"Phil Allison" wrote in message
...

My ancient Heathkit audio signal generator, which uses 3 tubes and a
light bulb in an oscillator circuit, claims to produce sine waves with a
total harmonic distortion less than 0.1%.

** Err - at what frequency/s ???

Betcha that is true only above 50 Hz and below 20kHz.

I think that's right.

My semi-ancient Hewlett-Packard HP202B oscillator only claims to produce
THD less than 1%.

** The 202B is a very low frequency design - operates down to 0.5 Hz.

If it manages 1% THD at that frequency, using bulbs to stabilize the
level - it is tops.

Would the THD be appreciably lower at the mid audio frequencies?