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-   -   Tube Hybrid 25W Class-A, Opinions? (http://www.diyaudio.com/forums/tubes-valves/13824-tube-hybrid-25w-class-opinions.html)

Algar_emi 16th April 2003 01:58 AM

Tube Hybrid 25W Class-A, Opinions?
 
I'm considering building this very nice hybrid amp, Class-A 25W:

http://www.diyaudio.de/html/25_25w_hybrid.html

It has balanced inputs, Lundahl input and interstage transformers, Absolutely no capacitor in the signal path
Zero dB feedback and 2-stage current amplification using Hitachi® Mosfets as driver and Sanken® bipolar power transistors.

Any comments on the tube preamp section?
Seems a very nice desing.

Thanks for your comments.

Bye.

Tube_Dude 16th April 2003 02:26 AM

The missing capacitors...
 
Quote:

Absolutely no capacitor in the signal path
Hi Algar_emi !!

Nice project...but i count 4 capacitors in the signal path in each channel...;)

Algar_emi 16th April 2003 02:36 AM

I don't see the caps
 
I checked again but I didn't see any caps. Where do you find them?

Bye.

PassFan 16th April 2003 02:47 AM

It looks involved, expensive and redundant. I'm not trashing it but, why go from tube to mosfet to bipolar. Aren't each one of these kind of a contradiction in sound. I mean if you like the sound of tube's then I could almost see the mosfets, but bipolars don't sound like either one of those. They are unique unto themselves aren't they? I am in no way questioning your taste, merely making some observations and asking some questions.:scratch: Maybe I'm too simple at times. Do you know anyone who has heard it? After all, that's what it's all about.

Tube_Dude 16th April 2003 02:48 AM

Re: I don't see the caps
 
Quote:

Originally posted by Algar_emi
I checked again but I didn't see any caps. Where do you find them?
Only in one channel...and not quoting the plastic bypass

C27-C34-C3-C4....

Bye;)

Tube_Dude 16th April 2003 03:03 AM

The follower of the follower...
 
Quote:

Originally posted by PassFan
It looks involved, expensive and redundant. I'm not trashing it but, why go from tube to mosfet to bipolar. Aren't each one of these kind of a contradiction in sound. I mean if you like the sound of tube's then I could almost see the mosfets, but bipolars don't sound like either one of those.
Questions about sound a part (subjectives) ...the reason why the designer use a bipolar follower after a source follower is for to lower the output impedance..as the amp don't have overall feedback

For instance if the mosfet output impedance is 1 or 2 Ohms...after the bipolar folower this became the (current gain of the transistor times)..less..

Exe. output mosfet impedance mosfet 2 Ohms... current gain of the transistor 50...the output impedance become 2/50=0,04

PassFan 16th April 2003 03:21 AM

Re: The follower of the follower...
 
Quote:

Originally posted by Tube_Dude


Questions about sound a part (subjectives) ...the reason why the designer use a bipolar follower after a source follower is for to lower the output impedance..as the amp don't have overall feedback

For instance if the mosfet output impedance is 1 or 2 Ohms...after the bipolar folower this became the (current gain of the transistor times)..less..

Exe. output mosfet impedance mosfet 2 Ohms... current gain of the transistor 50...the output impedance become 2/50=0,04

Thanks


:)

Algar_emi 16th April 2003 03:29 AM

How does it sound?
 
Yes you are right. It is what i'm trying to find and no answer yet. Please any comment on this kind of hybrid desing will be appreciated.

I expect this desing to sound kind like a pathos hybrid, see http://www.pathosacoustics.com/classiceng.htm

I don't mind a complex project, see my dac: http://www.diyaudio.com/forums/showt...threadid=12464

This kind of coupling transfo are used (I think) inside the Nagra preamp...

Tube_Dude 16th April 2003 04:00 AM

The Pathos...
 
Quote:

I expect this desing to sound kind like a pathos hybrid,
I don't ...as the Pathos doesn't use interstage transformers...so your's will have another "flavour"...

But try your project...and repport!!

cheers ;)

JoeBob 16th April 2003 04:46 AM

I'd say go for it if you're up to the complexity. I use a tube/MOSFET hybrid and I very much enojy it, it's alot simplier (I think the simplier the better, to an extent). So while some may not like hybrids, I can vouch that they can sound great.


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