave
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Thanks once more Dave. Your explanation makes sense. Sorry for the delayed response.
I will likely do the bypass caps in the second round. I've got most of my parts in at this point for the coupling caps, resistors and new volume pot (noble) and selector (elma) but I'm not sure when I'll get to the project. Perhaps next week.
Any guess as to how long a 'burn in' period I should give the sonicap platinum's ? I was thinking I would run them with an older but still usable tube set to save life on my newer tubes, -unless there is some reason not to.
Thanks for the tip on Hugh Deans amps. I will look into them. You never know what might come across your path in the future if you keep an eye out. The Aksa site did not fully load on my browser. Does he sell kits? I'm not convinced I could never love a ss amp. It's just that most of the stunningly palpable imaging rigs that have impressed me have been tube driven - and previously out of my price range. I have a separate home theater set up with hi-wattage mid-fi solid state gear and love it for what it does, including surround music. Creating 3D stereo magic is a tougher trick though- and this is the closest I've come.
I'll post again after getting the work done. - Noam
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Any guess as to how long a 'burn in' period I should give the sonicap platinum's ? I was thinking I would run them with an older but still usable tube set to save life on my newer tubes, -unless there is some reason not to.
I... didn't really hear any change during after using the Sonicap Platinums. The same was true with all of the Sonicap capactiors. If there was a change during break in, the change was extremely subtle.
However, I do hear significant change during break in with Black Gate (not applicable for these mods) capacitors. They seem mostly settled by 100 hours, and fully settled after 250 hours. They sound very murky, dull and thick initially, then become very clean by 250 hours. I can't explain this phenomena, but others seem to agree.
In either case, there is no reason to use less valuable tubes during break in.
Oh, I highly recommend purchasing tubes from Andy at Vintage Tube Services: http://vintagetubeservices.com/ (http://vintagetubeservices.com/) . Andy's historical and mechanical understanding of Vaccum tubes is phenomenal. His testing is extremely pervasive and precise. And, most importantly, Andy's tube's sound amazing! The most significant boon from Andy are his Old Stock (slightly used) tubes. A $45 set of fully tested Andy's (NOS) stock (used) 6SN7 Sylvania tubes easily replaced a $130 set of RCA Red Base tubes in my amp. I have purchased many other tubes from Andy and they are all VERY good performers at a very good value. Doing business with Andy is VERY wise. The only reason I would ever purchase a tube from another source is if Andy didn't have that tube in stock.
The Aksa site did not fully load on my browser. Does he sell kits?
Yep. I recommend the 100wpc Nirvana +. It's killer good. I think Hugh had one of these traveling around the country for audition. I suggesting checking his forum for this scoop.
But... the Jolida is a very competent amplifier too. And as you mention, It's just that most of the stunningly palpable imaging rigs that have impressed me have been tube driven - and previously out of my price range.
I agree herein, and will add that Hugh's Nirvana + amps deliver extremely well in this regard.
I will likely do the bypass caps in the second round.
If you do this, please comment on the impact of this implementation in isolation.
Dave
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Hi Dave , It's true - I've become addicted to sniffing solder smoke. It may partially explain my irrational behavior.
I upgraded in two stages.
Stage one;
Changed the stock coupling caps with Sonicap platinum's , upgraded the selector switch (Elma) and some of the input chassis wire -the pos.s from the input rca's to the selector and from selector to volume pot.
I thought changes where subtle but good.
There may have been a burn in thing that went on - I'm not sure, - but after some time I did have more of those "holy shit" moments where the palpable presence on some recordings was alarmingly good.
This weekend I did stage two ;
I installed 3 bypass gen 1 sonicaps. Upgraded to mills MRA5 1-ohm emitter cushion resistors and fairchild "stealth" diodes (rated 8 amp 1200 volt). Changed volume pot to Noble , bypassed the balance control and upgraded a little more of the chassis wire from the volume pot to the board. I did not change the stranded ground wire anywhere. Not from the inputs or to the board. Perhaps this is a mistake ?
Initial impressions where not great. Steelier more pronounced upper mids and highs, a little tighter mid-bass but what seems like an overall bass (80-400hz?) roll off. Imaging less "round". One of my current reference recordings is the Pizza Tapes with Tony Rice, David Grissman and Jerry Garcia. All acoustic guitar and mandolin. Tony's guitar tone has less of the woody resonance that "put it in the room" for me. Pick attack on steel strings more prominent . Voices a little more forward. More detail on Jerry's guitar. Not as seductive a sound though It may or may not be more accurate .
I swapped in my old tubes back in and I'm running for 100 hrs. to see if that magical mystical "burn in" mellows things to where I like them. I'm at about 60 hours and the basic character seems to be the same. It's darn good - just not as much to my liking as it was before.
If it doesn't enchant me after some time, I may want to reverse some of the changes. If you have an educated guess as to what I might try swapping back first - I'm all ears. I could probably get used to and enjoy most of whats happening on 'top' if I got some more back on the bottom. It's always hard for me to know (without a good spectrum analyzer) wether a perceived tone change is due to addition of one thing,-subtraction of its opposite,-or some of both.
I am enjoying this hobby. Now that I've got a decent soldering station and workbench going I may have to start building kits. Hope your holidays are going well.
Noam
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I have some thoughts, and will convey them tomorrow morning.
Dave
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Hi Dave, I think you are going to have to add Hugh's Life Force amp to your solid state recommendation list. The AKSA N+'s are very nice. But, the Life Force is just superb. I haven't heard your speaks. So, I cannot speak from experience. But, if the AKSA amps did well with the 1801's, then odds have to be huge that the Life Force will be even better -- outstanding bass (tight and big) and real extended and sweet highs.
Happy Holidays,
Steve
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But, if the AKSA amps did well with the 1801's, then odds have to be huge that the Life Force will be even better --
yes, I have to agree but I'll see if I can't post a review in the "what amp are you using" thread over the holidays. I think it is a beautiful match-up :D jim
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Noam S.
Thanks for being patient for my response.
My response will be divided into 2 parts. I will first comment on what the audible changes should be with my piece of the mods in part 2. I will then comment on what I would accomplish to fix your problems.
My hunch is that you do indeed have something wrong. Unfortunately, I cannot physically hear your amplifier. The underlying message I hear you conveying is that your amplifier sounds worse following the mods in part 2. This should not be the case. After the bypass capacitors and diodes, the bass will clean-up slightly (i.e. less round), and the midrange will also become very slightly cleaner. However, the difference is NOT dramatic. If the impact sounded significantly wrong/bad, it probably is wrong/bad.
I did not fuss with the balance control, and have never accomplished this. I am not certain of the complexities, or what happens if things go awry.
I have experienced what happens if diodes are backwards. Normally smoke will result :duh:. Either the diode or something after the diode will clearly indicate a clear problem. However, if you have a bad/weak solder joint, the result could be a thin sound. But, this is only a guess.
My first step would be to check the orientation of the diodes and the viability of the solder joints. My next step would be to undo the balance control. After this, work backwards and INDIVIDUALLY undo your work in part 2.
I became quite zealous with my CD player and swapped @ 40 parts in 1 sitting. I had 2 bad solder joints, but couldn't find them. I managed to isolate the location via schematic, but couldn't find the problem. After 4-5 hours of looking analyzing the problem I decided to send the CD player to a pro. He found the problems, but it cost me $250. My wife wasn't happy :nono:, and I promised to never fuss with my CD player again. However, all of those Black Gate caps sound ooooh so smooth!
Oh, I should also offer herein a comment about coupling capacitors that would seem germane to 302 mods. I now have Mundorf Silver/Oil and Mundorf Gold capacitors in a few locations of my source gear. These are good capacitors and sound slightly better than the Sonicap, but not significantly better. IMO, the Mundorf capacitors are NOT a wise value-oriented purchase. IMO, the Sonicap offers 90% of the performance at 20% of the cost. In retrospect, I... probably should not have spent $300 on the Mundorf coupling capacitors in my source gear.
I am using a Sonicap Platinum .1uf bypass around all the larger coupling capacitors in my source gear. This is a slightly better value but not "huge". As such, my recommendation for this is positive, but not overwhelmingly so. But, these aren't terribly expensive. As such, installing .1uf Sonicap Platinums around the coupling caps in the Jolida 302 is a reasonable option. Perhaps someone could comment herein after deciding to accomplish this.
Dave
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Hi Dave,
No problem re. the delay. With the holiday season you are hopefully doing more important things like selling speakers and enjoying family & Friends.
After giving up on the 'burn in' after about 80 hrs. I decided to remove the bypass caps as a first step because a) they are the easiest to get at and un-do and b) they are a circuit change vs. a component upgrade.
This has made a considerable improvement to my ear. There still are a bit more pronounced highs and upper mid's than there was originally and it is cleaner overall I think. Most of the warmth and presence of individual instruments has been restored. Jerry and Tony's guitars both sound really good now.
It is possible that I had placed the caps in the wrong holes (there where more holes than cap leads) but I'm pretty sure I got it right. The pictures in your very appreciated tutorial can't show every hole clearly -so I studied the board for a while before I understood what & where the ground circuit trace was and what the bypass caps where supposed to be bypassing. It is still possible I made an error though.
The diodes look the same and are in the same direction as Pem shows them in his pic.s on page 2 of this thread and correspond to what my meter readings on the original diodes told me - though they do read different on my digital meter.
I think my joints are good. I give them all a light wiggle test or two, and the solder looks like a clean shiny mini-puddle. This last bunch of mod.s was soldered with my new Hako at 700 degrees farenheit.
(nicest soldering tool I've ever used) That said, I am still new at this circuit board soldering and it certainly is possible that a bad joint got by me.
On the balance pot bypass I simply took the L & R leads from the output of the volume pot and went straight to the board with them - where before they went through the balance pot first. I think that the balance set in the middle = o ohms resistance (or very close to it) to each side passing through it(-though I will double check that on the removed control when I get a chance-) so bypassing it should be the same as the neutral position on the control.
I think I may do a little tube rolling with the amp as it is for now, and see how it dials in.
After that I may or may not decide to reverse some of the other changes.
When I get a chance I will take some pics of my board and indicate where I had the bypass caps if I can.
On another subject; - Do you have any vendors for your speakers in or near San Francisco ? I would love to check them out sometime.
Enjoy your holidays and thanks for all your help. - Noam
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This has made a considerable improvement to my ear.
Well, it could be that your amplifier has more potential holes than many others. And... you somehow managed to bridge A/C juice from + to - this would cancell, and cause audible problems without creating any smoke. Sometime in the next few days I'll add a note regarding this issue in my modification plans.
I am aware that some 302b amplifiers don't have the holes for there bypass capacitors. Hence, there are obvious changes across production runs for these amplifiers. It may be true that your amplifier has holes that appear in the correct proximity, but the wiring layout of the PCB changed.
I think a fair and reasonable solution to this issue is moving the location of the bypass capacitors. They could be physically attached to the bottom side of the PCB on the same posts as the electrolytic capacitor(s). Unfortunately, I don't the amplifier to illustrate this method via photos. Bummer.
Anyhow, I do appreciate the input and feedback regarding this issue.
Oh, regarding tubes, I recommend contacting Andy at Vintage Tube Services for some tested old-stock tubes. They won't be terribly expensive, but the sound quality will be very good. I believe Q.C. via testing in tubes is very important, and Andy accomplishes this very well.
It sounds like you have a good soldering iron and good technique too. A nice shiny color is very desirable :thumb: . This is much easier with a thermostatically controlled soldering iron.
Dave
Dave
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On another subject; - Do you have any vendors for your speakers in or near San Francisco ? I would love to check them out sometime.
Well, ahem... A vendor??
Any decent vendor isn't willing to work for $0/hr, but perhaps they might be interested in profit sharing :thumb: . This would often infer an hourly rate slightly less than $0/hr :lol: .
I actually do consider this hobby a blessing. I manage to buy a few tools every ear, get great compliments from those who build the 1801, and... I generally break even financially. How many guys can convey this about their primary hobby?!
I believe there are 1-2 1801 owners in the S.F. area, but this was a few years ago. It would take me hours of digging through paper to maybe find them - IF they haven't moved.
Your only possible means of audition is getting on the audition list. The current wait is @ 4 months, and you are obligated to ship the 1801s to the next listener. This will cost you @$70. Most folks keep the touring 1801s for about 1 month.
Dave
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Ah - I see I was unclear on the concept.
Any decent vendor isn't willing to work for $0/hr, but perhaps they might be interested in profit sharing :thumb: . This would often infer an hourly rate slightly less than $0/hr :lol: .
That's not a bad rate. The guys in my band get paid the same figure. I of course get double that for enginering producing and mixing down our sessions.
I actually do consider this hobby a blessing. I manage to buy a few tools every ear, get great compliments from those who build the 1801, and... I generally break even financially. How many guys can convey this about their primary hobby?!
That is great. I'm just lucky "she who must be obeyed" indulges my predilection to spend more time making and listening to music (and fussing with the gear) than I do earning income. - Putting in a new closet organizer the other week helped greatly in this regard.
I believe there are 1-2 1801 owners in the S.F. area, but this was a few years ago. It would take me hours of digging through paper to maybe find them - IF they haven't moved.
If you stumble across their emails let me know - no hurry. Always nice meeting more audio wackos (no reflection on their taste in speakers) in this area. I'll talk with my other audio buds about going in on an audition - re-ship deal down the line.
I will get in touch with your tube man.
take care - -noam
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That's not a bad rate. The guys in my band get paid the same figure. I of course get double that for enginering producing and mixing down our sessions.
:lol: :lol: Very true!!
Dennis Murphy www.murphyblaster.com (http://www.murphyblaster.com) is not allowed to have any income from his speaker building hobby due to is position as the Govt "Godfather" for audio standards and enforcement in the USA. He commented that he loses much less money playing in the local Symphony than building speakers. However, both are a accomplished at a financial loss.
I enjoy the rest of your comments too. It would appear we both have a very healthy marriage :thumb: .
Dave
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back to the original issue;
My hunch is that you do indeed have something wrong. ....I did not fuss with the balance control, and have never accomplished this. I am not certain of the complexities, or what happens if things go awry. ........ My next step would be to undo the balance control.
I played some material that I know has some more pronounced bass and realized that there was still a major suck-out of the low freq.s Put it back on the bench and per your sage advice took another look at the balance circuit. I was wrong about how it works. It does not present variable resistance to the signal in and 0 resistance at neutral. It instead shunts variably to ground. (My understanding such as it is -is from ohm meter readings - not the schematic) At neutral it is still 50k ohm to ground each side. Not having 50k ohm resistors on hand I re-installed it in the circuit. What do you know - the bass is back !
Someday I hope to understand why this would have the effect it did but for now I am happy to be back on track. I will listen for a while before putting the bypass caps back in - to garner what I can about the specific difference that operation makes. Good call Dave - thanks again. - Noam
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What do you know - the bass is back !
Congratulations!
Fortunately, you were able to make an error that wasn't terribly expensive. A few of my soldering errors have resulted in ancillary components going up in smoke :duh:.
Dave
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Not having 50k ohm resistors on hand I re-installed it in the circuit. What do you know - the bass is back !
Hi Noam, Glad to hear your amp is back producing good bass once again but I am not sure it was the instalation of the balance control that did this. I have worked on these amps for years and 90% of them had the balance removed with no ill effects on the bass. It's hard to say what the actual cause was but at least you are back to normal.
In regard to bypass capacitors in the power supply, I would solder the leads direct to each main filter cap and keep the leads of the bypass caps as short as possible. Same goes for coupling capacitors, you want minumum lead length.
The Jolida amps have a LOT of potential hiding in them, have fun with your journey!
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Hi Noam, Glad to hear your amp is back producing good bass once again but I am not sure it was the instalation of the balance control that did this. I have worked on these amps for years and 90% of them had the balance removed with no ill effects on the bass. It's hard to say what the actual cause was but at least you are back to normal.
It sounds like you have a good soldering iron and good technique too. A nice shiny color is very desirable :thumb: . This is much easier with a thermostatically controlled soldering iron. ...
Dave
After reading me boast about my newly developing soldering technique - perhaps the correct response would have been "me thinks thou hath protesteth too much"
On the aduio asylum tube DIY board DanL suggested that a poor ground connection may have caused unwanted capacitance and acted as a high pass filter. When I re-installed the balance pot I did in fact re-do the ground connections at both the board and the volume pot - seeking to connect the balance control ground at one spot, then the other. Soldering to the pot pins was the trickiest for me because it was not easy to establish a mechanical connection before soldering. What that may have meant was that though the connection seemed strong, the wire may not have been making any direct contact with the pin - but only through the solder. - Might this have been the real culprit ?
I may snip the balance control out again as a test. As I'm thinking about it (a dangerous proposition given my limited knowledge) the 50k ohm to ground on both sides of the balance control should just be attenuating the signal slightly on both sides evenly. - Is there any reason it should be affecting low-pass ? - Bill, When you bypass the balance pots - do you install any resistor connection to ground or do you feed the board directly from the volume pot ?
thanks to both of you. - Noam
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Hello Noam,
I did see your post on the Asylum and did respond in regard to the "Emitter Cushion" resistors.
It does sound like you may have has a cold solder joint in the circuit when you removed the balance pot. This happens and the results are often a thin sound and very often some noise associated with it.
In the past, I would go from the volume direct to the input. I found no need for any shunt resistors. To date, I probaly have about 300 or more of these in consumer's homes. Recently, I have been adding an attenuation circuit as the 12AX7 input stage has what I believe to be more gain than is needed in the design. Another option if you find to much gain is to use a 50K pot rather than the 100k pot that comes standard in the Jolida products. You are not changing the circuit but you would get more range in the control. I use a TKD 50K pot in Big Blue which is my "test amp" for new upgrades. It has been torn apart and rebuilt countless times over the years. It was built from teh ground up from a bare chassis. It now uses the 12AU7 input tube. SEE BELOW
You may want to do yourself a favor and completely bypass the controls and wire direct to the board and use an active preamp. BIG difference. Depending on the preamp used, you will still need to attenuate the signal slightly.
Those are now behind me as I have redesigned the input curcuit and optimized it for the use of 12AU7 input tubes. My new Bella EXtreme 3205 MKII amplifiers will now use this circuit. I still use a divider in these as they are now staright power amps.
Here's an older picture of BIG BLUE before the input stage modification.
(http://www.responseaudio.com/_borders/bigblue.jpg)
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Sound is stellar right now. As promised, -this amp is now up in new territory. What was really good has become extrodinary. I've been enjoying a lot of music and am resisting the urge to "make it even better".
Besides re-soldering the grounds and balance pot (and probably fixing a cold joint in the process) I tried some Kimber chassis wire on two inputs. I had put solid core Wonder Wire (from the solder folks) on the inputs previously. The Kimber is MUCH warmer. A bigger difference than any cable swaps I've tried. Something was wrong with that WW - (or my connections-?). I experimented with the bypass caps in and out. Did not hear an obvious difference and left them in.
In the tube dept. I found (to my surprise) that I like the original equipment 6550's better than the EH KT88's I had bought. Cymbals and such ring truer - overall top end clarity is better. On everything but the harshest recordings it is still fairly non-fatiguing. (I have a mild allergy to metal dome tweeters - which the Vandy's have. Love the detail–hate the bite). Tried Groove Tubes 12ax7-M’s which are pretty good, but went back to the long plate JJ’s. The combo with the old 6550’s just sings in this rig. I will eventually try other tubes but for the moment I’m trying to resist the urge to mess with what’s working.
Picked up a 302a this weekend. Un-mod-ed it is much more veiled than the mod-ed 502a though I haven’t done much tube rolling yet or had a chance to listen extensively. Also picked up a nice old pair of spica TC-50’s to play with. – any mod-ing suggestions there ?
Bill – The Noble volume pot I put in is 50K.
re. Bypassing all to the board and using a pre-amp;
Would I go the same place on the board as the controls are feeding now? Do I bypass a pre-amp (12ax7?) section of the amp or is the pre-amp section of this amp completely passive and the 12ax7’s part of the power amp section?
Any bargains in the used pre-amp category I might keep an eye out for ? I’m familiar with the standard Audio Research, Classe, CJ, etc. I hadn’t heard of Jolida till my 502 came up for sale and I did a search on it. Any equivalents in the pre-amp department ?
Happy New Year - Noam
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Also picked up a nice old pair of Spica TC-50’s to play with. – any mod-ing suggestions there ?
Well, there I heard a story about the Spica 50. Once upon a time it was a great speaker and enjoyed commensurate success. Then the high quality declined when someone purchased Spica for @100k and forced the engineer to stuff cheap and very poor Q.C. Chinese drivers in the cabinet. It became a very mediocre speaker at this point, and eventually the frustrated engineer/builder departed ways with the new owner and his implementation of the cheap Chinese drivers in a speaker that WAS very good.
So, if you have an older Spica - great. If you have a newer Spica - sell it and find an older one. Unfortunately I don't know the specific details regarding production numbers and years of production.
IF you have an older Spica 50, the only change I would make is swapping the series capacitor. It probably has a Solen. This could/should be replaced with a sonicap. Don't mess with anything else - unless a magnet will stick to the binding posts. This indicates ferrous material present - most likely the nuts. Replace the ferrous nuts with some brass nuts. Or, replace the post assembly with the cheapest Cardas post possible. These don't have any ferrous material and are very sturdy.
FYI I re-thread a $2 Chinese post for use with brass nuts for the 1801.
Any bargains in the used pre-amp category I might keep an eye out for ?
This is a no-brainer IMO, even when matched against expensive preamps, the Scott Ender passive attenuator is VERY good. Additionally, they will be very viable with the @100k input impedance for the Jolida tube amps.
Sound is stellar right now. As promised, -this amp is now up in new territory. What was really good has become extraordinary. I've been enjoying a lot of music and am resisting the urge to "make it even better".
:thumb: This is how it should sound. :D
I suggest getting the smaller value tubes from Andy at Vintage Tube Services. Whatever he has in Used Old Stock is the smartest IMO. They are well tested and perform dandy. And, they are quite cheap.
Dave
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Greetings. I am new to these boards but have already noticed a wealth of information, particularly for myself in this thread. For about a little over a year now I have been the proud owner of an Antique Sound Labs AQ-1002 which was my first foray into tube equipment.
For several years a friend and me have been talking of building our own amps, and he has in fact put together a pair of basic, but functional tube guitar amplifiers. we recently decided to begin simultaneous audio amp projects. He chose a basic single ended design, and I chose to closely emulate the Jolida 302B.
I have been in electronics calibration and repair most of my adult life, but am not of the engineering ilk. I have decided to build the 302B with the mods built in from the ground up, and this is all relatively new to me.
I wonderred if I could ask a question or two of some of the posters on Mr Ellis's thread, and perhaps even Dave if you so choose to answer. i completely understand that your business is not in educating the hobbyist and take no offense if you decline to comment.
I am just beginning to acquire components and will likely do so over the coming weeks. I decided there is no adventure in an exact replica, so i have chosen a pair of Hammond 1650R 100W output trannies and a Hammond 378CX 400-0-400 power tranny. I am planning on putting the full anticipated rectified output of about 550-570 on the El34's to maybe squeeze the clean output power into the 60-70W range. I will make adjustments as seems logical to component ratings in the effected circuits.
So initially I had two questions.
Has anyone successfully tried to juice the El34's voltage to gain output power in this amp, and if so what might be some roadblocks?
Secondly, i was rather disappointed in the availability of high quality electrolytics for the power supply. All the old classics seem obsolete, and I'd like to keep the cost to under $20 a piece. The only decent option I've found so far in that range is a pair of Evox Rifa's at 470uf 450V for the first set.
Thanx in advance for any time taken to read my post and any responses. Audio is a labor of love. The only audio board I've ever used extensively is the Polk Audio board, and I have found the audio enthusiast community to be very close knit and helpful.
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I apologize for my slow response.
I must first admit that I am not an amplifier designer. While I can easily recognize the Williamson push-pull design in several different forms, it would take me considerable work to design an amplifier starting with nothing. Some modifications are easily within my grasp, but I leave the thicker stuff for those who are enthusiastic about this stuff. I am a speaker-guy at heart.
However, the linear gain curve (mu) for any tube is reasonably easy to read with some study. In this regard, if a tube is pushed to swing a greater distance for greater gain there will be more distortion. In my opinion, an EL34 has a reasonable output of 30wpc in a push-pull configuration. If you wish to have more output while using only a pair of tubes, I suggest a design using KT-88 tubes.
Secondly, i was rather disappointed in the availability of high quality electrolytics for the power supply. All the old classics seem obsolete, and I'd like to keep the cost to under $20 a piece. The only decent option I've found so far in that range is a pair of Evox Rifa's at 470uf 450V for the first set.
Unfortunately, most good products have a commensurate price tag :roll:. Occasionally there are bargains in any realm, but I don't know of any in the capacitor realm. The good stuff is more expensive. There is a reasonably summary of electrolytic capacitors here: http://www.tnt-audio.com/clinica/ssps3_e.html (http://www.tnt-audio.com/clinica/ssps3_e.html). Aside from this, Black Gate does make a 100uf 500v capacitor. There are also some slightly larger metallized poly capacitors from Angela or SCR. But... this stuff isn't cheap (or small). Also, for a power supply, you could certainly cascade bypass some less expensive electrolytics, and use metalized poly for the smaller values.
I do admire you desire to build a tube amplifier. Everyone knows that tubes sound better :wink: .
I do have 2 solid suggestions in this realm. Neither may be welcome, but they are my opinion.
1. Buy a kit from someone where you can obtain good support. // I believe this is one reason why Hugh Dean (AKSA) does very well).
or
2. Buy something you can tweak. There are plenty of Dynaco mod projects available. I own a modified ST70, and it sounds VERY good.
I again apologize for my slow response. Hopefully you find some of this helpful.
Dave
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Hopefully I can ask this question. How do you compare underwoodhifi mods to others? :scratch: I dont know much abour modifications nor I have the skills or patience to do them. Some of us depend on mods services to perform the job, especially those that are not technically savy such as myself. Anyway, wanted to ask about the differences that some retailers/modification services offers?
I know I have a Jolida JD 100 with a level 2 mod however I have not own a stock JD 100 so I cant really compare the differences. Also, I have the 1000RC GREAT integrated amp especially with upgraded tubes JJ, Mullards and EH. When time and money allows I will like to get my amp modded... :green: aa
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Hello chgolatin2,
I hope I am not out of place posting here. If so, please feel free to delete this post David.
Being a Jolida modifier, I am obviously very familiar with Walter's (Underwood HiFi's) modifications. I am not familiar with other Jolida modders. What I can tell you is that he is very much respected in the industry. The differences in the modifications come down to just that.....differences. I have known Walter for many years as well as spoken to him on a few occasions. I feel we have a mutual respect for each other and have never clashed or butted heads.
We are both after the same thing, an enhanced performance from high valued products. The difference is in the presentation as we both have a different sound that we are after.
Take for instance the JD100 player. The Underwood mods go in the opposite direction from ours. With our mods, we go for a warmer, more seductive presentation while bringing forth more in regard to resolution & transparency but adding a bit more midrange texture. Underwood's mods bring the player closer to a more analytical, cleaner presentation opening the window to more inner detail and upper end extension.
I have heard his player and there are several out there that have heard both his and ours. It boils down to personal preferences and maybe even price for some. We try to enhance the player while keeping the price very reasonable, well under the $1500 mark.
With the amplifiers, it is the same line of thought. We both try to enhance the performance but again, in different directions.
Please don't mistake this post as self promotion or an "ad" as I do not even work on the JD1000RC. I was only trying to describe the different goals and directions of two modders.
I can recommend Walter for the mod of your JD1000 but as mentioned, I am not familiar with the work of any other Jolida modders that might be out there.
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Dave
Thank you for the reply and no worries on the delay. I am still researching and acquiring parts. You know I agree 100% (on paper) that a kit is the simplist most logical way to go. Then again I have this stubborn I want to do it myself voice in my head, and well...it often wins the arguement. Yes, I am planning on bypassing the electrolytics with Poly's so I am coverred there, I was actually referring to the sad fact that Elna Cerafines, Blackgates, Nich Muses etc, seem to all not be made anymore driving up the cost of remaining stock. It is what it is, obviously not a deep enough market to continue manufacturing them.
I have done a lot more research and agree the KT88's would get me in the power realm I want, but I already have my AQ-1002 KT-88 amp which runs like a champ. I'd really like to do an EL34 amp and get the power up, but also realize they don't do well above 25 watts power dissipation. So that being said, and pardon my testosterone driven logic, the obvious answer is I need 8 of them :green:
Take the advice of my girlfriend...."Don't argue with him when he's like this, he won't hear you" :lol:
So that being said I would dearly like to know if you know where a schematic of the Jolida JD-1000A or JD-1000RC can be had. I will gladly pay for a copy of I can find a source. I would greatly appreciate any help on this matter. Thank you for your time Dave, and if I don't burn the house down I will glady share with you any wisdom I gain from the endeavor.
Best Regards
Brian
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How do you compare underwoodhifi mods to others?
Candidly, I don't know anything about underwoodhifi.
Bill Baker has a great reputation. I have heard a few of his products, and concur with his methods that I understand. We also have a similar preference for capacitors.
Then again I have this stubborn I want to do it myself voice in my head
I experienced this voice too, but the voice was "talking" about speakers. After a few thousand hours I was able to build a product. After a few thousand more I was able to build a very good one. In this regard, I am sure you will eventually be able to build an amplifer. Considerable determination, and a few brain-cells will eventually matriculate positive results.
Blackgates, Nich Muses etc, seem to all not be made anymore
As of 3 months ago, a fairly significant retailer told me that Black Gates are still being made. They are expensive, but perhaps the construction methods warrant this cost. I really don't know how they are made. I only know how they sound.
Obtaining a schematic of my Jolida 302b was quite easy. I called the company and they faxed the schematic. I don't recall a fee, but there may have been a fee. Other companies will mail a schematic. Expect to pay about $30 for the schematic.
Presumably your current amplifier has a reasonable grade coupling capacitor. I suggest you install some sonicap platinum's in your current amplifier in the coupling circuit.http://www.mcmlv.org/Archive/HiFi/AntiqueSound-AQ1002.pdf (http://www.mcmlv.org/Archive/HiFi/AntiqueSound-AQ1002.pdf). It appears there are 4 .22uf coupling capacitors "begging" to become sonicap platinum's.
Dave
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If you're looking for HV electros, have a look at Mundorf caps. Very good quality. Lots of info at www.mundorf.com and Parts Connexion (www.partsconnexion.com) carry them (among others). Parts Connexion also have other available at differing prices. And I am not a related party to either company :D
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Also picked up a nice old pair of Spica TC-50’s to play with. – any mod-ing suggestions there ?
Well, there I heard a story about the Spica 50. .....
Hi Dave.
A little follow up on the used TC50i with the Joli. Picked a clean pair up for $200 months ago. Tried them briefly and heard some of their imaging potential but the lack of upper detail caused me to put them in storage till I had time for some experiments. First experiment done this week for the heck of it; - swapped the tweeters for a pair of scan-speak 2905/9500 's that I had gotten years ago for my ultimate mini-monitor project that never got built. Almost a perfect physical fit but had to hand saw away a teeny bit of the cabinet to squeeze them in.
Anyway -- Freekin amazing sound !!! I have an old subwoofer in the mix a little too but that asside - the Spicas with the modded Joli 502 are producing scary imaging you could cut with a knife. People are looking around for my none existent hidden surround speakers. My good buddie the Maggie-phile, who's speakers produce a cinemascope size soundstage, and who loves to put down sound from "boxes", was dumbstruck. He now gets the "imaging thing". There is more 3D spacial information than he has ever heard and I have maybe heard a few times before (Snell w/ VTL , Thiel w/Classe Audio Research etc.) The Vandy 2ci's are good in this regard but this combo is nutz. The scan-speak tweets seem to be a great match in the Spica's. Oogles of detail withouth metal dome bite - and they have only been played about 10 hours so far. Haven't replaced caps yet and I'm not in a rush as I am still amazed with what's going on as it is.
Anyway - the modded Joli is shining away.
We (Rich the Maggie guy) and I recently toured some hi-end systems with the BASS (bay area audiophile society ). I also heard Wilson / VTL set up in the hi-end room at a local boutique. If someone gave me all this cost no object stuff I would sell it (though some of it looks awfull pretty). I'd actually rather listen to what I've got -and go on tweaking classic audiophile bargains with minor mods as they come along.
I will eventually need help with a 302 I picked up that had been hacked & butcherd. It's on the bench but haven't had the time to dig in yet. - take care - Noam
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I would dearly like to know if you know where a schematic of the Jolida JD-1000A or JD-1000RC can be had. I will gladly pay for a copy of I can find a source.
Perhaps I thought that Bill would address this, but... I certainly am able.
I suggest calling the national Jolida rep in Maryland for a schematic http://www.jolida.com/contact/index.shtml (http://www.jolida.com/contact/index.shtml). They faxed a 302 schematic to me in quick fashion a few years ago. They might charge $20-$30 for the schematic, but this is minor.
//
Noam,
Congratulations on your success with the amp and Spica's :thumb: !! Yes, there is potential therein, and it appears you got lucky with the SS9500 tweeter. A direct driver swap without crossover mods is normally negative, but the SS9500 tweeter is a good unit. It doesn't have the most detail of the SS9900 tweeter, but many folks prefer the smooth character of the SS9500.
I don't generally visit many commercial hifi shops anymore. I think my most recent visit was 3-4 years ago. This is primarily because we share the same sentiment regarding the common gear. Sure, it looks pretty, but I'd rather listen to the stuff in my own listening room. And... my stuff looks okay.
I suggest upgrading the coupling capacitors in the amp before upgrading the capacitors in the speaker.
Dave
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Perhaps I thought that Bill would address this, but... I certainly am able.
Sorry guys. This one got past me. I try to keep up with most threads here regarding Jolida pieces but since I don't receive email notifications, I loose a few.
Anyway, I don't have a schematic for the 1000A but can tell you that the circuitry is identical to the 302 with the exception of the additional output tubes.
With the newer LED bias, things are a bit different in the bias stage.
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It should be noted for others to benefit as well is the combination of tubes i used for the Jolida sj502a, the power tubes can be maximized by using a variation of the 6550 tubes, namely the center being the v4 and v8, and the ends if you will being the v3 and v7 . I use a for the v4 and v8 the 6550 eh electroharmonix, and for the v3 and v7 use the svetlana 6550c. The result is that the amp delivers lets say the remaining possible best output by using this combination. I found this by accident and was pleasantly surprised.
With this combination you seem to get the best of both worlds say.
Norm
I am about ready to try some new 6550's in my Jolida. I had liked the (well used) 6550's that came with the Joli. I replaced them with some EH KT88's that aren't as detailed and bodied in the highs -though otherwise very nice. How would you describe the sound you got from the different tubes - and what the combination is doing for you ?
thanks, Noam
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Hi guys.
What are your preferences between 6550 and KT88?
Currently I'm running my JD801A with Svetlana KT88 output tubes. I've never tried 6550's. What should I expect if I were to try a set?
Thanks.
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I found that the old oem 6550's (I don't even know what brand) that came with the amp when I got it - had more detail and body in the upper mids and highs. Ride cymbals for instance, resonated in a very lifelike manor that was not as good with the EH KT88's. I didn't notice much difference in other aspects on my rig.
I had the Vandersteen 2ci's when the 6550's where in. For the moment I have a modded pair of Spica TC50's in. I am getting some very holographic imaging with this set up (with the KT88's) but do want to try some 6550's again with these speakers - to see what happens. I may also experiment with some of Norm's mix n match suggestons. Some day soon I will just listen to music again - I did for a while there anyway.
-Noam
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Succinctly, I found I got more rich and detailed sound , as I mentioned by separating the power tubes. The svetlana's 6550 on the ends and then the eh 6550 , both, in the middle. Incredible lush sound. I have not tried the kt 88's. However, I suspect if one were to alternate them like the 6550's , your output would be for sure richer on octave or two.
Given the push/pull nature of the amplifier, the positive and negative swings of the amplifier have a different character due to the different tubes being used. It could also be true that the phase connection has shifted slightly when using different tubes for the positive and negative swings. So, while you may appreciate the sound, it could be rooted in distortion.
Dave
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There are still a few folks performing the mods on their 302B/502 amplifiers per my instructions. I wish to offer a some commentary about things that I have learned and some specific feedback about the impact of the diodes.
First, Bill Baker really knows these amplifiers and mentioned a while ago that there are subtle circuit board differences, and installing power supply bypass capacitors isn't readily possible in some amps. This is because there aren't any holes in the vertical power supply circuit board for these bypass capacitors.
Second, a few folks (not many) have used my general recipe to modify other Jolida amplifiers. One gentlemen recently worked through his 502. After installing the coupling capacitors he offered the following comments regarding the impact of upgrading the power supply diodes:
Dave, just wanted to let you know the stealth diodes make a huge difference. I don't measure my gear so it could be the placebo effect. I don't care what it is, the sound is much more engaging and less fatiguing even on the dreaded CD's. Thank you for the help you brought my amp up to a very high end sound at a low price. I can't wait to do the phono stage. Parts are on the way.
Just so you and your readers know, the latest version of the 502brc has seven diodes. Thats right I found two more sneaky little ones hiding when I took the power supply psb out. It goes like this(I think), two 5408's coming in from transformer, one 1n4007 going to the bias, and four 1n4007's leading to and from a plug with two wires leading to the amp section. I was two diodes short so I guessed at which ones were the least important and changed the rest. I think I guessed right because the sound is great. I have to order the other two today.
I have also accomplished diode swapping as an isolated modification to one of my pieces of source gear (I don't remember which piece). I don't think I found a HUGE impact, but certainly an impact that was obvious. Yes, replacing diodes does matter. There are differences in rise time and recovery character. Oh, and there is also a problematic issue about transient ringing that is on the fringe of my knowledge. There is a difference between a .02c diode found in most source gear an a good Harris/Fairchild Gen 2/3 unit. Jeff at www.soniccraft.com has the latest iteration (Gen 3) flavor of these diodes. They are in a TO 220 format and are therefore slightly tedious to install, but easily worth the $15-$20 cost for a set of diodes to upgrade an amp/preamp/CD player. A set of these diodes has easily more positive impact than a $800 set of speaker wires - IMO.
I know there are certainly some folks who convey that diodes shouldn't matter. And I suppose that with enough power supply filtering and a clean waveform from the power company (yeah right :roll:) that a better diode might not have the same impact. However, in varying degrees, better rectification via diode performance will have a positive impact in source gear.
While I am primarily a speaker guy, I cannot ignore the profound impact source gear has on the signal. Upgraded components in source gear are critical for anyone striving for better sound in their living room.
Dave
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Hi,
Firstly this post may not be very relevant to the thread. I have a Jolida 1501 RC and had recently replaced the stock 12AX7 tubes with mullard. There was a significant improvement. This together with what I have read makes me believe that analogous mods such as done by you will help. The problem is I am from India and its not feasible for me to get it modded by a reliable third party (mostly in US) so I intend to do it myself. For that I need the schematic for 1501RC (for which I had sent a mail to Jolida but got no reply) or some advise/suggestion on mods on this particular model. I would be grateful if someone can help me on this.
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Prasen,
First, it has been my experience that swapping/upgrading coupling capacitors has far more impact than swapping tubes. Other mechanical mods have less impact, but they remain very significant.
Second, I have absolutely no idea what is lurking under the hood of your amplifier. I have never puttered with a Jolida Hybrid. Further, you might have problems that are deeper than what "should" be present. Bill Baker has been the Jolida mod expert for many years, and I fully trust his commentary regarding Jolida amplifiers. Following Bill's remarks on this webpage http://www.responseaudio.com/AboutResponse.htm (http://www.responseaudio.com/AboutResponse.htm) my believe is that your amplifier may not follow the schematic valid for folks in the USA and perhaps there isn't a trustworthy schematic simply because the components in your amp were chosen somewhat randomly - with VERY poor attention to quality control. This was certainly the case for many Golden Tube amplifiers.
So, I am really not sure that your amplifier is a candidate for mods in the same fashion that Bill or I approached the mods for the Jolida 302. :cry: I am sorry, but I don't have a solution or direction for you.
Dave
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Thanks for the reply Dave.
Following Bill's remarks on this webpage http://www.responseaudio.com/AboutResponse.htm my believe is that your amplifier may not follow the schematic valid for folks in the USA and perhaps there isn't a trustworthy schematic simply because the components in your amp were chosen somewhat randomly - with VERY poor attention to quality control. This was certainly the case for many Golden Tube amplifiers.
From this I suppose u r talking abt the commentory made on the chinese made Jolida products. I am not sure where it was made but the product was bought from an authorized Jolida dealer (Cadence - Pune Maharashtra). I will ask the dealer about it or check the unit itself. Also I have compared this unit with Cyrus 6VS2 as well as NAD pre/power combo both of which are costlier and it has performed better overall. Irrespective of this scenarios if I could get a schematic I could get some idea about which are the coupling capacitors (my target was just replacing/adding the coupling/bypass capacitors ) in my unit atleast. As I have mentioned I had sent a request for a schematic to jolida with no response. And ur comment that the swapping/upgrading coupling capacitors bringing a significant improvement makes whatever risk involved much more worthwile. So my main aim is to get the schematic and then work out the implementation feasibility.
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I will ask the dealer about it or check the unit itself.
Hmm, I suggest asking the dealer to obtain a schematic. They will likely have better success.
Dave
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I asked the distributer about the schematic he said he cannot share it. But he is ready to talk to jolida and see what mods could be possibly done and may also do it for me. Keeping my fingers crossed.
I also opened up the amp and looked through, most of the electorlytic capacitors in the power supply as well as the output stage were rubycon USR series. Did the 302 amp had the same manufacturer's caps? The firm seems to have a good reputation.
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Hello prasen,
We did not do much with the Jolida hybrid amplifiers other than completely redesign the circuitry in conjunction with another designer. I believe [one] of the reasons Jolida would not want to provide a schedule is to keep it from hitting the internet such as some of their other products did.
Another situation is that amplifiers designed for North America are different from those for the rest of the world so I cannoteven say what potential yours may have.
In general, some of the more significant upgrades would be as follows: (in no particular order) 1) Change out the stock silicon diodes in the power supply for a good quality 'Ultra Fast - Soft Recovery' type. 2) Change main coupling capacitors on the analog board. I won't even recommend a capacitor as it is far to subjective and personal. 3) Critical resistors on the analog board. 4) Add bypass capacitors to the main filter capacitors in the power supply. 4) Internal signal wire from RCA inputs to controls and then to circuit boards.
Keep in mind that these are just general guidelines to upgrading this unit. Your choice of components will determine the final outcome but don't think that just because these areas use upgraded parts that it will be a guaranteed improvement. Sometimes a lot of trial and error is required to get the desired results.
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I received a query regarding further mods for this unit. My response follows:
There are three more 302b possibilities for improvement that I am aware of.
1. Bypass the 4 circuit board coupling capacitors (.22uf) with a .022 Sonicap Platinum capacitor. These are the capacitors circled in blue. http://www.soniccraft.com/sonicap_platinum.htm .
2. Bypass the 2 circuit board coupling capacitors (.47uf) with a .047 Sonicap Platinum capacitor. These are the capacitors circled in red. http://www.soniccraft.com/sonicap_platinum.htm .
3. You may already have very good tubes, and if they are surviving - GREAT ! The 302b was difficult on tube longevity. However, you might be able to obtain slightly better tubes from Andy http://vintagetubeservices.com/contact.htm . This guy is wonderful and profoundly knowledgeable. I highly encourage you to purchase his used & tested tubes. They will be fairly inexpensive, and perform perfectly. Andy will want to know about your amplifier and the tubes you currently use. You will need to contact any via telephone.
Please report your results herein.
Dave
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Dave, if I were to do just one set- the .47 or the .22 to begin with; which would make the most difference?
Thanks!
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Hi Wire Nut,
The .22uF are the actual coupling capacitors. the .47 are signal ground. You will definitely want to start with the .22uF.
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The .22uF are the actual coupling capacitors. the .47 are signal ground. You will definitely want to start with the .22uF.
You da' man :thumb: . Thanks Bill !!
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I have ordered the upgraded caps in the .22 value. I will let everyone know how they sound.
Thanks for the great advice! :thumb:
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I....
...Actually recommended purchasing and using a .022uf bypass around the .22uf primary capacitor, BUT if you can afford the $$, using a .22uf Sonicap Platinum would probably be better. I haven't performed this experiment and cannot comment.
Dave
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Dave,
I was just going to replace the white SoniCaps with the Platinum. Will that work? I had purchased some Mundorf but read that the SoniCap do not mix well- so your suggestion for the Platinum sounded like a great idea:
http://www.humblehomemadehifi.com/Cap.html
Thanks
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I was just going to replace the white SoniCaps with the Platinum. Will that work?
Definitely! It will probably work better. I didn't recommend this initially because most gents prefer an easy fix and prefer a less expensive solution.
Also, while I have never a/b tested the difference between a single Sonicap Platinum and bypassed configuration (i.e. primary Sonicap Gen I and bypass Sonicap Platinum), when Jeff modified my Golden Tube SE40SE, he used a single Sonicap Platinum in at least 1 location for a coupling capacitor. So, my hunch is that using a single Sonicap Platinum should work better.
I can also convey that in 1 coupling location my amplifier I removed the @4uf Sonicap Gen 1, and replaced it with Mundorf Silver/Oil. In another Location in my CD player, I replaced the Sonicap Gen 1 with a Mundorf Gold capacitors. Both of these capacitors were bypassed with a Sonicap Platinum before and after the primary capacitor swap. In retrospect, I don't recommend this. The Mundorf Silver/Oil and Mundorf gold capacitors were quite expensive (@$300), and I am not sure if they sounded better. There were some tonal changes, but I couldn't convey clear superiority.
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Hi Dave, I hope you don't mind me jumping in here and feel free to correct me if you don't agree.
I was just going to replace the white SoniCaps with the Platinum. Will that work?
If you can swing it, I would recommend replacing the coupling caps with .22uF SoniCap Platinum rather than doing any bypassing on coupling capacitors. I am not a fan of bypassing coupling caps for various reasons. If using the Platium, there would be no need to bypass anyway. These are well worth the cost of the upgrade.
To be honest with you, I have not used the upper end Mundorf (Silver/Oil or Silver/Gold) in the coupling positions of this amplifier. I have used them in many other applications in the coupling position and do very much like these caps.
I would not say they are better or worse than the Platinum but definitely different.
You can used the Mundorfs, SoniCaps or any other good quality capacitor to bypass the power supply capacitors (470uf x2). If you have extras, also bypass the B+2 supply. These will be somewhere around 150uF-220uF. Use one on each cap.
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Great!
The guy that owned it before me did all of your mods- plus; new Goldpoint pots, remove the balance, new tube sockets, etc.
I wanted to do a little to make it "my own" so I have purchased a pair of Vampire RCA input jacks & am waiting for some 22 awg pure silver ribbon hook up wire to replace the CD wiring on the unit. I also had walnut front & sides made... but the guy that did the laser thing included the word "Balance" so in honor of the platinum SoniCaps I will have a tiny plaque made that says "Platinum" in a script writing to cover it with.
I have put B-Quiet on the bottom inside & built am isolation stand out of hardwood that have also helped.
Just for fun I purchased Michael Wolff RCA's & a power cable for it- all in all it should sound & look great!
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For all- here is some good advice Dave gave on cleaning up the old solder:
De-soldering tips.
- I have tried a few different wicks, and prefer Chem Wick
http://www.all-spec.com/1/search/all/chem-wik?gclid=CIidru3bspoCFQVxFQodOlkmbw
And this product.
http://www.mgchemicals.com/products/400braid.html?PHPSESSID=950d0d2382c237b8aef884c7fe8f91be
If your de-soldering wick leaves considerable residue, buy a better wick.
The process.
1. Remove as much residual solder from the terminal area as possible.
2. Apply heat to the individual leads and GENTLY pull with a needle nose pliers. I have pulled too much and removed traces from circuit boards.
3. Either apply heat when re-installing the new component OR use a very small diameter drill bit to remove the excess solder in the circuit board hole.
The process is very simple, but I encourage you to be quite gentle and work slowly. De-soldering takes much more time than installing components.
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Well I installed the Platinum caps with no incident :).
I have left the unit playing for 50 hours & can give a first report:
The music is much more "Open & airy" there is a lot more definition at every range of the spectrum. That was all as expected from the reviews... what I did not expect is deeper bass with more punch!!!
Holy cow, this is the best hundred and fifty bucks I have spent on my stereo.
I will post some more observations next week after 100 hrs of burn in.
Thanks for the great suggestion- it works.
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Holy cow, this is the best hundred and fifty bucks I have spent on my stereo.
Wonderful!!
Yep, good coupling caps can do amazing things. Great coupling caps (i.e. Sonicap Platinum) can be sublime. aa
And... I really don't know why more bass happens, but I noticed this too. It wasn't a subtle change.
Dave
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Dave,
What would need to be done if at some time I wanted to be able to use KT88 tubes in my 302b?
Thanks
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What would need to be done if at some time I wanted to be able to use KT88 tubes in my 302b
I really don't know. I do know that some folks have amps that will accomodate both tubes. I am fairly certain you could plug-in some KT-88 tubes, but I am not sure how long the the amplifier would function before it started to smoke.
Also, I am not sure the KT-88 tube actually sounds better than the El34. Yes, I am aware of the many variations. I am also aware that I haven't performed a really good a/b test in the appropriate amplifier. But, I did hear my speakers on some push pull KT-88 tubes, and thought it sounded better on my Svetlana El-34 Jolida at home. Certainly there are many variables involved, but I perhaps it's fair to offer 1 crude data point.
Dave
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What would need to be done if at some time I wanted to be able to use KT88 tubes in my 302b?
The Jolida 302 and 502 are the exact same amplifiers with the only difference being in the value of 4 resistors that allow proper biasing points for the EL34 or 6550/KT88 tubes.
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Could you tell me what those 4 resisters are & what the value would be to have the ability to play both 77 & 88?
Thanks so much!
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Could you tell me what those 4 resisters are & what the value would be to have the ability to play both 77 & 88?
Thanks so much!
since it's been quite a few months since the above post, you may have already found the answer, or abandoned the quest, but based on the generic 302/502B schematic, those numbers would be:
R14 &15 (and whatever numbers would apply to other channel)
302B = EL34 = 12K
502B = KT88 = 24K
This of course still doesn't answer your question if the KT88 operating points would be in an optimal region for KT77,
BTW, has anyone tried the Steve Deckert CCE mod on their 302? This mod is effective for that small group of power pentodes with internal separation between suppressor grid and cathode. (e.g. the SV83 / 6N15N, or EL34).
In the case of the 302, it would mean replacing the jumper between pins 1&8 with a 1mF film cap. I have yet to complete this on my own triode wired 302, but have received confirmation from the owner of a modded Dyna ST70 that it worked wonders.
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Could you tell me what those 4 resisters are & what the value would be to have the ability to play both 77 & 88?
What I have found to work nicely is a 15k in this position. This has allowed me to use most EL34, KT77, 6550 and KT88 tube types.
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Guys, where would this 15K go? The reason I ask is I tried a set of the Gold Lion 77's and my unit would not work at all, I could not get a bias reading!
Thanks
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I thought I'd join the forum as I'm helping Chris with his 302.
I hope you mean 1?F and not 1mF Chris!
Cheers
EDIT: It would appear this forum does not support extended ASCII. The "?" should be a Greek letter mu.
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I thought I'd join the forum as I'm helping Chris with his 302.
I hope you mean 1?F and not 1mF Chris!
Cheers
EDIT: It would appear this forum does not support extended ASCII. The "?" should be a Greek letter mu.
well, as by now you've seen the piece - those are 1mF Solen films, IIRC
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Guys, where would this 15K go? The reason I ask is I tried a set of the Gold Lion 77's and my unit would not work at all, I could not get a bias reading!
Thanks
Well, just as there appear to be at least 2 versions of the power supply PCB, there may also be an uncertain number of variations on the main board containing the input/driver and output stage bias circuits.
Dave / Bill can correct me on this, but on both versions of schematics that have been posted in this thread, I believe you'll find them at R14 and R15 (i.e. between the bias trim pots and ground bus). In the case of my 1990 oops - that should be 1999 vintage 302B, they are clearly labeled on the PCB.
So in other words, you'd replace what ever value of fixed resistor is resident that site ( i.e. according to schematics posted elsewhere could be either 12K or 20K for 302 with EL34s)
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Chris: mF is millifarads, while uF is microfarads. There are 1000uF in 1mF, so it is best to be clear.
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I did a bonehead thing and failed to bias my tubes causing a meltdown of my left channel transformer. I decided it would be a good idea to upgrade the transformers and chose Hammond 1650 P based on reading a post somewhere. I have a slight problem with the install though. The Hammond comes with 2 more wires for impedance. The Jolida transformer had 1 brown 8 ohm wire, one Blue 4 ohm wire, and a black 0 ohm wire. The hammond transformer has 2 wires for 4 ohms and 2 wires for 0 ohms. How would I go about soldering the new amp with what appears to be a duplication of wires?
Thanks,
booker
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Check the hammond data page for the 1650P:
http://www.hammondmfg.com/1608.htm
The wiring diagram shows two separate interleaved windings, one with a single 4ohm tap, the other with the 4 and 8 ohm taps. The intention of the designer here is for the two 0ohm and 4ohm wires to be put in parallel; IE: Green to Green/Yellow and Black to Black/Yellow for all situations requiring a typical 4 or 8 ohm output setup. For 16 you end up wiring it all differently, but in the case of keeping the JoLida original, the former wiring configuration is desired.
Once you've wired the two four ohm pairs in parallel, you'll end up with three output wires, 0-4-8, as you need for your application.
Hope this helps! :)