@6A3sUMMER - you may already know the trick, but who knows ?
Just put a set of drilled 4mm-thick grommets to isolate the power transformer laminations from the chassis. This was the same problem on most of the 75-80s VOX AC30 (labelled a VOX product), despite that the power and the output transformers were placed at each side of the chassis. The insulation grommets (drilled tap flaps are perfect for this) solves elegantly the issue...
T
There are different kinds of steel chassis.
Most regular steel are magnetic.
Some stainless steel are non-magnetic.
I had a Chinese stainless steel chassis that was slightly magnetic.
I have a very magnetic steel chassis (I am stuck with that, or start over. Un-wire, cut, drill, etc.).
I use Brass screws and aluminum 1/4 inch spacers to mount the choke, and output transformer.
Unfortunately, I can not replace the steel screws on the power transformer, but at least I use the 1/4 inch aluminum spacer.
Your Mileage May Vary.
Most of my listening is Near-Field (about 2-1/2 feet from the speaker).
Most regular steel are magnetic.
Some stainless steel are non-magnetic.
I had a Chinese stainless steel chassis that was slightly magnetic.
I have a very magnetic steel chassis (I am stuck with that, or start over. Un-wire, cut, drill, etc.).
I use Brass screws and aluminum 1/4 inch spacers to mount the choke, and output transformer.
Unfortunately, I can not replace the steel screws on the power transformer, but at least I use the 1/4 inch aluminum spacer.
Your Mileage May Vary.
Most of my listening is Near-Field (about 2-1/2 feet from the speaker).
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No, Mr Jones also strongly recommends Al when Building Valve Amplifiers. But he probably says it Al-Ewe-MIN-ium. But those little Hammond boxes are just so cheap n easy.
I should explain about the 50k potentiometer of my balanced amplifier:
The 50k Potentiometer (connected as a rheostat) is the Volume Control.
The 7 resistors from the XLR connector to the 2 input triode's grids is a Shunt Volume Control.
With perfectly matched fixed resistors, the volume control tracking is always perfectly balanced.
The 50k potentiometer, who cares?, it has nothing to do with balance (the balance from XLR to the 2 grids is Intrinsic).
From the XLR connector, we have:
2 Rg resistors to return the grids to ground if the signal source does not do that; 2 Series resistors as part of the shunt attenuator volume control; 50k shunt volume control rheostat; and 2 grid stopper resistors. Again, 7 resistors, but only 3 resistors form the Shunt Attenuated Volume Control.
With the 50k turned to 50k, the shunt volume control looses about 3dB, versus the voltage at the XLR (perfectly acceptable, because XLR differential signal is 6 dB more than a single ended RCA connector signal).
The 50k Potentiometer (connected as a rheostat) is the Volume Control.
The 7 resistors from the XLR connector to the 2 input triode's grids is a Shunt Volume Control.
With perfectly matched fixed resistors, the volume control tracking is always perfectly balanced.
The 50k potentiometer, who cares?, it has nothing to do with balance (the balance from XLR to the 2 grids is Intrinsic).
From the XLR connector, we have:
2 Rg resistors to return the grids to ground if the signal source does not do that; 2 Series resistors as part of the shunt attenuator volume control; 50k shunt volume control rheostat; and 2 grid stopper resistors. Again, 7 resistors, but only 3 resistors form the Shunt Attenuated Volume Control.
With the 50k turned to 50k, the shunt volume control looses about 3dB, versus the voltage at the XLR (perfectly acceptable, because XLR differential signal is 6 dB more than a single ended RCA connector signal).