JC3+ phono preamp

Not sure if this goes under  amps/preamps or analog.

Bought a new Parasound JC3+ from Audio Advisor.   Took delivery last week.

I was replacing a Dynavector 10x2 HO MC on a VPI Classic 2, appox. 7 years old. Using VPI's  own turntable interconnects. 

JC3+ was hooking to an integrated Yamaha AX400 (don't laugh; it sounds good and has gone 33 years with one checkup, and one repair).  The Yamaha has a decent onboard phono pre, with MM/MC settings. Resistance is not user adjustable. I'd guess it defaults to 47 Ohms? Not sure. 
I hooked up the JC3+ to a line stage, "Auxiliary"  on the Yamaha. Not to the phono stage.  

The old  Dynavector seemed to have developed issues in the right channel. Continuity tests on my end, followed by double check at local repair shop seemed to confirm. So, while cartridge shopping, decided to go semi-big, for me, and ordered the JC3+.

Upon installing the JC3+ with the Sumiko, problems developed with the JC3+.

First, the JC3+ is a  hummingbird.  Seemingly, the dimmer switched lights in the room where the stereo is parked caused an annoying hum, even when the turntable connects were grounded. When I turned those lights completely off, hum went away. So long as I use a miner's light or natural daylight, hum is fixed, I guess. 
The Yammy, by contrast, does not hum, at least not to any annoyingly audible degree.
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With the JC3+ in the signal path, everything plays beautifully through one channel.  The other channel is so faint, you have to put your head a foot from the speaker to assure yourself it is not a dead channel.  If you adjust the balance knob on the Yamaha maybe three clicks, then turn the overall volume up,  you get something approaching a normal soundstage and balance.

Without belaboring how much of my weekend I spent checking various things, VTF (dead on at 2.2 to maybe a little high, which is what VPI recommends);  azimuth (close, I think, but not checked with anything more than VPI's jig), various cable combos, two sets of speakers, through A/B circuits of the amp,  anti-skate (which VPI discourages, but includes on the Classic 2) disabled/enabled, nothing changed. One channel consistently faint. 

Then here's what I found: Taking JC3+ out of the circuit completely, VPI hooked directly to Yamaha's internal phono pre, it played without issues (no  audible hum, either, btw).  No channel balance issues.  Is the onboard pre as dead black quiet as the JC3+, judging by the one good channel I'm getting from the former?  Maybe not quite, but darn close.  This is a 33 year old integrated, that I bought for less than $300 new.  The JC3+ sells for close to $3 grand. 

One can hook a JC3+ or other separate pre-amp to an input line of an integrated, right? 
No horror stories about Parasounds not getting along with Yamahas?

Build quality issues at Parasound?  I've got two ZPhono USB Phono pres, which sound great, especially for the money. They seem like little tanks, no issues.

Anyone see anything I've done wrong or overlooked here? I want to emphasize, it is not a minute difference in sound between the two channels.  Very pronounced and noticeable. 

I am preparing to send the thing back to Audio Advisor.  But if I'm leaving out some step, or anyone has a suggestion, I bought the thing with the expectation of getting something that was supposed to be among the best in its price class.