toroid Transformer as output Transformer for tube preamp?

tone · 28th January 2003, 04:20 PM

hi all,
has anyone tried before?
can it be done?

thanks for input..

rgds,
tone

dhaen · 28th January 2003, 04:27 PM

Tone,

There are a number of problems:

They cannot accept any DC, so push pull is essential.
There is barely enough inductance.
The interwinding capacitance is not controlled, so different makes with the same ratings will give different results.

I think 316a has done some work with them. Hopefully he'll reply.

Cheers,

tone · 28th January 2003, 04:34 PM

hi dhaen,

can a cap at primary winding do the dc job?

tiroth · 28th January 2003, 04:43 PM

I know some PP amps have been built with Talema toroids. There is a lot of variation in terms of primary inductance; some toroids are quite high.

Bas Horneman · 28th January 2003, 04:59 PM

If u use a parafeed type arrangement you can use toroids..I believe a 50va toroid with a 10:1 stepdown will work..so something like 230v-25volts...
The CCS can be something as simple as a resistor.
Just add a cap in one leg of the primary and voila!

But yes hopefully 316a can shed some more light on the subject.

dhaen · 28th January 2003, 05:01 PM

Tone,

Quote:

can a cap at primary winding do the dc job?

That's a good idea.

Then the primaries could be put in series.

Tiroth,

So desu ka?
I was just wondering whether the smaller ones would have enough inductance. He wouldn't want a 50VA thing in his preamp.

Ja mata.

Of course both ideas depend on the transformer being fed from a sufficiently low source impedance.

I wonder if it worth the trouble. How much does a run - of - the - mill audio stepdown transformer cost in that part of the world?

Kampai,

wiligruen · 28th January 2003, 05:02 PM

Hi,
have a look here

http://home.t-online.de/home/MHuber/pre-5687.htm

Reg.
Wilfried

dhaen · 28th January 2003, 05:06 PM

wiligruen,

That's elegant.

And a tiny transformer too!

Cheers,

tiroth · 28th January 2003, 05:29 PM

dhaen,

Ee. As luck would have it I have a tiny 1.6VA 2:1 toroid (70000 series) and a larger 35VA 27:1 (62000 series) arriving Thursday. I'll measure the primary inductance and report back.

SY · 29th January 2003, 12:06 AM

Tone:

Major dumb question: what are you trying to accomplish? I've always found it useful to define a problem before trying to evaluate solutions.

28th January 2003, 04:20 PM	#1
tone diyAudio Member Join Date: Aug 2002 Location: Malaysia	toroid Transformer as output Transformer for tube preamp? hi all, has anyone tried before? can it be done? thanks for input.. rgds, tone

28th January 2003, 04:34 PM	#3
tone diyAudio Member Join Date: Aug 2002 Location: Malaysia	toroid hi dhaen, can a cap at primary winding do the dc job?

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28th January 2003, 04:27 PM	#2
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	Tone, There are a number of problems: They cannot accept any DC, so push pull is essential. There is barely enough inductance. The interwinding capacitance is not controlled, so different makes with the same ratings will give different results. I think 316a has done some work with them. Hopefully he'll reply. Cheers,

28th January 2003, 04:43 PM	#4
tiroth diyAudio Member Join Date: Dec 2001 Location: Pittsburgh, PA, USA	I know some PP amps have been built with Talema toroids. There is a lot of variation in terms of primary inductance; some toroids are quite high.

28th January 2003, 04:59 PM	#5
Bas Horneman diyAudio Moderator Emeritus Join Date: Apr 2002 Location: The Netherlands Blog Entries: 18	If u use a parafeed type arrangement you can use toroids..I believe a 50va toroid with a 10:1 stepdown will work..so something like 230v-25volts... The CCS can be something as simple as a resistor. Just add a cap in one leg of the primary and voila! But yes hopefully 316a can shed some more light on the subject.

28th January 2003, 05:02 PM	#7
wiligruen diyAudio Member Join Date: Oct 2002 Location: Munich, Germany	Hi, have a look here http://home.t-online.de/home/MHuber/pre-5687.htm Reg. Wilfried

28th January 2003, 05:06 PM	#8
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	wiligruen, That's elegant. And a tiny transformer too! Cheers,

28th January 2003, 05:29 PM	#9
tiroth diyAudio Member Join Date: Dec 2001 Location: Pittsburgh, PA, USA	dhaen, Ee. As luck would have it I have a tiny 1.6VA 2:1 toroid (70000 series) and a larger 35VA 27:1 (62000 series) arriving Thursday. I'll measure the primary inductance and report back.

29th January 2003, 12:06 AM	#10
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Tone: Major dumb question: what are you trying to accomplish? I've always found it useful to define a problem before trying to evaluate solutions.

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