We91a - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th July 2004, 08:47 PM   #1
diyAudio Member
 
powertriode's Avatar
 
Join Date: Jun 2004
Location: South East
Smile We91a

Hi All,
I have decided that my next project will be a WE91 copy of some sort.
I have searched this forum and rec.audio.tubes and most of the links I have come across are dead.
I have found some good sources; however; which are listed below, and will be known to many of you:-

http://www.bonavolta.ch/hobby/en/audio/300b_1.htm
http://www.bonavolta.ch/hobby/en/audio/300b_2.htm
http://www.angela.com/catalog/how-to/model.91.html
http://www.timebanditaudio.com/personal.html
http://www.fortunecity.com/rivendell...cy/Legacy.html

below is the original SP article:-
http://www.timebanditaudio.com/300b/WE91A.pdf
and below is a schematic of the real thing:-
http://www.audiosharing.com/archive/...df/No.91-A.pdf

I would rather like to build the version from SP, as this appears to be nearest to the original.
Although I am a little concerned at the lack of hum pots, or a DC filament supply.
Has anyone built one??

All comments will be most welcome, irrespective of which variant, however I am most interested in the SP version, which unlike the others, retains the 310A.

Which one did you build? What iron did you use? Which tubes? etc.
  Reply With Quote
Old 4th July 2004, 11:18 PM   #2
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

The amp in the first link you posted is well known over here and was sold as a kit by the french "La Maison De L'Audiophile" in Paris.

I had a listen to it on several occasions during the early nineties while I was over there on business and must say it sounded really good.
Especially on high effeciency speakers ranging from the modest Fostex 103 Sigma (hope I have it right) through more sophisticated horn systems, even in a small theatre they used during a hi-fi show.

What's even better is that with the advent of ever better passive components the amp can easily be improved upon as the basic circuit is still one of the best 300B SE amps I know of.

IIRC the OPT was a special order design made by Partridge and was sold under the reference TK4519 by that parisian shop exclusively.

WE91 INFO

WE91 AMP

Cheers,
__________________
Frank
  Reply With Quote
Old 5th July 2004, 12:35 AM   #3
diyAudio Member
 
jeff mai's Avatar
 
Join Date: Aug 2002
Location: Melbourne
Default Re: We91a

Quote:
Originally posted by powertriode
All comments will be most welcome, irrespective of which variant, however I am most interested in the SP version, which unlike the others, retains the 310A.
Have a closer look at the original WE schematic from the link you posted. You'll see that it does not use the 310A; it uses the 6C6.

Anyway, I've built a pentode driven 300B amp and tried a few different octal pentodes as input tubes. The list:

6SJ7GT
6J7G
1620
6SG7GT
C3m (*loctal)
6AC7
6SG7

They all had their charm, but I prefered the good old 6J7G and the remote cutoff(!) 6SG7GT.

Tips:
Use the smallest plate resistor on the pentode that gives you the gain you need with your system. Everyone takes a shot at the 6J7 because of the low current and HF rolloff, but if you can live with a 47K plate resistor instead of the 90K shown, it is very good.

Use a VR tube to supply the pentode screen instead of a voltage divider or series resistor. This was the biggest improvement in my amp.
  Reply With Quote
Old 5th July 2004, 11:13 AM   #4
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Default Re: We91a

Konnichiwa,

Quote:
Originally posted by powertriode
I would rather like to build the version from SP, as this appears to be nearest to the original.
I have experiemnted a little with the rather more complex cathode circuit shown for the original 91A. I think you should incorporate it, with exactly the values as shown.

Quote:
Originally posted by powertriode
Although I am a little concerned at the lack of hum pots, or a DC filament supply.
The original 91A/B used negative feedback in a loop to the screengrid of the first stage, this reduced hum a lot.

For a modern 91 you may need to add DC heaters to get things quiet enough.

Quote:
Originally posted by powertriode
Which one did you build? What iron did you use? Which tubes? etc.
I build a "91 Inspired" Amp based on the later J.C. Verdier designed Le Maison de l'Audiophile Amplifier (EL84 Driver, later changed to C3m). All supplies regulated. Sounded excellent and was absolutely quiet....

Link below, WARNING - Fortunecity site, popups and cookies galore....

The Legacy Poweramplifier - A "universal" DHT Poweramplifier by Thorsten Loesch

Sayonara
  Reply With Quote
Old 7th July 2004, 03:27 PM   #5
diyAudio Member
 
powertriode's Avatar
 
Join Date: Jun 2004
Location: South East
Default Re: Re: We91a

Hi All,
Many thanks to all for your valued comments.

Quote:
Originally posted by Kuei Yang Wang
[B]Konnichiwa,

I have experiemnted a little with the rather more complex cathode circuit shown for the original 91A. I think you should incorporate it, with exactly the values as shown.
Worthy of consideration, many thanks!
Quote:
The original 91A/B used negative feedback in a loop to the screengrid of the first stage, this reduced hum a lot.
Yes, I did notice this (shock/horror!!!!!)
Quote:
For a modern 91 you may need to add DC heaters to get things quiet enough.
I had intended to use DC, and that is still the path I will likely go down.
Quote:
I build a "91 Inspired" Amp based on the later J.C. Verdier designed Le Maison de l'Audiophile Amplifier (EL84 Driver, later changed to C3m). All supplies regulated. Sounded excellent and was absolutely quiet....
The TK4519 is still available from Partridge, however I intend to use the TH4663, which is basically the same but cased. You have to order them and they make to order, only down side is the 10 week wait for delivery

I will get the Partridge OPTX's on order and when they come I will bread board it, and have a play.

I too noticed the orig circuit uses the 6C6; I wonder when this changed to a 310????

BTW, If you want to look at the real thing, click on this link:-
http://members.jcom.home.ne.jp/nedra/91.html
  Reply With Quote
Old 7th July 2004, 07:44 PM   #6
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
I too noticed the orig circuit uses the 6C6; I wonder when this changed to a 310????
Isn't it the other way around?
IIRC the WE91 used a pair of 310As...

BTW, in case anyone's interested I can still get some Russian NOS 310A with socket and gridcap.

Cheers,
__________________
Frank
  Reply With Quote
Old 7th July 2004, 08:06 PM   #7
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichiwa,

Quote:
Originally posted by fdegrove
Isn't it the other way around?
IIRC the WE91 used a pair of 310As...
Not till the "B" version. The original WE91 shipped with 6C6, the WE 310 was not available at the time IIRC.

Quote:
Originally posted by fdegrove
BTW, in case anyone's interested I can still get some Russian NOS 310A with socket and gridcap.
Interesting. How close do they sound to the WE's?

Sayonara
  Reply With Quote
Old 7th July 2004, 08:17 PM   #8
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
Not till the "B" version.
Ah...I see....
All the "La Maison de l'Audiophile" versions are based around the "B" version.

Quote:
Interesting. How close do they sound to the WE's?
To my taste the Russian ones compliment the sonic fingerprint of the WE300B even better than the WE310A, i.e. it's a little dryer, a tad less romantic if you like.

Cheers,
Attached Images
File Type: jpg 310a.jpg (24.0 KB, 1222 views)
__________________
Frank
  Reply With Quote
Old 7th July 2004, 09:43 PM   #9
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichwa,

Quote:
Originally posted by fdegrove
Ah...I see....
All the "La Maison de l'Audiophile" versions are based around the "B" version.
Not really. They use the same tube complement, but the circuit differs much.

Just for fun, my current state of ideaplay for a "modern" 91, complete (replete?) with feedback loop and a few other things....

Click the image to open in full size.

Quote:
Originally posted by fdegrove
To my taste the Russian ones compliment the sonic fingerprint of the WE300B even better than the WE310A, i.e. it's a little dryer, a tad less romantic if you like.
Interresting. Best take this off line....

Sayonara
  Reply With Quote
Old 7th July 2004, 10:41 PM   #10
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

T.,

It looks as if there's a drawing error in the diagram:
On the 310A g1 and g2 are tied together.

Cheers,
__________________
Frank
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
WE91A Pentode Questions? sgerus Tubes / Valves 11 7th August 2007 02:03 AM


New To Site? Need Help?

All times are GMT. The time now is 08:10 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2