What is the purpose of cap between LTP anodes?

[acheld]

I've being looking at "unofficial" schematics for the BJ IV this summer, interested because of the change in the circuit from fixed to cathode biasing.

As it happens, the biasing scheme looks pretty generic to me.   (The enclosed clip has one glaring error in that C33 is backward, and there may be other errors as well).

Anyway, my question relates to "C14" -- a 47pF cap in between the anodes of the BJ LTP.   This is not a new design feature, and is present in the BJ III.    What is the purpose of this cap?

[SILVERGUN]

Amp Voicing (robrobinette.com)

I was referring to this as a "snubber cap" until I read this from HBP on another site/thread:
"As an aside, it's unfortunate that Robinette chose to call that cap across the phase inverter plates a "snubber". An actual "snubber cap" is a capacitor in series with a resistor, which is placed across a coil or switch to reduce voltage spikes in that coil/switch when current transitions from flowing to stopped."

[sluckey]

That cap will lower high frequency response, mostly stuff you can't even hear. Used to prevent hi-freq oscillations.

[acheld]

stuff you can't even hear

oh that day is long done....

that makes sense.  thanks much. 

[PRR]

Plate impedance of 12AX7 is like 60k. So across two is like 120k.

50pF across 120k is 26kHz.

This is about supersonic whine, not voicing.