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Old 4th January 2006, 11:36 AM   #1
bigwill is offline bigwill  United Kingdom
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Lightbulb 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?
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Old 4th January 2006, 12:44 PM   #2
rozak is offline rozak  Israel
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Like this?
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Old 4th January 2006, 01:38 PM   #3
bigwill is offline bigwill  United Kingdom
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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
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Old 4th January 2006, 01:47 PM   #4
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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
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Old 4th January 2006, 03:44 PM   #5
sreten is offline sreten  United Kingdom
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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.
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Old 5th January 2006, 07:55 AM   #6
rozak is offline rozak  Israel
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Default Re: Transformer based feedback?

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.
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Old 5th January 2006, 08:06 AM   #7
Electrons are yellow and more is better!
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Default Re: Transformer based feedback?

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.
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Old 5th January 2006, 09:43 AM   #8
rozak is offline rozak  Israel
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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?
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Old 5th January 2006, 09:47 AM   #9
Electrons are yellow and more is better!
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I don't argue with you that you find it better but I still have serious doubts.
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Old 5th January 2006, 10:45 AM   #10
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Do you like " nice distortion ", Rozak ? But it is your " problem "....
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