Tube Amp Schematic

what is causing sqeualing in 12AX7/LM386 hybrid guitar amp?

I recently made a small guitar amp according to this schematic;

http://www.sophtamps.ca/mambo/index.php?option=com_content&task=view&id=28&Itemid=39

however when using the amp whilst the gain is turned on even slightly a high frequency sqeualing occurs, what could it be? is it the tube (its new). or the Wiring; here are some pictures of the amp:

http://aycu21.webshots.com/image/37900/2005056713895841154_rs.jpg

http://aycu20.webshots.com/image/40339/2005064695734689145_rs.jpg

Your preamp is oscillating. Check your wiring very carefully – somewhere you have amplified signal feeding back into the input. Pay special attention to grounding – if something that should be connected to ground is not, that can cause the feedback.

I just took a look at your photo: You have very long leads running around that will cause capacitive coupling between the input and amplified signal. The leads around the 12AXY must be very short (an inch or two) and the input leads to the first stage grid shielded.

Homemade Guitar Electronics 15 watts tube amp