Jib,
The HA--2 is indeed a gem. I had one, upgraded it a bit and built two more insane variants with Pete's guidance and additional help from the DIY community. If you have never taken the cover off the HA-2 you should, taking proper safety precautions, and check on the power supply caps and R1. The power trafo runs hot and the caps are run pretty hard which can lead to premature failure and increased noise.