Orange Rockerverb reverb driver oscillation

[Helmholtz]

Could it be that you mixed up drive and recovery tubes at places in your post above? E.g. the recovery tube already should be a 12AX7.
Please clarify.

I didn't expect that it would require that much series resistance with your amp.

Did you try lifting C12 instead? That completely eliminated the problem with my Fender amp. But also lowers rev. drive by maybe 6dB.

It is normal that the grid signal clips when Vpp exceeds twice the cathode voltage.

[htrd]

Could it be that you mixed up drive and recovery tubes at places in your post above? E.g. the recovery tube already should be a 12AX7.
Please clarify.

As I said in the first post, the schematic contains few errors. Driver and recovery stages are both 12AT7, not 12AX7.

Did you try lifting C12 instead?

Not yet, we tried non-invasive methods today. We left lifting C12 and increasing R23 for the backup scenario, if the series resistor wouldn't help. Anyway, it would require raising the gain in the recovery stage.

[Helmholtz]

Ok, then use a 12AX7 for recovery. Should work fine without tweaking.

Otherwise I don't see possibilities to increase recovery gain.

[htrd]

Small update.
Tried 12AU7 in the reverb driver. It works surprisingly well, very little distortion without any resistance in series with the transducer. I ran out of small resistors, will try it later with something around 10-15R to completely eliminate the problem.

[Helmholtz]

12AU7 has less gain than 12AT7.

As the driver stage is a little power amp, I would use a 2W rated resistor.