My Garrard DD75 has this buzz that is loud enough to be heard over the signal. This must mean something isn't grounded properly, but I can't figure out what. I've experimented with a few ideas but nothing makes any difference. Also, there is much more buzz when I disconnect the ground from the amp. And the hum gets a bit quieter when I unplug the table. Any ideas? What is the best grounding scheme to use?
Here are a couple pictures.
Here are a couple pictures.
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Make sure that the tone arm is grounded to the black ground wire with an Ohm meter.
It is. Not sure if the tube leading to the tonearm is but I shorted it to ground with an alligator jumper and no change.
Then there is a bad ground connection somewhere. Have you tried different cables, since they unplug from the TT?
With the TT plugged into the preamp, use an Ohm meter to check all the grounding from various points in the TT to the preamp ground.
Don't probe the AC line by mistake, that will destroy your meter.
I've had two of those RCA cables on there, and I've used those cables in lots of other stuff with no issue.
It must be a bad ground connection, just a matter of finding it. Should those metal shields be grounded? Though they don't seem to be anywhere near the signal.
Should the tonarm be grounded through the separate ground with the rest of the metal parts? Or would it be better to ground it through the signal ground to keep it separate from other noise?
My fluke could probably survive probing the line on ohm. No need to try though...
You could try grounding the arm separately, this may change the hum. Make sure that the phono cables fit tightly on the sockets, at both ends.
One thing I would also try is to short the cartridge leads for each channel at the headshell, to see if that eliminates the hum.
Have you check the tonearm wiring continuity, from the headshell to the end of the phono cables?
Think I fixed it. Seems it was the cable!
I also added another internal ground wire grounding a piece of metal that didn't seem to be grounded already.
I also added another internal ground wire grounding a piece of metal that didn't seem to be grounded already.
Seems most of the time I rule out the usual suspects I've missed something.
Guess I won't be buying any more of these cables.
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