In this exciting episode the possibility of Intermodulation Distortion Reduction in a Class AB2 amplifier by the Allen Wright method is tested.
The amp output is PP 6V6s driven by a 6BQ7 as cathode followers direct into the 6V6 grids, Refer to the schematic,
The driving signal in 80 Hz mixed with 4.7 KHz at 12 db lower level, The measurements follow the SMPTE method.
In test A the 6V6 cathodes are taken straight to the commons rail with the exception of small resisters to allow current measurements.
At 5 watts the IMD measured 1.87 %.
In test B a 47R resister was inserted into the 6V6 cathodes lead to common. The IMD increased to 4,67 %.
In test C the common resister to the common rail was 23R, And the IMD was 3,48 &.
The Allen Wright method did not improve the IMD in this amplifier. 🙂
The amp output is PP 6V6s driven by a 6BQ7 as cathode followers direct into the 6V6 grids, Refer to the schematic,
The driving signal in 80 Hz mixed with 4.7 KHz at 12 db lower level, The measurements follow the SMPTE method.
In test A the 6V6 cathodes are taken straight to the commons rail with the exception of small resisters to allow current measurements.
At 5 watts the IMD measured 1.87 %.
In test B a 47R resister was inserted into the 6V6 cathodes lead to common. The IMD increased to 4,67 %.
In test C the common resister to the common rail was 23R, And the IMD was 3,48 &.
The Allen Wright method did not improve the IMD in this amplifier. 🙂
Attachments
Thanks @jhstewart9 for your tests!
Could raise the resistor to Kiebert reccomandations improve the results?
1/gm for 6V6 in that configuration should be around 270 Ohm.
Could raise the resistor to Kiebert reccomandations improve the results?
1/gm for 6V6 in that configuration should be around 270 Ohm.
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The schematic attached was a trick negative PS that belongs in another thread.
Did this at 1 AM , guess I was a bit tired. The real PP 6V6 Class AB2 amp here.
Here is a link to another discussion of the distortion reducing circuits from DIY about 15 yrs ago.
https://www.diyaudio.com/community/threads/distortion-neutralizer-for-odd-harmonics.111501/
OK Zintolo, I'll try that later today, The snow is coming down steady now, I'll have to spend some time on the tractor.🙂
Did this at 1 AM , guess I was a bit tired. The real PP 6V6 Class AB2 amp here.
Here is a link to another discussion of the distortion reducing circuits from DIY about 15 yrs ago.
https://www.diyaudio.com/community/threads/distortion-neutralizer-for-odd-harmonics.111501/
OK Zintolo, I'll try that later today, The snow is coming down steady now, I'll have to spend some time on the tractor.🙂
Attachments
So here we are, much later. The amplifier in that test series doesn't really qualify for the Allen Wright test, it isn't cathode biased
So I put the amp back the way it was & its on the shelf. again
There is a PP 6AQ5 amp here I could try, just need some time. Snow gone but there could be a big dump yet.