Problems adding buffer to Boss HM-2 clone - please help!

[themachinerages]

Hey all,

I have a high-pitch squeal / oscillation on my Boss HM-2 clone on the last 25% of the volume pot sweep.

http://2.bp.blogspot.com/-dMh-yFDJ23I/U4PQZhso-SI/AAAAAAAAHfI/PayAmAfwZ90/s1600/Boss+Heavy+Metal+HM2+with+mids+control.png

Thanks to a suggestion from Reddit, I tested with a buffer before the pedal and the squeal disappeared. I had the buffer circuit attached into my test box and sent the output into the HM-2 clone. The two were daisy chained via the same power supply and connected via patch cable.

Next I tried adding the buffer to the pedal. I swapped the input of the HM-2 on the 3PDT with the input to the buffer. I took the output of the buffer and soldered to the input of the HM-2 circuit. I soldered the 9V and ground for the buffer to the DC jack.

But the squeal is still there! I removed the buffer from the circuit and back to the test box and the squeal disappears again.

I am using the TagboardEffects off-board wiring style if that could affect anything - http://1.bp.blogspot.com/-k5Sh68yVU18/TzGRFKbiALI/AAAAAAAAAlk/CbfaaduUjYQ/s1600/%21Offboard+wiring.png

Any help is greatly appreciated! I am so confused. Why would wiring it in the enclosure be any different than running them in series with the buffer in my test box?