Question about Trainwreck Komet 60 PI Circuit

[PCollen]

The Komet 60 has a 220K resistor following the coupling cap on the V3 plate. Why ? I've never seen a resistor used at this position before. Is it acting as a signal attenuator in concert with the 1M on the input grid of the PI ?

[Blackburn]

Edit: I'm thinking of the wrong one. I was thinking of the 220K like in the Rocket schem for 'blocking distortion'.

[M Fowler]

I'm not sure why it is there and really never thought about it until now?

[roberto]

This acts like a grid stopper to avoid blocking.

[roberto]

This acts like a grid stopper to avoid blocking.

[PCollen]

This acts like a grid stopper to avoid blocking.

Thanks, x2.

[Gaz]

I remember Aiken writing somewhere that the 220K negates the whole purpose of the follower...

[Gaz]

Found it...

The problem is, that cathode follower will never distort in that configuration. It will remain extremely linear throughout it's range. The typical Marshall triode/cathode follower stage distorts the bottom of the waveform because it drives a relatively low impedance, frequency-dependent tonestack (the impedance can go as low as the value of the "slope resistor" for some frequencies if the mid control is zero).

If this one is configured as claimed (I've never seen one in person), it is doing nothing. It isn't even providing a low impedance drive to the PI, because there is a 220K resistor stuck in there, raising the impedance even higher than it would be if there were no cathode-follower at all, so you don't get any extended frequency-response benefit, either. The only slight advantage you might get would be if the output of the cathode follower had to drive a long wire over to the PI. If the 220K resistor was placed over at the PI, you may get a bit less noise/crosstalk pickup because of the low impedance run.

Randall Aiken