PI adjustment PI - exists in other amps ?

[jazzyjoepass]

Can anyone tell me more about the PI adjustment pot? When did it start showing up on his amps? I only know of the Ampeg SVT having a PI pot. Can anyone tell me of any other amps that has this besides the Ampeg SVT?

[talbany]

The PI balance control was a practice used mostly in HIfi amplifiers to control harmonic distortion products or THD..Some engineers looked at it as a kind of harmonic controller since balanced topologies don't generate much if any even harmonic distortion product, so there's no 2nd harmonic, Slight AC imbalance in the push-pull output stage means you get a 2nd harmonic distortion product that dominates over the 3rd which is arguably more desirable in the output section of a HiFi amplifier..Don't ask how this all relates to guitar amplifiers..
Do a search.. Been discussed to death here..

[jazzyjoepass]

Thanks Talbany. I've read some of the discussions here on PI. But what I want to find out is how many amp makers (limit this to guitar amps) had actually thought of putting in a PI adjustment besides Dumble and the Ampeg designers. I'm sure Dumble took a lesson from the Ampeg designers, because he mentioned about them.

[talbany]

Thanks Talbany. I've read some of the discussions here on PI. But what I want to find out is how many amp makers (limit this to guitar amps) had actually thought of putting in a PI adjustment besides Dumble and the Ampeg designers.

AFAIK..Only Dumble and Ampeg..You will more than likely see them in many other amps presently and in the future


Tony

[Mark]

https://tubeamparchive.com/viewtopic.ph ... hlight=amp

[pula58]

Funny, I would have thought that even harmonics would sound good to our ears since the sound is thickened by adding a tone an octave up. Of course, I coiuld be way wrong on this....