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Old 16th February 2013, 12:36 AM   #1501
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Location: Calgary on the Bow
Quote:
Originally Posted by Susan-Parker View Post
I have tried to reply to your PM but it bounced saying your mailbox was full.

Yes, the above works but I am not always able to reply to all emails received immediately due to work, life etc.

Thanks.

Best wishes,
Susan.

P.S. Using transformers as specified, e.g. my own build or Sowter, the amp has a bandwidth of over 200kHz overall.
Thanks so much I apologize for being impatient. I was able to find one response graph for the SE mosfet is there any other bandwidth data which would be useful to supply to the transformer shop or just go with the winding data provided? What does the bottom end response measure like? Is going with power transformers a good option or are the Sowter design the way to go? Thanks for the hand holding. Best regards Moray James.
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Old 16th February 2013, 06:43 AM   #1502
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Default Moray, i have tried to contact you... forum messenger failed

and also have disappeared with my message go you...it vanished.

I tried your direct mail box but also sent me the fail message...maybe you are invaded by a virus doing that.

Try a transformer from Susan Parker directly...ask her the favor to provide you and ship them to you.

This is my suggestion.

regards,

Carlos
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DxS, the best of the best...the cream of the cream, the most magnificent; wide world, ever made, audio amplifier.

Last edited by destroyer X; 16th February 2013 at 06:47 AM.
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Old 19th February 2013, 05:33 PM   #1503
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Default Zeus Transformers

Quote:
Originally Posted by moray james View Post
Thanks so much I apologize for being impatient. I was able to find one response graph for the SE mosfet is there any other bandwidth data which would be useful to supply to the transformer shop or just go with the winding data provided? What does the bottom end response measure like? Is going with power transformers a good option or are the Sowter design the way to go? Thanks for the hand holding. Best regards Moray James.
Do NOT ask a transformer shop to design you something.

The Zeus line and output driver transformers are made by Sowter specifically to my design. The Zeus power stage input transformer was designed with Sowter (two decade ago) specifically to match my amplifier. All three transformers have characteristics quite different from conventional tube designs.

The Zeus specific transformers are all at the bottom of this page:

Replacement transformers for classic valve tube amps.


The suggested Sowter input attenuator is the type 1035 Attenuator with 6 dB Gain and Balance control. 48 dB in 2 dB steps plus 4 x 0.5 dB primary balance taps

TRANSFORMER ATTENUATORS

Please note however that I have not had the opportunity to test my line driver with the 1035 parts since I used the S&B TX102s for my prototype.
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Old 6th April 2013, 11:59 AM   #1504
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Default My Zeus completed

It took a while to complete it but finally it's done. I built all the transformers. I designed and built the interstage transformer as well.
In this version I included the single ended driver (or line stage).
Mosfet used are IXTH20N50D. I used an electronic choke for the tube. The other choke is for the second DC rail for mosfets.
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Old 6th April 2013, 12:30 PM   #1505
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Default Awesome!!!

Quote:
Originally Posted by apelizzo View Post
It took a while to complete it but finally it's done. I built all the transformers. I designed and built the interstage transformer as well.
In this version I included the single ended driver (or line stage).
Mosfet used are IXTH20N50D. I used an electronic choke for the tube. The other choke is for the second DC rail for mosfets.
This is really awesome...

Thank you for posting the pictures. I like the way you have packaged everything together.

Now of course is the $1,000,000 question, how does it sound?

Best wishes,
Susan.
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Old 6th April 2013, 12:46 PM   #1506
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Quote:
Originally Posted by Susan-Parker View Post
This is really awesome...

Thank you for posting the pictures. I like the way you have packaged everything together.

Now of course is the $1,000,000 question, how does it sound?

Best wishes,
Susan.
Well I just finish bench testing it right now and I wanted to post the pictures. It's 23:45 now so I will listen to it tomorrow. I will post the results.
Thanks Susan
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Old 7th April 2013, 11:28 AM   #1507
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Default How does it sound?

First listening test.....
Overall the sound is fantastic.
The first thing I noticed is the high resolution and the extraordinary level of detail (as Susan mentioned sounds nice and crispy), the sound stage and the ability to keep everything in order and clean all the time. It's really a Chinese army parade sort of senario. I've got a single ended tube amp with 12AX7 gain stage and it messes up sometimes when there are several low male voices and several instruments playing at once. But Zeus it's a robust handler of everything that goes to play. Large dynamics.

The frequency response is flat to 50KHz and I think it's limited by the Mosfet's Gate capacitance. The line stage itself with 6c33c is flat to over 200KHz and the interstage up to 90KHz.

I need to pay more attention to the line stage and the AC heater. Any noise generated by the line stage is multiplied by 10 at the power stage. The power stage itself is really quiet.

Amazing!!!

Last edited by apelizzo; 7th April 2013 at 11:32 AM.
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Old 7th April 2013, 01:01 PM   #1508
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Default Wonderful

Hi,

That's wonderful to hear. I can see from the pictures that you have put a huge amount of work into building the system.

Quote:
Originally Posted by apelizzo View Post
First listening test.....
Overall the sound is fantastic.

[snip]

The frequency response is flat to 50KHz and I think it's limited by the Mosfet's Gate capacitance. The line stage itself with 6c33c is flat to over 200KHz and the interstage up to 90KHz.

I need to pay more attention to the line stage and the AC heater. Any noise generated by the line stage is multiplied by 10 at the power stage. The power stage itself is really quiet.

Amazing!!!
When setting up the system as it's defined end to end one can tweak the power stage's Rterm to initially allow a bit of a peak at the HF end from the input transformer which counteracts the mosfet gate capacitance and output transformer's inductance. Needs to be judicious of course, but that does allow an extra bit of extension.

As to heater noise, are you using series or parallel connected heater?

Best wishes,
Susan.
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Old 7th April 2013, 01:18 PM   #1509
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ma'am / sir ...,

do you think stk4050 can drive a 1pc of 18" sub??????

the power of stk 4050 is 200W RMS in the cathalog i dont think so if its real?

i wanted to build a subwoofer amp. that can drive 18" inch sub that its have low cost of building and its have a good quality of sound plz give me any suggestion .

tnx.
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Old 7th April 2013, 01:42 PM   #1510
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Quote:
Originally Posted by Susan-Parker View Post
Hi,

That's wonderful to hear. I can see from the pictures that you have put a huge amount of work into building the system.



When setting up the system as it's defined end to end one can tweak the power stage's Rterm to initially allow a bit of a peak at the HF end from the input transformer which counteracts the mosfet gate capacitance and output transformer's inductance. Needs to be judicious of course, but that does allow an extra bit of extension.

As to heater noise, are you using series or parallel connected heater?

Best wishes,
Susan.
Thanks, yes I've spent lots of time thinking on how to package the system. It is not quite as you designed it: as you see I put line stage and driver in the same box. I had to compromise the design. I understand that the power stage were best left near the speaker and the line stage in the centre next to the source and driving the 600 ohm line to the power stage. Perhaps the next one it will be done differently.

That's good idea. I will tweak Rterm in order to extend the frequent response.

With regards to the heater I think I know what you are going to tell me... Yes the heater is in series because I could grab the 12VAC from the 12+12 transformer (power stage transformer), reducing the current and the section of the interconnecting wire between the cases. I eliminated the noise by adding a 475nF cap between one end of the heater and signal ground. Between signal ground and earth I connected 12Ohm resistor in parallel with 100nF capacitor.
The noise is not completely gone though. I think is the problem with the heaters in series ?
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