High Pitched Squeal on Tonelab

[Voxman]

In which case you're simply setting gain levels too high on amp and pedal effect.

[Morty123]

I've had two Tonelab SEs one which had this problem and one which didn't. The problematic one got put in the loft while I used the replacement. On getting it down from the loft after more than a year I tried it with a different power supply and the problem had gone! Go figure guys.....

[gonz58]

I got the high pitch squeal the other night at rehearsal while I was using a high gain setting and the power setting on the AD50 was more than halfway. I traced it back to the cables I was using. The guitar to TL cable was a VOX brand cable and the TL to amp cable was a RAPCO cable. Having no other cables with me I swapped them around and the problem was reduced almost completely.

We did a gig a couple of weeks ago and I had no problems then. However I was using 2 RAPCO cables. Hope this helps.

[Mistybreizh]

Excuse me to reply to that old subject, but I think it's far to be closed. I just purchased a (used)Tonelab SE, that I connected in the external loop on my Marshall JTM60 (all tubes), thinking I still could use the 2 channels of the combo. I had this whistleing sound on almost all model amps, as I used even little saturation. I tried to change the tube, but it was all the same, maybe a little less with a 12AU7 which has less internal gain.
The only solution was to use the tonelab as a preamp, having a linear connection guitar-tonelab-JTM60, without using the "send-return" combo plugs.
As the problem doesnt occur with all simulated amps, I suppose it comes from the principle of "valve reactor" they use in tonelabs. This is still a loop, that means signal phase distortion, and if you combine it with another loops, signal phase may move so the tonelab becomes a frequency generator... And all that disturb regular phase distortion will cause the same : bad tubes, bad connection cables, and what else!