Simple Symetrical Amplifier

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:)
 

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Very clever circuit; current driven front end with current feedback, most ingenious...

Where did you find it, or is it original?

The zeners are a voltage supply for T1/T2 which act as voltage driven CCSs. The current they create is passed via cascode transistors BF471/472 and 1K resistors to rail to control the gates of the common source output devices.

Voltage feedback from the outputs is passed via direct coupled 1K/100R gain set to modify the current drive to ensure linearity.

Circuit would be very fast but I think the 1K/107 cap is a form of compensation....

Only down side is common source outputs. They tend to complain with reactive loads, and quiescent can be erratic.

Neat!

Hugh
 
Thanks Hugh, it is purely my idea. :)

I like to play with circuits combinations and copying others simply not pleasures my intellect.

Of course any part of the circuit can be upgraded, for instance 1k resistors from +/- 15V can be exchanged with CS, ...

Mosfets can also act like drivers, just simply add EF BJT's for an output stage but than is not that simple amp anymore. ;)
 
Hi Andrej, interesting circuit (as always) :up:

Maybe it will be easier to comprehend when drawn this way:

Thanks juma :)

Well I just barely made this amp in p2p in the air, powered it up and plays music very, very good. What I noticed compared to other amps done is that is amazingly quiet. It doesn't have any noise noticable 10 mm from tweeter cone. Maybe if someone sym this circuit, some interesting data would come out. I know it won't be the best regarding output impedance, THD, IMD, but noise floor, frequency response and phase shift would be very good.;)
 
Very interesting indeed, but most of all very simple and quick to built, good job.

I was looking for a simple low power and not very expensive schematic to built an small amp and i think i have just found it, many thanks @Lazy Cat. I presume the fets can be many tipes, nut just the ones in youre desighn, as long as they present similar specifications, all should be good wright?
 
Correct me if i'm wrong but i think we are not always looking for perfection when building an amp, sometimes we need a simple low cost low power amp and this one looks just fine i think ;)

I agree completely. But my intention and priority is always sound quality and musicality (enjoyment factor at listening), since that is hardly achievable from complex designes. I stoped built complicated ones cause complexity/musicality factor raise exponentialy. ;)
 
This looks quite interesting and indeed, very simple. What's the power ? And could someone post a schematic for the power supply (for a beginner such as I :) ).

Well i presume the power would be something like 30 or 40W on a 4Ohm load, but that is just an asuption, if i'm wrong than i apologise and ask to be corrected.

As for the power supply, well it would have to be something like this:
An externally hosted image should be here but it was not working when we last tested it.


The filter caps should be arround 10.000u at the proper voltage rating, you could add 2 power resistor in paralel with the caps for discharge purpose, as well as 2 ceramic or poliester 100n capacitors in paralel as well with the big ones, to compensate for high frequencyes.
 
@Dmeister

If we asume that +/- 35 V rails potential is stable (maybe even regulated) than we could easily achieve 50 Wrms/8 ohm (3,53 Ap) or even 75 Wrms/4 ohm (6,12 Ap). I would also recommend to set high quiescent current, at least 200 mA through output mosfets.
 
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