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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

Showing 15 responses by ericsch

ericsch OP
751 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.
ericsch OP
751 posts
 
@helomech I have another stock headshell with a Shure V15 V-mr and the hum remains. The Sillnote is designated as a phono cable.  I'll try some of your other suggestions and possibly some cable swaps.

@yogiboy  I'll try the cheater plug.

@invictus  bpoletti was duly ignored. I've had a Halo 5 channel amp in my home theater system for many years. It has never failed me.
 
ericsch OP
751 posts
 
@lancelock  Does your setup allow you to separate the power cords and audio cables?
ericsch OP
751 posts
 
@lewm Brilliant! I'll give that a try soon. Thanks. 
ericsch OP
751 posts
 
How about the unused balanced inputs on the JC3+?  Could they be contributing to the problem. I have them covered with tape to keep the dust out.
ericsch OP
751 posts
 
@dweller  and others I will try the various things you suggested as soon as time allows. I will probably start with moving the JC3+ away from the rest of the system. I have visitors coming for the next 3 or 4 days. Thanks to all for your responses.
ericsch OP
751 posts
 
Thanks for all your great suggestions. I will be trying some of these things over the next few weeks. I will report back. 
ericsch OP
751 posts
 
Invictus said:
"Do me these two tests.

1.) Disconnect the turntable from the JC3+, but leave everything else connected. Short both RCA inputs (center hole to outer sleeve) on the JC3+. Now turn the volume up and report back if the hum is still present."

@invictus505 I did the above, shorted both inputs, the hum is still present, actually louder than before.
ericsch OP
751 posts
 
OK, did that, no hum, silent.
It is a clean tone about 60Hz, no buzz.

ericsch OP
751 posts
 
I will try this tomorrow afternoon, I'm busy for the rest of the day. Thanks.  
ericsch OP
751 posts
 
@bpoletti 
Butt out, I live 2 hours away from Parasound headquarters in SF. 
ericsch OP
751 posts
 
Thanks to all for your help. I'll call Parasound tomorrow.
ericsch OP
751 posts
 
Getting closer. Short both inputs on the JC3+ again. Pull the JC3+ out and place it somewhere in front of the Cayin, or hold it in your hands if you have too. Use a spare RCA cable (not the pair that runs parallel to AC cords) and connect the JC3+’s outputs to Cayin’s inputs. Turn everything on, hum still there?

@ invictus
I did the above and pulled the JC3+ about 8 feet away from the rest of the system. The hum is still present, although not quite as loud as when the turntable is connected. I can hear it at 1/4 volume. What do you think? 
ericsch OP
751 posts
 
@invictus505

OK, I tried a few other combinations:

1. When the JC3+ switch is changed from MC to MM, the hum is reduced, barely noticeable at 1:00.
2. When I connected the PS Audio GCPH with the same shorting plug setup to the Cayin, no hum except with the gain dial on the GCPH at full open and the Cayin at full open. During normal use the gain dial it is set at about 1:00. I walked the GCPH within a few inches of the Cayin, still no hum.
3. I then pulled out an old Sherwood receiver that i use in my garage system. Connected it to the JC3+, hum audible at 1/4 volume.
4. I then connected the GCPH to the Sherwood receiver, no hum.

The tubes on the Cayin are not stock and have low hours. I realize it’s a Chinese amp, but counterfeit parts? Prima Luna too?

It seems the JC3+ may be the problem.

ericsch OP
751 posts
 
I just wanted to follow up and let you know that I received my JC 3+ back from Parasound last month and they found no problem or defect with the unit. With that reassurance, I am going to review and try some of the suggestions you guys recommended. Thanks to all for your responses.
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