loud sqeal noise

[pancho510]

I built a Double Six amp its a cool amp I like it. I didn't buy a kit from Ampmaker but I built it per their schematic I did change R17 res from 220k to 67k too lower the gain and I used edcor tranies.
In the lower voltage setting there is no squealing at all but at the other 2 voltage settings I need to turn down my volume knob on the guitar or gain on amp or both so it doesn't squeal. Is there a general problem why amps will squeal when pushed.

[Tillydog]

Did you follow the ampamker layout?

You could try temporarily disconnecting the negative feedback connection from the 4 ohm tap to R14 to to see if the NFB is causing the problem.

[joshdfrazier]

This happens alot when the OT secondary winding is not referenced to DC ground/common on the chassis. If your 1/4" jack is mounted on your chassis, just connect the - terminal to the sleeve of the jack. Just make sure to follow a known good grounding scheme, or use star grounding.