[chazzboggie]

I'm setting up my first system and I'm getting hum through my speakers.

When increase the L and R input levels it gets louder and goes completely away when the input levels are turned all the way down or muted.

I have a Cary V12r, Cary slp98p, moded Stanton st150 turntable from Mapleshade.

The Cary pre amp has a ground connected and all the manual says is its for turntable.

Do I need to ground the turntable and pre amp??

[Domob_in_sf]

I have a Cary SLP-94 and was getting a bad buzz which over time grew unbearable. I tried all manner of fixes until years later I was told to open up the external power supply and look at the capacitor by the power plug. Sure enough, it was leaking and that was the source of the noise. This may not apply at all to your situation, but it is worth considering. Although I don't know if your amp uses electrolytics at that point of the circuit. Good luck!

[JLM]

Eliminate one variable at a time, wall receptacle, swap source, swap pre-amp, swap power amp, swap speakers, etc.

Try to ask from where/who you bought it from for advice.  Call Cary.

[Speedskater]

As 'JLM' wrote, you have to have a troubleshooting plan.  I like to start simple and add units. I unplug everything, then using a ordinary power strip, I start with the amp and speakers. Then I add one source at a time.  Only then do I add things like power conditioners and cables to the outside world.

[avahifi]

Correct, start with the power amplifier connected to the speakers only, no input cables connected to the power amp.  Turn it on, does it hum?  If not, then you have eliminated the amp as the cause of your hum.

Turn amp off.  Connect it to the preamp with no sources at all connected to the preamp.  Turn both on (preamp first, amp last to prevent on thumps).  Does the combination hum? Note that it might be slightly noisier with the volume control completely advanced, especially when switched to the phono inputs.  This is probably normal.  No hum?  Preamp is not the issue.

Now turn everything off and connect the turntable.  It almost always will have a separate ground wire that should be connected to the ground terminal on your preamp.  Try again.  If the hum comes back on the phono inputs only then the connection to the turntable is the issue.  Missing a ground wire?  Try and find out why.  Replace interconnect cables from turntable to preamp if possible.  Check phono cartridge installation.  Are all the tiny wires connecting the cartridge to the headshell done properly?  Let me know what you discover and I will try and help you further.  You can call me at 651-330-9871 for more help if you want.

Frank Van Alstine