Trying to trouble shoot Hum with LP PSU Pre

[K O'Connor]

Hi Jonathan

The PSU-PRE you have is the original version, which for the last few years of its sale included a separate 12V regulator for the heaters. I don't see that in your build and it's the first thing to correct.

The general layout is a bit like a pretzel. Assuming this is the amp with the top cover off AND that the input jack is on the front AND you like the backwards control arrangement, then the innards should be arranged thusly, left to right:
SMPS, PSU-PRE, PA, F-PRE

The controls themselves seem to be in the wrong order even as "backwards" goes, and should be:
AC switch, LED, PA-level, F-PRE Level, Treble, middle, bass, input

The rear connections would be arranged as:
AC input, speaker output

There are two jacks on the rear panel that appear to be uninsulated. What are they?

Star grounding is NOT what you want for audio. TUT3 shows the correct way to wire any amp and is universally applicable regardless of technology.

So, the first thing to do is fix the heater voltage or you'll be burning up tubes. Contact me via email if you need the regulator.