We91a

[powertriode]

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/xentar/1179/projects/legacy/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/western/we_amp/pdf/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.

 

[fdegrove]

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,

 

[jeff mai]

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.

 

[ThorstenL]

Konnichiwa,

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.

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.

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

 

[powertriode]

Re: Re: We91a

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

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!

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!!!!!)

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.

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

 

[fdegrove]

Hi,

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,

 

[ThorstenL]

Konnichiwa,

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.

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

 

[fdegrove]

Hi,

Not till the "B" version.

Ah...I see....
All the "La Maison de l'Audiophile" versions are based around the "B" version.

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,

 

[ThorstenL]

Konnichwa,

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....

An externally hosted image should be here but it was not working when we last tested it.

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

 

[fdegrove]

Hi,

T.,

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

Cheers,

 

[agent.5]

If one is to design a "modern" version, just wondering what you guys think about some kind of CCS loaded for the 301A and 300B? Also how about using some higher voltage tubes, such as 845, 813, etc, instead of the 300B?

 

[MIKET]

WE310A

Hi,



Ah...I see....
All the "La Maison de l'Audiophile" versions are based around the "B" version.



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,

Where can one buy the Russian 310A?
I would love to get my hands on a couple.

 

[ThorstenL]

Konnichiwa,

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

You is right. It was supposed to look like that:

An externally hosted image should be here but it was not working when we last tested it.

Sayonara

 

[ThorstenL]

Konnichiwa,

If one is to design a "modern" version, just wondering what you guys think about some kind of CCS loaded for the 301A and 300B?

Absolutely not. CCS loading on pentodes is a way to make the gain silly high and maximise distortion, not what we want at all,

CCS on the Output stage? Maybe, but what for?

Also how about using some higher voltage tubes, such as 845, 813, etc, instead of the 300B?

Then it would not be a 91 and of course, the 310A would not be able to drive the output valve competently.

The 91 is what it is and has many merist. If you don't want a 91, fine, design something else.

Sayonara

 

[MIKET]

How about using an EL822 driver?

Would the EL822 be a good pentode driver for a 300B?

 

[agent.5]

Konnichiwa,



Absolutely not. CCS loading on pentodes is a way to make the gain silly high and maximise distortion, not what we want at all,

CCS on the Output stage? Maybe, but what for?



Then it would not be a 91 and of course, the 310A would not be able to drive the output valve competently.

The 91 is what it is and has many merist. If you don't want a 91, fine, design something else.

Sayonara

All right, I think you have a point and I should stick to WE310A as driver and WE300B as output tube. However, I still wonder if CCS is necessarily a bad thing. The reason i ask is that I am looking at another 300B circuit and it uses tons of CCS and I think CCS can provide additional linearity on triode, but then why not pentode too?

http://home.pacifier.com/~gpimm/300b_rev3.htm

So, how about replacing the 26 with 310A supplied with 2ma@190V? 2ma is from the following 91a schematic

http://www.diyparadiso.com/proj/maison300b.htm

Furthermore, 300B is run at 615V. Will higher voltage be better or worse?

 

[ThorstenL]

Konnichiwa,

However, I still wonder if CCS is necessarily a bad thing.

Well, as you know, a Pentode is most linear into a "zero" ohm Load and most distorted into a high impedance load. The CCS as you know produces a very high impedance. Thus for pentodes you usually need a rasistive load, comparably low to the internal impedance of the pentode if linearity is desired.

The reason i ask is that I am looking at another 300B circuit and it uses tons of CCS

But not any Pentodes.

and I think CCS can provide additional linearity on triode, but then why not pentode too?

Because that is how pentodes work.

So, how about replacing the 26 with 310A supplied with 2ma@190V?

The 310A wired as triode? Sure. But what for?

Furthermore, 300B is run at 615V.

No, it isn't, Gary runs the 300B at 335V.

If you lack sufficient electronic knowledge to analyse and modify existing circuits in a sensible way, best stick to building proven, existing circuits or start studying up on electronics.

Sayonara

 

[powertriode]

I continue to read everyone's postings with great interest. Thanks to everyone who replys here.

I have found another WE91 clone, this time the NFB of the original has been kept (but switchable)
The builder has included some test results too.

http://www2u.biglobe.ne.jp/~tossie/300B-E.html

As for CCS, and triode drivers etc. I feel that by doing this you will sway from the WE design which defies the purpose of building a WE91 clone in the first place.

I am not a big fan of silicon going anywher near the signal path in tube amps, I feel a WE clone with added silicone implants would be sacrilige!!!

I will be placing the order with Partridge very soon for the OPTX.
The TK4519 is unshrouded, whereas the TH4663/2 is exactly the same but cased, and this is what I will be buying.

The total cost for them is just over £500 (UK)...just work that out in USdollars!!!!!!!
But still cheaper then Tango (if you can still get them) or Audio Note.

I would certainly like to have some 310's off Frank, how much are you asking?

All the best.

 

[ThorstenL]

Konnichiwa,

I have found another WE91 clone, this time the NFB of the original has been kept (but switchable)
The builder has included some test results too.

http://www2u.biglobe.ne.jp/~tossie/300B-E.html

I dislike Feedback from the OPT secondary. Hence in my case the takeoff from the Anode of the 300B (just as in the original 91).

If you want the option to switch of NFB simply install a Switch that connects the 47k Resistor from the 300B Anode to the 310A Cathode to either Anode of 300B or +B through a resistor of appx 1k5.

Sayonara

 

[fdegrove]

Hi,

Hence in my case the takeoff from the Anode of the 300B (just as in the original 91).

Which is something other SE builders could try as well once they fall out of love with the tons of second harmonics distortion from the beloved SE ampies....

I would certainly like to have some 310's off Frank, how much are you asking?

If you don't mind, send me an e-mail through the forum.

Cheers,