ruffrecords said:
What load did you use when measuring the harmonics?
The 100K anode resistor is rather high. I suspect this plus the 2K2 cathode resistor means the tube is running at quite a low current. This means its output drive capability will be low and its output impedance relatively high both of which will result in higher levels of distortion.
Cheers
Ian
i was using my lynx 10K in 600r out.
yes, higher the input level is higher the distortion, but very rich on 2nd harmonics.
i tried 47K and lower/higher cathode resistor, but then i am loosing the 2nd harmonics...
3rd harmonic is jumping in quickly.
its kind a sweet spot at the moment for 2nd harmonics, unless i push it really hard.
(i was thinking this as 8 ch mixers ch input, when i mix 8 channels of stems/groups, none of the audio stems/groups would be that high to push the input to distort too much,
but under 1% THD, mainly 2nd harmonics.... )
frequency response is near flat, except there was a bump at 10hz when i measured with 1uf C1 cap.
then changed C1 to 0.22uf, but didnt measure it yet..
edit: when used the second half of tube, then things are more controllable (similar to NYD's design!)
but i like the idea of only one half for simplicity!