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dolhastelian 18th June 2010 08:07 AM

MOSFET amplifier schematic and PCB needed
Hello everybody,
I'm quite new to this forum.
I have built some years ago an amplifier that hasn't gave me any listening satisfaction. It was built around TDA 7250 + Darlington transistors(does not work well, the transistors are very hot even without any input signal, or at low level).

I want to replace the power stage with a discrete MOSFET amplifier.

I have a power supply of +/- 35V available (toroidal transformer 500W, bridge, filter capacitors: 2x10000 uF).

I saw a lot of threads on discrete amplifiers.

Could someone suggest me a good amplifier (60-100W) with good performance (very low THD: < 0.001) that was built already by someone and eventually has PCB?

Thanks to all !

AndrewT 18th June 2010 09:50 AM

try ESP

riktw 18th June 2010 09:53 AM


look at this amp:
60-80W Power Amplifier
you can buy the PCB's on the website, it performs good and dozens of people already made that design.
and with PCB's it easy to build :)

smartx21 18th June 2010 10:25 AM

Another configuration
2 Attachment(s)
What about changing the output transistors with a different configuration, without darlingtons?
As stated in the original source, "Q1~Q4 is driver transistor to drive Q5~Q8, a SANKEN transistor. Power supply is 40V, and will give 100W power".
I think you can use your supply without changes.
Just tell us what happened afterwards.

Bill Fuss 18th June 2010 11:35 AM


Originally Posted by AndrewT (
try ESP

I built the P101 a couple yrs ago. It's a very competent amp and easy to scale for any power you wish. 35v rails would be fine.

dolhastelian 18th June 2010 11:52 AM

I found Symasym project on the web.

Has anyone built this amp?

Are the specifications real?

I would like to built it. Any comments?

Thank you!

juma 18th June 2010 01:39 PM

There are many threads here about SymAsym, a lot of guys built it, and yes, it's a great amp.

dolhastelian 18th June 2010 03:24 PM

Thank for the encouragement.

To everybody:
Please reply if you built Symasym.

Can I start to build it without any modifications, only using the information on the project site?

Which version to build? 5_2 or 5_3 ? THD for 5_3 is better, they say, is it?

Is the PCB ok?

stoN_Cold 18th June 2010 04:14 PM

Simple & cheap

Regards zeoN_Rider

AndrewT 18th June 2010 04:21 PM

the Symasym is not MosFet.

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