Need help solving hum problem


This one really has me stumped....

The system:
Sony SCD-777ES
analog out into Placette Active Line Stage
digital out into Dodson DAC into Placette
Turntable also into Placette
Placette into CJ11A
ALL front end components plugged into Shunyata Hydra PLC

I get constant, low-volume hum when the Placette is switched to either the Dodson OR the Sony analog out, but not when switched to vinyl or any unused input.

The problem is cured when the Dodson is plugged into another outlet (same circuit). Why would the Dodson contaminate the system at all, and (this is the kicker) for two of the sources (itself and the Sony analog out) but not for the phono?

Any ideas? thanks. --dan
Ag insider logo xs@2xdrubin
I don't know what to tell you but i can relate. Have had similar problems with a DAC and specific preamp. Out of curiosity, is the Dodson an upsampler ? Sean
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Well from experience in hooking up litterally hundreds of sytems over years, I can get rid of pretty much any hum from tinkering a bit I suppose. Usually you should first try using a cheeter plug on one of your 3 prong plugs, either on the preamp or amp first.(they'll all still be grounded through connection to one another). Usually, this solves the problem of blatent hum off the bat. Sometimes interconnects or speaker wires are running next to power cords too closely for stretch, and can have hum in the wires that way, but usually not. I have run speaker wires next to high voltage cables with loud buzzing and humming, that's to be considered.
I once hooked up a really really long pair of Interconnects down 2 sides of the room, running along the same path in a wall with some power cords, and it buzzed like crazy.
Anway, hope that gives some food for thought. But I think you might try the ground cheater plug thing first. That usually works. Then, you can try moving your interconnects around, while your system is playing, and see if it's a problem. You might find that if you get the interconnects to lay in a certain way, you'll virtually eliminate hum sometimes.
Good luck
Thank you. I had tried a cheater on both the DAC and the preamp, with no success. I will try it on the amp, but as I said, the hum goes away if the amp and DAC share the same wall outlet. Based on the results of my various troubleshooting attempts, I don't think that the location or proximity of components and cables is the issue in this case, but I do appreciate that those can be factors in system noise.
I have tried EVERYTHING known to man to minimize the hum that i'm experiencing. I'm wondering if it doesn't have to do with how these designers are are using the upsampling devices and trying to keep circuitry to a minimum ???

I recently did a "tweak" that did help this out a bit while making other noticeable improvements though. Since this applies to and can benefit ALL systems, i don't want to "pigeon hole" it to this thread. Look for a new thread on the subject in the next 24 hours. Sean
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