Split Phase PI vrs Long Tail PI

[sbirkenstock]

Hi everybody,

I wanted to try out a split phase PI in my BF Vibroverb project amp.
Copied it basically from the BF Princeton (AA964, no reverb).
Got way lower in volume, so I put another triode in front of it.
Now it is way louder than the long tail (I read it is twice as loud somewhere, it´s somewere in this area).

Also sounds nice.
What it does though, it takes away the top end sparkle in my amp.
Is this common with this change?
To my knowledge all Orange Amps have split phase, and they don´t have much sparkle, at least compared to an Marshall.

The BF Vibroverb schematics show two 100K resistors in the PI.
Many others have one side at 82K (BF Super Reverb).
So they are offset a bit.
I added different resistors to the plate side with the split load to offset it as well.
Going from 56K to 56K + 27K.
(Also tried +10K and +37k)
That brings the sparkle back!
The bass get´s a lot "dryer", sounds great with my strat.
But I also get early distortion, especially at the treble side, that does not sound too great.
Any hints on that?

I also found out, that with all preamp tubes the voltage at the plate, no signal applied, fluxiates by about .1 volt.
On my split load phase inverter, it does go up and down by about 1 volt.
Any hints here?

Any experience/idea what kind of tube to use here? 12ax7 or 12at7?

Thanks a lot!
Stephan