My bad! Just a loose connection on the positive rail of the left channel. Weird.
Offsets now perfect ~4mV both channels.
Yes, you can bias as hard as you like. Just change the bias trimmer value for something larger.
It's pointless though - The improvement in performance is naff-all, and all you'll do is heat up the room.
This amplifier, with it's fast high open loop gain, is designed with reasonably low bias, to be one of the more efficient LatFET amplifiers.
A shorted Mica cap? As we used to say "Murphy was an optimist: He thought only things that could fail would fail." We came to understand that things that couldn't possibly fail will also fail! Or as a mentor of mine said "No, you won't see it in the units you build in the lab, you won't see it in a pilot run, but you will probably see it in the first 100K units, and you will certainly see it when you build a million of them!"
https://www.worldradiohistory.com/AUSTRALIA/Australian-Electronics-Monthly.htm
Here's something you're looking for...
Here's something you're looking for...
You can look bob cordell lsk389 desing note for preamp, but lsk389 is not good for this amp, because input capacitance little high and it is mean low slew rate… Lsk489 jfe2140 or sst402 could be nice. Jensen 990c or skulptor sk99 discrete opamp could be nice. also my favorite opa1641-42 or opa1655-56 for simple preamp…But if you have dac thats been vout 2vrms, you do t need to preamp. If your sources have vout 250mv like phone stage you need to preamp…. I started to desing new discrete preamp class a (balance and se input direct input or 8x gain, mc mm phone input.)i can share whrn it finish. Definitely i have started to use cap bank on my amplifier. 5x4700-3300 or 2200uf. Cheaper but super fast and good perfermons with Low esr caps.
