Matching Mosfet already in Amp

[toufu]

Hi guys, I built a new Aleph 30 without matching the MOSFET's, can just I measure Vgs with the amp on and see how closely they are matched?

 

[Loudthud]

That would give you a pretty good idea how close they are matched, but you would be assuming they are all conducting the same current. That also depends on how close the source resistors are matched. Not the best way, but you can tell if there is a gross mismatch causing one to conduct perhaps 5-10% more than the others.

 

[toufu]

What about the differential pair? Would it tell me anything if I measured their vgs?

 

[wayne]

Measure across the source resistors.