AH Pre line stage

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Today is nostalgia day, it seems. Good ol' AH. I'm not sure what he's up to these days, I haven't been in the d.r.m.h newsgroup for ages (I'd have to look for another newsserver, for one).

As mentioned, it's just an opamp with a simple Class A MOSFET source follower (Szekeres style) as a buffer, so that it can be used as a headphone driver as well. It's not terribly efficient power wise, and could be made much better distortion wise by using a simple 1-transistor or LM317-based current sink instead of R43, but it does work. Using it with an OPA134 isn't a bad idea because this one can swing quite close to the rails, and you're losing several volts in the MOSFET.

Typically people prefer AB push-pull buffers for headphone amps, which don't have to run that hot yet can provide output current far above bias current level (which the above cannot, it's strictly Class A). And as long as bias current is high enough to cover usual output currents in Class A (for which it only needs to be half as high as in the single-ended buffer), distortion in that range will be just about entirely be dominated by the opamp as well.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.