[Scott Dorsey]

Sean B wrote:
Thanks for the ideas!

The follower was biased at 9mA, driving about 7 volts peak-to-peak into a lightish 4.7k load. I'm measuring with an m-audio sound card which has second harmonic about 120 dB down at an output around 3V rms @ 1 kHz (sine).

Do you really trust that card that much? I might, if I'd measured it with
accurate enough references, but I wouldn't until I'd done that.

One other thing I wonder about: a lot of components made today have iron in their lead wires, can this cause noticeable distortion compared to all copper?

It can cause measurable distortion if there is considerable change in current
with respect to time. This is an issue for things like power amplifier stages.
There is some discussion of it and some examples with measurements in Doug
Self's book. I am inclined to think this is mostly not an issue but you can
get yourself into situations where it might be.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."