[David Ellis]

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  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

[Bill Baker]

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.

[Noam S]

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

[David Ellis]

Strangely,

A greater truth is often derived following some degree of misunderstanding.  For this, I am thankful  .

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  .   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
 

[Bill Baker]

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.

[Bill Baker]

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.

[David Ellis]

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

[Bill Baker]

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!

[David Ellis]

No problem,  .

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

[Bill Baker]

 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.

[Noam S]

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

[David Ellis]

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  .  Hugh's amps are good too - oh yes.

Dave

[Noam S]

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

[David Ellis]

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/ .  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

[Noam S]

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

[David Ellis]

I have some thoughts, and will convey them tomorrow morning.

Dave

[blizzard]

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

           

[fajimr]

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     jim

[David Ellis]

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  .  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  , 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

[Noam S]

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