20W speaker amplifier

[Simon123]

Hello!

I kinda designed 20W speaker amp and would like, that somewhone would check it and point out the errors.
Base current of TR1=350uA, Ic=35mA
IB TR2= 35mA, Ic=1,78A
2n3055 collector resistor is to low value for power, il change that.
I realy dont care about current consumption, cuz i have 10A transformer and that shouldnt be big deal.
Is 2N3055 good for audio?
Is this designed properly for class A amplifier or AB, dont care ?

Thanks!

[T3sl4co1l]

The first stage looks right, the second stage is suicide biased.  You cannot rely on hFE, it is a secondary parameter and varies by about 250% between different pieces of the same transistor type, different brands, and over temperature and operating current.

There are better ways to heat ones' home,

Tim

[Simon123]

Should i make it voltage divider then?

[peter.mitchell]

Is this project for learning or just to make a practical quick widget? if it's to make a quick practical widget, for the price of 3x 2n3055s you can buy a TDA7292 and you're almost done.

[wiss]

Should i make it voltage divider then?

If you insist on going discrete, yes!
And an emitter-resistor on the power-transistor to somewhat control the gain and bias-current.
This will be a very good way to heat your home and spend money on heatsinks.

[Simon123]

Its kinda for learning, so i can understand all on the circuit.
To understand some pushpull ic is more dificult if i dont understand this.
As heatsink il proably just use 3mm piece of aluminium.

Thanks for replying.

[madires]

I realy dont care about current consumption, cuz i have 10A transformer and that shouldnt be big deal.

One or two secondary taps? If it got two go for the classic push-pull approach. BTW, to calculate a proper input coupling cap please use f = 1 / (2 * pi * R * C). That's the lower frequency limit at -3dB (coupling cap plus input impedance creates a RC filter).

[wiss]

Its kinda for learning, so i can understand all on the circuit.
To understand some pushpull ic is more dificult if i dont understand this.

Sure, go for lower power and it will work

As heatsink il proably just use 3mm piece of aluminium.

a few sqaremeters? 

[Simon123]

OK, il calculate capacitors, this is just some aproximation i think should work.
I only have single sec. tap.
Il use fan for transformer in powerhouse also.