Need suggestion

tony Ma

2011-02-25 10:06 pm
Dear All,

I am looking to build SS class A amp from what ever left with my B&K ST-140

Here what I got

1. Case 16x13x5.25 inch
2. on the back there is a heat sink size 7.5x4 inch
3. Transformer with secondary wiring 46x2 (I measure it)

and there is writting on the transformer

-904 wattage 300 W

Any suggestions ??? I like to make Amp with heavenly sound.....
Not recommended for class A amplifier.

Why? because Class A passes a lot of continuous current, always.
The necessary current for an 8 ohms load will be very high, pull more power from the PSU than it can deliver.
As Jay said in post #2, class A amplifiers use relatively low +/- rails, to keep power dissipation at bay.
Not the case here.
The original PSU was designed for a class AB2 amplifier, you can't veer away from that, unless you get a 300VA transformer but at a quite lower voltage.
So all you could use is the case and heat sink, mut notmuch more. :(

Personally I would rebuild or clone an ST-140 or build there a standard power amp (your choice) , which is happy with +/-V rails.
AB class, of course.

*If* you insist on a class A amp, fine with me, but pick any suitable schematic (lots of them here) and get a *new* transformer, which is more suitable.
Good luck.