[Ian Bell[_2_]]

I have noe obtained a pair of new ElectroHarmonix 6CG7 (marked Made is
Russia 04 04) and tested them in the 5mA mu follower circuit at 20V rms
at 2KHz. The test were done using my new HP3581A WaveMeter which allows
me to see individual harmonics. The results, along with those of th
4-off NOS Matsu****a 6SG7s are as follows:


Tube 2H 3H 4H THD
EH#1 -49dB -76dB -90dB 0.36%
EH#2 -51dB -76dB -90dB 0.29%
Ma#1 -48dB -79dB -90dB 0.41%
Ma#2 -47dB -74dB -90dB 0.45%
Ma#3 -47dB -78dB -90dB 0.45%
Ma#4 -48dB -73dB -90dB 0.41%

In all cases the 3rd harmonic is more than 25dB below the second and the
4th is below the noise floor of the test kit. The EH tubes seems to be
slightly better than the NOS Matsu****a ones which is encouraging.


For reference, the oscillator distortion measures as follows:

2H 3H 4H THD

OSC -88dB -83dB -90dB 0.008%

Cheers

Ian