If you refer to http://www.tubebooks.org/tubedata/RC16.pdf page 27 you will find the description of the "inverse plate-to-plate feedback".
I've included it in my tube amplifier and tested "by ear" with small amount on NF (very large R), but still combined with my original -6dB GNF network.
Sound is nice, much more clean and detailed, but unfortunately I lost gain and some dynamic as I was expecting.
THD slight increased but sound is better...
Only few people is using the p-p NF, so I'm wondering if it is just because of the gain/dynamic lost or because it is very difficult to tune in order to get real sound improvements?
I've included it in my tube amplifier and tested "by ear" with small amount on NF (very large R), but still combined with my original -6dB GNF network.
Sound is nice, much more clean and detailed, but unfortunately I lost gain and some dynamic as I was expecting.
THD slight increased but sound is better...
Only few people is using the p-p NF, so I'm wondering if it is just because of the gain/dynamic lost or because it is very difficult to tune in order to get real sound improvements?
That points to the driver stage which is not up to the task. THD should be lower.
Anyway you should measure how THD changes with the load (speaker). You can first try with various resistive loads. That is the main reason why this fb should be used. Maybe you see less distortion. Pentodes can give very good distortion figures on fixed load but they are weak on variable loads such as speakers.
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