Transformer based feedback?

bigwill · 4th January 2006, 11:36 AM

First of all I'm going to say that I'm a newbie to electronics, so this could all be a load of rubbish, but I had an idea...

Why not use a transformer to derive the "error signal" between the input and the output of an amp? If you connected the signal to the top of the primary winding of a 1:1 transformer, and the output to the bottom, wouldn't you have an error signal on the secondary which could be used for feedback? Any advantages to doing this or is it stupid?

rozak · 4th January 2006, 12:44 PM

Like this?

bigwill · 4th January 2006, 01:38 PM

That's pretty close to what I thought of, yes

However, I orignally thought of the feedback being applied to the primary instead of the secondary.. Like I said, I'm a newbie so I don't know what the best way of doing it would be

phase_accurate · 4th January 2006, 01:47 PM

Transformer coupled feedback was done in tranformer-coupled transistor push-pull amps for instance. Nowadays these are obsolete.

RF amplifiers is the place where transformer-coupled transistor amps have their merits (and where they are still used nowadays). Some of them actually use transformer-coupled NFB.

Regards

Charles

sreten · 4th January 2006, 03:44 PM

Hi,

the transformer is likely to introduce more distortion than the error
you are trying to correct, very low distortion is not possible with
transformer derived feedback. Quite useful in guitar / bass amplifiers.

sreten.

rozak · 5th January 2006, 07:55 AM

Quote:

Originally posted by bigwill
First of all I'm going to say that I'm a newbie to electronics, so this could all be a load of rubbish, but I had an idea...

Why not use a transformer to derive the "error signal" between the input and the output of an amp?

Any advantages to doing this or is it stupid?

bigwill,
You have very good idea and not stupid.
I built the prototype based on this idea.
Sound was very good!
But there is better topology for trans. coupled amp.

peranders · 5th January 2006, 08:06 AM

Quote:

Originally posted by bigwill

Any advantages to doing this or is it stupid?

I don't say it's stupid more like no insight of the problem you want to solve.

If you don't take into account that the transformer is unlinear (create distortion) and you don't need any galvanic insulation, what other possible advantage would this transformer create? You must always try to state the pros and cons when you have an idea. I admit though that this is hard when you haven't got enough of knowledge.

rozak · 5th January 2006, 09:43 AM

peranders,

1 transistor transformer coupled and loaded VAS sounds better
then "0" distortion OPAMP for me at least.
This is what all diyers looking for?

peranders · 5th January 2006, 09:47 AM

I don't argue with you that you find it better but I still have serious doubts.

Upupa Epops · 5th January 2006, 10:45 AM

Do you like " nice distortion ", Rozak ? But it is your " problem "....

4th January 2006, 11:36 AM	#1
bigwill diyAudio Member Join Date: Dec 2004 Location: UK	Transformer based feedback? First of all I'm going to say that I'm a newbie to electronics, so this could all be a load of rubbish, but I had an idea... Why not use a transformer to derive the "error signal" between the input and the output of an amp? If you connected the signal to the top of the primary winding of a 1:1 transformer, and the output to the bottom, wouldn't you have an error signal on the secondary which could be used for feedback? Any advantages to doing this or is it stupid?

5th January 2006, 09:47 AM	#9
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	I don't argue with you that you find it better but I still have serious doubts. __________________ /Per-Anders (my first name) or P-A as my friends call me

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4th January 2006, 01:38 PM	#3
bigwill diyAudio Member Join Date: Dec 2004 Location: UK	That's pretty close to what I thought of, yes However, I orignally thought of the feedback being applied to the primary instead of the secondary.. Like I said, I'm a newbie so I don't know what the best way of doing it would be

4th January 2006, 01:47 PM	#4
phase_accurate diyAudio Member Join Date: May 2002 Location: Switzerland	Transformer coupled feedback was done in tranformer-coupled transistor push-pull amps for instance. Nowadays these are obsolete. RF amplifiers is the place where transformer-coupled transistor amps have their merits (and where they are still used nowadays). Some of them actually use transformer-coupled NFB. Regards Charles

4th January 2006, 03:44 PM	#5
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, the transformer is likely to introduce more distortion than the error you are trying to correct, very low distortion is not possible with transformer derived feedback. Quite useful in guitar / bass amplifiers. sreten.

5th January 2006, 09:43 AM	#8
rozak diyAudio Member Join Date: Oct 2004	peranders, 1 transistor transformer coupled and loaded VAS sounds better then "0" distortion OPAMP for me at least. This is what all diyers looking for?

5th January 2006, 10:45 AM	#10
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Do you like " nice distortion ", Rozak ? But it is your " problem "....

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