[David Ellis]

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  .  This is much easier with a thermostatically controlled soldering iron.

Dave

Dave

[David Ellis]

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  .  This would often infer an hourly rate slightly less than $0/hr .

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

[Noam S]

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  .  This would often infer an hourly rate slightly less than $0/hr .

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

[David Ellis]

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.

    Very true!!

Dennis Murphy 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  .

Dave

[Noam S]

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

[David Ellis]

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   . 

Dave

[Bill Baker]

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!

[Noam S]

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  .  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

[Bill Baker]

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.

[Noam S]

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

 
 

[David Ellis]

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".

    This is how it should sound.   

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

[Zen Audio]

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.

[David Ellis]

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 .  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.  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  .

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

[chgolatin2]

Hopefully I can ask this question.  How do you compare underwoodhifi mods to others?    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... aa

[Bill Baker]

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.

[Zen Audio]

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       
 Take the advice of my girlfriend...."Don't argue with him when he's like this, he won't hear you"     
  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

[David Ellis]

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.  It appears there are 4 .22uf coupling capacitors "begging" to become sonicap platinum's.

Dave

[smithy666]

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

[Noam S]

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

[David Ellis]

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.  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  !!  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