My Mark IIB squeals when the drive is past 7...Help?????

[24loar]

Whenever I turn the drive past 7 the amp squeals horribly. happens on both of my main guitars.....any help or ideas are much appreciated.

tubes are new ( in fact have been swapped with other tubes just to be sure )

Thanks!!!!

 

[Tuna141]

I suggest you try using lower gain 12ax7 or some 12AT-7 preamp tubes. It's either that or your guitar pickups are not potted sufficiently.

 

[MusicManJP6]

depending on how loud you play, if the midgain switch is engaged, it can contribute to added squeal. Seems like it would be something with the amp if two different guitars do it. Unless they are the same pups in both and they happen to be microphonic...

 

[gonzo]

agreed, the only time i've had this effect, was playing at volume, with microphonic pickups.

 

[darkbluemurder]

Whenever I turn the drive past 7 the amp squeals horribly. happens on both of my main guitars.....any help or ideas are much appreciated.

tubes are new ( in fact have been swapped with other tubes just to be sure )

Thanks!!!!

Does it also do this when you turn down the guitar volume? If so the fault is with the amp, not the guitar(s). If ithe ampt does this now and did not do it before then I would try to replace the V1 preamp tube for one that is known to be non-microphonic.

If it does not do this with the guitar volume down, then turn up the gain just to the point before the squealing starts. Put your pick to the pickup. You should hear a faint dull thump. If you hear a loud metallic click the pickup is microphonic and needs to be potted (which some say changes the sound - I have potted more than a dozen pickups and have not experienced a noticeable change) or changed. Some pickups are not that well suited to loud volume high gain playing.
Good luck!