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Advice on Constructing Audio Amplifier

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zsolt1

zsolt1

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hi,
did anyone build the amp below ?
amplificator-mosfet-60w-rms-schema-electronica-654x426.jpg
thanks
 

thanks,
i saw that circuit , the LED scared me away .What if i replace it with diode ?
 

Hi,

I saw LEDs instead of zeners, beause LEDs produce less noise than zeners.

But instead of two silicon diodes. Maybe noise, maybe temperature drift. Each silicon diode makes -2mV/°C, so three make -6mV/°C. Maybe a LED is better.
LEDs have low r (delta_U/delta_I).

Klaus
 

Hi,

It says in the notes: "In the original circuit, a three-diode string was wired in series to R10. Two of these diodes are now replaced by a red LED in order to achieve improved quiescent current stability over a larger temperature range"

- Not sure if the LED isn't for improved stability as I don't know about audio circuits, but I use this constant current source as it proves itself to be 99% stable, and found the explanation made sense:

https://en.wikipedia.org/wiki/Current_source#LED_current_source
 
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    KlausST

    KlausST

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led could be better , until it goes out . I had bad experience with using UI characteristic of leds . That's why i use leds only as signaling devices.
 

i'm not into experimenting , just need to build an amp that works from first time. Any other schematic (already tried out) would be great also.
 

Hi,

what about:

LM3876T
TDA7296
or similar

Klaus
 
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    zsolt1

    zsolt1

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I agree that a modern IC power amplifier will work better than the Mosfet amplifier. R17 ruins the damping factor and makes it sound like a boomy old vacuum tubes amplifier.
 

i'm going to build both :)
I think R17 should have a coil wind on itself , that was usual in discrete component amps ..
 

I'm ready with the discrete components amp . Didn't go for the mosfets , i used the good old 2n3055
View attachment ampdiscrete.pdf
I jammed all in a little aluminium box
Saturday_07_November_2015 03_51_58snap.pngSaturday_07_November_2015 03_53_51snap.png
In order to supply the amp with the +0- 25V from 12V (obviously for car) , i inserted a dc-dc converter
suppl.jpg
Basic circuit of supply is from internet with the modifications depicted in paint .The transformer is actually made from a toroid core found in a pc supply . The primary is 30 turns (already on it ) se sec is 2 x about ~ 40 turns (didn't really count , hate winding transformers )

It works fine , almost to fine for what is intended (in a car ...) so this is a positive experience :thumbsup:
Next week ill try the fancy LM circuit
 
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