Power supply for Super Leach amp


2001-12-12 1:45 am
I saw on Leach web page that he recommended al least two 10000microF / 100V per channel. Would it be OK to use four 6800microF / 100V caps per channel? These are high quality caps made by German factory Fischer&Tausche and each has current rating of 6.5A
Transformer is 1500VA toroid with separate secondaries for each channel and the voltage is +/- 85V at maximum current around 6A ( totaly + and - rail together 12A).
For bridge I will use one 400V 35A device per channel.

Am I on the right way to the sound heaven?

The value of smoothing caps are determined by how much ripple you accept.

I think it sounds a little bit too little for a 110-120 V supply. Was the AC voltage 85 V?

The formula is

Vpp = (I*t)/C

t = 10 ms @ 50 Hz
I = the current out

The formula is a simplification.

Notice also: If you have huge smoothing caps you can take out only half of the rated power (in your case only 750 DC-watts! You creates lots of reactive power.

Gut feeling says 22000-47000 µF.
I used a Plitron1500VA transformer with 55000uF of capacitance per rail for a pair of channels on the SuperAmp. Under small impedance loads, the rails dropped from 90V unloaded / idle to about 69.5 with only one channel driving into about 2.75 ohms. When the rail drops like that, it limits the total amount of power. However, under musical conditions this type of output is not typical. The more capacitance the stiffer the rail and the higher the output power CAN be into small loads. I would go with a higher rated voltage cap. 90V rails and 100V caps are not a good mix and just beggin for disaster down the road....but otherwise sounds good.