[amb]

Quote:

Originally Posted by drewd Walt Jung's feedback system uses very high amounts of local feedback and just a bit of global feedback.

While this is a true statement, keep in mind that the "local feedback" (a la inner loop) in question here is around an op amp which contains multiple stages, and has a large amount of open loop gain to begin with, so this feedback is not as "local" as the term sometimes implies. In an all-discrete amp, "local" feedback is within the individual stages. In an opamp + buffer design with Jung multiloop, the inner loop is actually quite "global" in scope, excepting only the output buffer.

Just thought I'd mention this in case it's not obvious to some readers.

 

[drewd]

Quote:

Originally Posted by amb While this is a true statement, keep in mind that the "local feedback" (a la inner loop) in question here is around an op amp which contains multiple stages, and has a large amount of open loop gain to begin with, so this feedback is not as "local" as the term sometimes implies. In an all-discrete amp, "local" feedback is within the individual stages. In an opamp + buffer design with Jung multiloop, the inner loop is actually quite "global" in scope, excepting only the output buffer.

Thanks, amb, that's an excellent point to make. Maybe I was a little too condensed. In the case of an opamp-based amplifier, it would probably be more accurate to talk about inner and outer loops as somewhat analogous to local and global, even though it's kind of a tortured analogy. And if anyone knows how to torture an analogy, it's me!

-Drew

 

[gaboo]

Shock, horror, no feedback loops at all.

 

[gaboo]

Quote:

Originally Posted by rickcr42 If you like the sonic qualities of your preamp you can add a unity gain high current output buffer to the line out using the gain of the preamp and the muscle of the buffer to drive cans.This "follower" does not even need to have a volume control,it is provided by the preamp.But what you WILL need is some method of switching the preamp output between buffer and speaker amp or you will need to turn of the amp every time you listen to headhones and unplug your headphones when listening to speakers.A simple A/B dpdt switch is fine

I think I'm on the right track: (1) digital volume control is on the source anyway, so I wasn't planning adding one to the amp, (2) this source (soundcard) is dedicated to headphones, as I'm not allowed to use speakers in the office.

Quote:

if you are using the record out for your headphone amp or you use a passive line stage you are most often better off with a full headphone amp which includes a volume control

I think it doesn't apply to my case...

Quote:

But there are no definitive answers that cover all possible systems and combinations so the above is just a general guideline

Thanks rickr42!!! I'm already overwhelmed.