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Parasound JC 3+ Phono Preamp Hum

I know hum problems have been discussed ad nauseam on this board, but after trying a few different things, I have been unable to find a solution. I recently purchased a used JC3+ to replace a PS Audio GCPH with Underwood Mods. Although the GCPH had some hum, the volume had to be turned up to past 50% before it was audible.

With the JC3+ I get a low hum at 25% and loud hum at 50% volume. What I am describing is with everything on, no record playing.

The SL1200G TT is grounded to the JC3+. I’ve tried the following: 1. Added a ground wire from the TT to the integrated chassis, a Cayin A-88T Mk II. 2. Changed cables from TT to JC3+. 3. Changed cables from Integrated to JC3+. 4. Plugged JC3+ directly to wall outlet. 5. Changed to AC polarity on the JC3+ via the switch on the back from normal to invert. 6. I’ve tried using no ground wires.

Due to my cabinet configuration, power cables and audio cables run parallel and close to each other. There is no way I can arrange them to be perpendicular to each other.

If I lift the tonearm and let it fall back on the cradle, I can hear the echo or bump through the speakers.

My cartridge is a Hana SL.
Cables: TT to preamp, Silnote Morpheus
preamp to Integrated, Morrow MA4 (and tried AQ King Cobra)

Everything is plugged into a rather inexpensive, basic Belkin PF30 power strip.
I have been considering upgrading to a AQ Niagra 1000. Not sure if that would help with the hum.

The JC3+ is definitely a better sounding preamp than the GCPH . I can’t hear the hum when playing music, but I’m quite disappointed that the JC3+ hums louder than the GCPH.

Again, I know hums have been discussed to death, but any ideas or suggestions for my specific problem would be appreciated.
Eric

ericsch
varyat's avatar
varyat
145 posts
 
Get your phono pre as far away from your TT as your cables allow and see if that reduces the hum ?
lewm
13,124 posts
 
You had hum with both the old phono and the new JC3+.  You say you can do nothing about the fact that power cables run in parallel with audio cables in your set-up.  In my opinion, that's the first thing you must rectify before you assess any other causes.  AC cords are surrounded by an electromagnetic field, and ICs, especially small signal phono ICs, will pick up the EMI when run in parallel. You have there a known cause of hum, and it probably has nothing whatever to do with the JC3+.  At the very least, separate the AC cords from the ICs by at least 8-10 inches, and see if that ameliorates the problem.  Other ideas: isolate the AC to your CDP and to your turntable from all the other AC feeding your other components.  Both devices can feed EMI back on to the AC line and contaminate other equipment.
bpoletti
1,553 posts
 
Send it back.  It's another Parasound problem.
Post removed 
ericsch OP
753 posts
 
Thanks for the suggestions thus far.

@hifiman5  I will probably call Parasound if I can't solve the problem on my own. I am confident that the JC3+ is in good working condition. I purchased it from a gentleman who sadly had become ill and had to sell his equipment. 

@varyat  I may try that, but it will be complicated due to room considerations.

@lewm  Not the answer I was looking for, but of course you are right. I have to start by fixing the cable routing issue. I have a custom built cherry vertical cabinet. In order to separate the cables as you suggested, I would have to remove all the components and widen the spaces at the back of each shelf to allow for more separation of the cables. Right now the cables are jammed through a small 5 inch opening at the back of each shelf. I had the cabinet built 10 years ago and obviously did not think it through completely. At that time, I had a Rega Fono, with no hum.
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