Well, here's the initial information. First is the schematic showing the power supply.
Attachment:
schematic.jpg
At low current, tube rectified supplies can be extremely quiet with only simple filtering. Design point on this one is -110dBv ripple at 258v and 1.8 mA. We'll have to see how close it comes in the build. You'll also notice a ground lift switch. This is necessary because I have the metal chassis grounded to the mains safety ground. When using the preamp with a grounded amp, I'll lift the ground and let the preamp signal ground reference to the amp inputs. This eliminates the mains panel ground loop.
And here is how it looks.
Attachment:
Assembled.jpg
Attachment:
top_view.jpg
No fancy wood chassis this time. It's the purely industrial look for this one. I brought everything out through the top plate to simplify wiring. And here is the underside showing the interior layout and tie points.
Attachment:
Underside.jpg
No wiring yet but the build should go quickly. I do have to fabricate one metal plate that will slide into the slots in the Pomona case between the PS section and the amp section. The final filter cap is just on the amp side of the divider. This is to protect the final HV filtering from HV AC fields in this small chassis.
One other note. Pomona uses the absolute worst aluminum alloy for the top plate with which I have ever worked. It is soft and gummy and doesn't machine worth squat. I almost made an entirely new top plate out of 6061 T6. I will probably never buy a Pomona case again. At the prices they charge, they really should be much better quality.
When she's wired and tested I'll post more.
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