You are sure? It seems you have a ground loop so please inspect the device very carefully. Only the casing/chassis should be connected to PE directly.
is it possible that the toroïdal transformer are radiating in the tube?
audio note use metallic tube shield in there preamp...
audio note use metallic tube shield in there preamp...
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je remarque ici que les heathers at 12.6 volt dc are floating (not on the ground plane of the pcb) (may be for ac heathers)
where the B+ is on the same ground of the pcb...
where the B+ is on the same ground of the pcb...
by the way the ground lift has no impact on the hum
except if i connect the box with a 2 prong cable - lifting make a hum with a buzz
except if i connect the box with a 2 prong cable - lifting make a hum with a buzz
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that's after i touch the top of the capacitor
post rectification (heater voltage) with my hand grounded to the enclosure
top part of the cap is bare metal
post rectification (heater voltage) with my hand grounded to the enclosure
top part of the cap is bare metal
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since when is the capacitor enclosure is conductive of ground
this is getting out of my pay grade...
voodoo electronic
this is getting out of my pay grade...
voodoo electronic
I change that board to some lm317 supply (heaters) and i connected the dc ground to the case, et voila:
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so i guess no floating ground (supply for heaters) on single ended phono preamp...
now that it works ok i have to find a way to bring the noise floor better than -110 db
a plus tard with more finding.
now that it works ok i have to find a way to bring the noise floor better than -110 db
a plus tard with more finding.
