Accuphase E650 XLR Input issues

I'm asking on behalf of a dear friend, he has an Accuphase E650 which was used on RCA input without any issues, recently with an upgrade of the source, XLR was chose as the preferred connection.

It works fine initially, however just after few days, the left speaker start to sounded noticeably softer than the right, sometimes it normalise sometimes it stay on as is for long period of time, these were done as isolation steps:

- Continue to use RCA input, works consistently

- Swap left / right XLR input, still the left speaker softer noticeably

- Swap different DAC with XLR output, still the same behavior, left speaker softer noticeably

- Tried different XLR cables, still the same behavior, left speaker softer noticeably

- Tried both the XLR preamp input (CD-in, and Balance-in), same behavior, left speaker softer noticeably


Ran out of options, the challenges was the amp was purchased from an oversea distributor, getting local dealer support can be a hit and miss, trying to post this up to see if anyone ran into such issue before and also seeks some opinion.


@lalitk 100% agreed! My experience with Accuphase components is positive, and in my setup all Accuphase components produce ZERO background noise! 

@paradis "I'm asking on behalf of a dear friend” 

if your “friend’s" question is targeting to collect Accuphase reliability and performance feedback,  my personal experience w/ Accuphase is 100% positive. 

" sounded noticeably softer than the right” - Can you please help to understand what exactly technical problem is, such as but not limited to distortions, tone/EQ ch difference? 

@westcoastaudiophile it just means the left channel is considerably softer and once it normalized (sometimes few minutes after playing music), it just wake up with the right volume, sometimes it doesn't wake up at all, if that makes sense based on the explanation, no such issue if RCA being used

@paradis sounds like this is a real functionality issue, I would start debugging it with balanced input preamp inspection.

One thought here is that Accuphase Input / output ( balance) XLR is wired differently then most , try a cable wired at the input side per below from accuphase website.

1, Ground 

2 Inverted (–)

3 Non-inverted (+)