"NewYorkDave" wrote in message
om...
Hi gang. I'm working on the design of an amplifier to be used in a
tube mixing console. (Please, let's ignore for the moment the question
of WHY someone would want to design a tube mixing console in 2003!).

Actually, let's not ignore it - it's often a mistake to give someone
engineering advice if you don't understand why they're trying to do what
they're trying to do. If someone wants a tube mixing console, it is
presumably because they want a certain sound or behavior which they
associate with tube mixing consoles. But obviously, not all tube circuits
sound the same - if they did, you wouldn't be worried about what topology to
choose. So, unless the problem is just that their (your?) studio is too
cold, you really need to know what kind of mixing console they're dreaming
of; find its schematic, or at least its topology; and build that.

But your post suggests that you are attempting to build with the simple goal
of reducing distortion. With due respect to the fact that this is
cross-posted to rec.audio.tubes, I would submit that starting with a tube
design is not the most straightforward way to achieve low distortion, though
it may be a good way to achieve euphonic distortion. There must be some
additional goal, and you need to find it (if you haven't already) or tell us
what it is (if you have).


My distortion analyzer is out of order at the
moment, so I can't look at the distortion products of my breadboarded
circuit.

Do you have a sound card on a computer? Send a sinewave to the circuit,
sample the results, do an FFT.

If not, can you build a reasonably sharp notch filter - even a passive RLC
one, with three components? If so, build one; send a sinewave at the
circuit, adjust the frequency for maximum null, look at the results.

In either case, if you don't have a low-distortion sinewave handy, you won't
get a perfect picture - but it will certainly be good enough to tell you
whether your high-order distortion products are decreasing or increasing.
Just compare with and without the circuit.

But again, low distortion is not necessarily the goal here. We don't know
what the goal is, yet.