I hooked up the MKIII to my scope and test load. The input consisted of my generator through a volume pot into the input jack. I turned on the amp and let the tubes warm up a few minutes, then I adjust the bias slowly up to 1.4V. This setup is NOT using the balance pot and a single 10 ohm resistor for both tubes like the original. With the scope in the 20mV per division (P-P) I get about 18 mV wide band noise. The scope can not hone in on one frequency, when I shift the time base to look at the higher frequencies, the scope starts to pick out 50kHz through 80kHz noise. I installed an input jumper on the RCA jack and hooked up the amp to a speaker. I powered on and let the amp sit a few minutes to warm up and I verified the bias was 1.4V and I hear nothing at the speaker. I put my ear up to it and its pretty quiet. I took the cover off of the speaker to feel the woofer and there is no movement. I checked my connections to make sure everything was hooked up properly and it was. When I turned off the amp I heard a small pop out of the speaker so it was hooked up correctly. My question is, should I worry about this high frequency noise if it is inaudible? Is there anything you suggest I try short of desoldering the driver or power supply board? Thanks.
BTW this unit has the Bal omitted and is using the C. Chong power supply PCB.