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.


the accuphase integrateds are known to have poor implementation of xlr input(s) - they have been measured to be rather noisy compared to the standard rca inputs

but not poor to the point of what is described here - which points to a substantive malfunction


I wasn’t aware of this , I was considering a hair shirt system on behalf a friend and have been looking at Accuphase integrated models as a possible contender, I shall bear in mind.


Sort of spending quite some times to go thru the troubleshooting on the phone, hence thought of posting here to see if there's any other opinions

“the accuphase integrateds are known to have poor implementation of xlr input(s) - they have been measured to be rather noisy compared to the standard rca inputs”


I beg to differ with your feedback. Is this your personal experience? I never heard or experienced such a thing as poor implementation of XLR inputs…btw, Accuphase amps or Integrated are dead noise or hiss. 

"the accuphase integrateds are known to have poor implementation of xlr input(s) - they have been measured to be rather noisy compared to the standard rca inputs"

@jjss49 : more details, recognized Lab measurement results, etc., will be helpful! 

@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 (+) 




I realize that you mentioned that all works perfectly with RCA inputs, but perhaps try changing Left vs Right speaker cables on the amp side (only) to make absolutely sure that the issue is not with the speakers or speaker cables.

Also perhaps you can speak to Accuphase support..

Good luck

@lalitk et al

hey folks, i am sorry -- i didn’t mean to cause undue consternation

i bought a used e270 couple years ago and felt the balanced input did not sound as pure as the rca input, to my surprise (i had a couple dacs at the time that had both single ended and balanced outs and i could hear the difference in my system) - i did not personally try the higher up models, and perhaps those are immune from this issue

after that experience i saw the following information on the asr site -- please note that i am not a ’measurements guy’ in the least, particularly with respect to using measurements as a proxy for sound quality of any given component, but it was interesting to see the findings solely in regard to noise level in the preamp section and thru the xlr input of this tested unit

i also spoke to usa importer briefly on this topic and confirmed this was an area that accuphase japan was working on, as traditionally accuphase gear was exclusively single ended in design, with no balanced connections

thereafter, with the announcement of the replacement model e280, accuphase themselves mentioned that one of the notable improvement areas was in the balanced input noise level - see below page 5



Thanks all, will try any other avenue and see 

@tecknik  the issue is the cable work just fine consistently on right and have swapped cables left and right as well 

@jmarshak speakee cables has been swapped left and right at the amp side as well


i just want to be clear and say that i have tremendous respect and liking for accuphase gear which i have owned on several occasions in the past

it is wonderful gear, so beautifully built and sound quality to die for

my initial response to the op was specifically on the narrow topic of xlr input implementation in their relatively recent pieces

my experience otherwise with accuphase amps have been wonderful, and they have been utterly reliable and absolutely built to last a lifetime

Given the diagnostics performed and assuming that ‘softer’ means lower volume, I assume that either pin 2 or 3 (in any case, not the ground pin) of the left XLR connector in the amp (not the cable) are suffering from a ‘cold’ soldering contact, or more precisely, a hairline fissure (this would explain random ‘recovery’).

Have a technician take a look at the XLR input of the amp.

Good luck

@aschuh hopefully that the case so it's not too big of an issue, will seek for some tech help

@paradis Here is simplest method to check if balanced input functions properly:

1) need to make custom “debug” RCA - to XLR cable, where RCA hot pin to pin 2 + 3 at XLR, shorted together. Shield / RCA GND as ussual goes to XLR pin 1.

2) using this cable, connect source to left and after to right Accuphase balanced input, and check output. 

3) faulty balanced input with this “debug” RCA-XLR cable, will sound significantly louder. Ideally balanced input should not produce any sound, good pre/amp will produce signal at -40dB or lower level. 



Could be bad contacts on the "BALANCED CONNECTION" selector, switch it a few times to clean the contacts and see if the problem go away.

Hi thanks, the balance selector is only applicable for Power in and he's  using the Preamp balance in, but will definitely try

If you are delusionally 'clever' or penurious and buy from overseas grey-market electronics sources you must pay the piper!