Who can explain this Peavey PI?

[leadfootdriver]

I never seen this before. Why not a Long Tailed Pair?

[jazbo8]

It's a cathodyne if you follow the signal path.



Jaz

[es345]

Interesting to see the texture poti:
it allows to drive the PP powerstage unbalanced, that will create even harmonics

Hans- Georg

[leadfootdriver]

Thanks for explaining guys!

As for the sound: how does a LTP compare to the Cathodyne, and vise versa?

At the least, it looks like you get an extra gain stage if you need it. Cool.

[woodyc]

...As for the sound: how does a LTP compare to the Cathodyne, and vise versa?...

I doubt anybody could tell the difference between a cathodyne and a Schmitt in a blind listenting test, but the cathodyne has a lot more even harmonic distortion when pushed.

Its mainly because when the power tubes driven by the cathode side start to clip and their impedance drops, it turns the splitter into a gain stage from the point of view of the plate. But the vice-versa doesn't happen.

For example, here's a pic of the clipped output of a Kalamazoo Reverb 12 splitter, cathode at top, plate at bottom.

[leadfootdriver]

Thanks for that insight!

[jrfrond]

The cathodyne phase splitter is unity gain (input = output), requiring a driver stage before it.

The Schmitt, or Long-Tail Pair, also amplifies in each triode. One triode is configured as typical common-cathode, the other as common-grid.

The Peavey TEXTURE control on the ValveKing introduces asymmetry into the drive circuit. Cathodyne PI's are usually pretty balanced, and this "dirtys" it up somewhat. Asymmetrical clipping sounds more interesting to some ears.