I have 7 devices plugged in, if my preamp (tube based self built) and chip amp (LM3886 self built) are in the "always on" bank I get ground loop hum. I get it if either is in the "always on" bank. If I put them both in the switched bank the ground loop goes away. Changing the way the other 5 devices are plugged in doesn't change the hum.
This started a few weeks ago so something has changed and I wonder if something internal in the Panamax is the issue. It is dead quiet with the amp/preamp in the switched band but I wonder if I should just replace it. I bought it years ago pretty cheap used.
I don't really care much about the filtering I just need a decent strip of outlets. Any recommendations?
This started a few weeks ago so something has changed and I wonder if something internal in the Panamax is the issue. It is dead quiet with the amp/preamp in the switched band but I wonder if I should just replace it. I bought it years ago pretty cheap used.
I don't really care much about the filtering I just need a decent strip of outlets. Any recommendations?
I turned the system on this morning and the hum is back. I unplugged the preamp from the Panamax and plugged it back in to the same outlet after 10 seconds and the hum went away.
You could take the Panamax apart and inspect the wiring (unplugged of course!).
You may also have an intermittent in any of your devices. While you have hum, try moving each power cable one at a time, also each RCA signal cable. You want to have more clues as to what you problem really is.
You may also have an intermittent in any of your devices. While you have hum, try moving each power cable one at a time, also each RCA signal cable. You want to have more clues as to what you problem really is.
Antech
I already did all that. With no rca cables connected and all other devices unplugged the hum was there. Plugging the preamp directly to the wall stopped the hum also.
I already did all that. With no rca cables connected and all other devices unplugged the hum was there. Plugging the preamp directly to the wall stopped the hum also.
Okay, if you have an amplifier humming without an input, shorted jacks, the fault is in that unit.
Unless, of course, the voltage out of the Panamax unit is so low that the preamp's power supply drops out of regulation. Should be measurable.
Absolutely true. However that would be a serious failure in the Panamax which has already been checked. His issue is on the non-switched outputs, so for a voltage drop you'd probably see an overheated connection, probably with a lot of electrical noise.
Note that for the high current, non-switched outputs it does not have any series elements with the load.
Note that for the high current, non-switched outputs it does not have any series elements with the load.
I figured it out, it was an issue with the regulated DC preamp filament supply. Variation in the main voltage was causing the input to the regulator drop too low for the the drop out requirement of the LD1084, 1.5v. The input to the LD1084 was varying from 7.5vdc to 7.8vdc, at the lower end it could not produce a stable 6.3vdc and was oscillating. At the preamp output there a signal oscillating from 4mv to 8mv, which was causing the hum.
I lowered the filament to 6.0vdc and it has been dead silent. It is a preamp with two 6N6P tubes, which will be fine with a filament voltage of 6.0.
I would have bet money that this was a ground loop. But after seeing the hum go away after unplugging the preamp then coming back after a few minutes I suspected something internal.
I lowered the filament to 6.0vdc and it has been dead silent. It is a preamp with two 6N6P tubes, which will be fine with a filament voltage of 6.0.
I would have bet money that this was a ground loop. But after seeing the hum go away after unplugging the preamp then coming back after a few minutes I suspected something internal.
