Common-cathode triode vs source-follower Hexfet. - Page 2

ashok · 17th March 2003, 09:27 AM

Quote:

EI core 96x82x33mm outer dimensions, approx 9 cm sq,

Hi Zelko,
How many turns did you use ? Have you wound any transformers for Tube outputs ( Ultra linear output ?). I want to wind my own transformers and would like to know how you would wind that. Any special way to wind apart from bifilar ?
I have CRGO ( cold rolled grain oriented silicon steel cores).
Thanks.

Circlotron · 17th March 2003, 10:53 AM

How many volts and amps did you run on the IRFP240, and..... what did it sound like???

Zelko · 20th March 2003, 10:52 AM

Hi,

I have made a lot of output transformers in the past 35 years, and I do not like the sound of push-pull pentodes, ultralinear or else. Much unnatural despite good lab testing.
As it is source follower with low impedance, trafo does not need many wire turns and as such the best way is bifilar, i.e. tight coupling and wide freq. response, unfortunate I do not remember how many turns there is. I have made several different trafos and all were good. As it is not critical, I just filled available space with wires.
As for core type I used ordinary mains type core material but You could use anything at hand. Grain oriented will work even better.
Again it is not critical design, nothing like pentode push-pull type trannies, do not worry.

I made only laboratory testing so far and would not know how it sounds. Hope to find out soon.

Power supply was aprox. 20V single.

I hope this was helpfull, best regs.

Circlotron · 21st March 2003, 02:00 AM

If the transformer was from mosfet source to ground and the bottom end of the secondary was grounded and *only* if the transformer has 1:1 turns ratio then you could put a 10uF to 20uF film cap from the top of the primary winding to the top of the secondary winding to make the coupling virtually perfect. some peple may think that is not necessary, but if you are only making one for yourself then every little bit helps toward making it perfect.

Zelko · 22nd March 2003, 08:35 AM

Hi Cyclotron,

Yes, can do, but see what happens with ringing on capacitive load as this was the reason for transformer in the first trials with inductor + capacitor combination!
On the second thought I would suspect complex phase behaviour in this combination...

regards, Zelko,

17th March 2003, 10:53 AM	#12
Circlotron diyAudio Member Join Date: Jun 2002 Location: Melbourne, Australia	How many volts and amps did you run on the IRFP240, and..... what did it sound like??? __________________ Best-ever T/S parameter spreadsheet. http://www.diyaudio.com/forums/multi...tml#post353269

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20th March 2003, 10:52 AM	#13
Zelko diyAudio Member Join Date: Mar 2003 Location: Zagreb	Hi, I have made a lot of output transformers in the past 35 years, and I do not like the sound of push-pull pentodes, ultralinear or else. Much unnatural despite good lab testing. As it is source follower with low impedance, trafo does not need many wire turns and as such the best way is bifilar, i.e. tight coupling and wide freq. response, unfortunate I do not remember how many turns there is. I have made several different trafos and all were good. As it is not critical, I just filled available space with wires. As for core type I used ordinary mains type core material but You could use anything at hand. Grain oriented will work even better. Again it is not critical design, nothing like pentode push-pull type trannies, do not worry. I made only laboratory testing so far and would not know how it sounds. Hope to find out soon. Power supply was aprox. 20V single. I hope this was helpfull, best regs.

22nd March 2003, 08:35 AM	#15
Zelko diyAudio Member Join Date: Mar 2003 Location: Zagreb	Hi Cyclotron, Yes, can do, but see what happens with ringing on capacitive load as this was the reason for transformer in the first trials with inductor + capacitor combination! On the second thought I would suspect complex phase behaviour in this combination... regards, Zelko,

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