JC2 Pre-Amp Left/Right Channel Output difference

sgmsmg · September 2017

So I recently purchased a Parasound JC2BP Pre-Amp (New from Audio Advisor) and it is currently being broken in. Approximately 120 hours or so on it. From my research most say these need about 200 hours or so.

Even though it is not fully broken in I was listening to different test Cds and observed my right channel is definitely providing higher gain ( about 3db or so measured with an SPL meter). I discovered this when I noticed the imaging is shifted to the right side of my sound stage running a Chesky CD and also an ISASCA CD.

So far I have confirmed it is not speaker/palcement related by swapping left and right speaker cables at the Amplifier output. The higher output swapped to the left.

This difference in Left/Right output was not there with my Parasound P5? I have not change any other cables or component since introducing the new JC2 Pre-Amp. The JC2 Pre-Amp does have left and right channel level adjustments but the manual says to set them fully clockwise to remove them from the circuit. I could probably balance the channels with this adjustment but I don't think I should have to. The level adjustments appear to be there for differences in speaker placement/room acoustics.

Could it be that the P5 pre-amp masked this before and now the JC2 is revealing it?

My plan to try and narrow this down is as follows:

1-Swap back to the P5 and confirm that the left and right are balanced
2-Swap Left and right XLR cables 1 set at a time and observe for any changes
3-Run RCA cables from JC2 pre-amp to amp observe for any changes
4-Try another set of XLR cables in different locations

For reference this is my signal path:

Oppo BDP-103D>Ethereal HDMI>Bryston BDA-3>AQ Columbia XLR>Parasound JC2>AQ Columbia XLR>Parasound A21>AQ Castlerock Speaker cable>Polk LSi15

As I just typed this out I thought that maybe if one of the 72V DBS battery packs are dead it could possibly cause a difference in output?

Any feedback/suggestions would be greatly appreciated.

Dennis Gardner · September 2017

Your logic and method of troubleshooting is sound. As a quickie check, plug and unplug all left side XLRs a couple times to insure a good connection and run your test again. If an XLR drops a single run, it will still produce a signal, but it might do it at a reduced dB level.

sgmsmg · September 2017

Dennis Gardner wrote: »

Your logic and method of troubleshooting is sound. As a quickie check, plug and unplug all left side XLRs a couple times to insure a good connection and run your test again. If an XLR drops a single run, it will still produce a signal, but it might do it at a reduced dB level.

Thank you for the suggestion. I will add this to my list and give it a try.

[Deleted User] · September 2017

Good luck sir. I hope it works out.

Emlyn · September 2017

In this case the simplest check is to put the P5 back in place of the JC2. If the balance is still off the JC2 is the culprit and should go back to Audio Advisor during the return window.

sgmsmg · September 2017

rednedtugent wrote: »

Good luck sir. I hope it works out.

Thank you

sgmsmg · September 2017

Emlyn wrote: »

In this case the simplest check is to put the P5 back in place of the JC2. If the balance is still off the JC2 is the culprit and should go back to Audio Advisor during the return window.

Yes, I completely agree. Just wasn't sure that the difference in noise floor between the two pre-amps could reveal this problem that the P5 was masking.

I will try and do the swap back this afternoon. Working night shift so if I started tinkering now I would be sacrificing some needed sleep.

Emlyn · September 2017

I have had the same problem with a couple of tube preamps over the years. In both cases the preamp output circuit on one side was the problem. Of course it took me an hour or more trying to figure out if it was source component, cabling, the amp, the speakers, or an ear infection causing the problem. Annoying!

tratliff · September 2017

Might want to give Parasound CS a call. They are very helpful.

kharp1 · September 2017

I assume you're running balanced (XLR) cables only? I had an issue with 2 different sets of XLR cables on my P5. I went back to RCA to verify it was a cable issue as opposed to tube issue in the amp or other problem with the P5.

sgmsmg · September 2017

Thanks for all the suggestions.

I finally had some more time to investigate this further.

Ultimately by swapping pre-amps/checking cable connections it seems the problem may be gone.

There was nothing obvious so no smoking gun. More than likely it was a connector not being seated properly like a few people mentioned and would seem the most obvious. However on the JC2 the XLR's lock in place and make an audible click when inserted so it is strange that it was potentially the issue.

Everything is back to original and swapping between the P5 and JC2 seem to yield similar results.

With a constant test tone out of each channel the left and right channels are within 0.5db or less.

Running two different L<->R sweep tests the sound stage appears pretty centered. I swapped L/R outputs to make sure it matched in either configuration.

Still evaluating if the JC2 is worth the upgrade.

ukcolin99 · September 2017

edit

[Deleted User] · September 2017

Glad it is working out. So does the "problem" follow the cable?

I'd be looking for a lower noise floor. they it has no noise in the reviews..
more space and better defined Instruments in the soundstage...
more smooth musical goodness....

JC2 Pre-Amp Left/Right Channel Output difference

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