[ProtegeManiac]

Alright, first off, I can't DIY any work on this, and I already know it'll be hard to diagnose the problem, but I've just run out of ideas on how to get this amp fixed. I'll describe the problem and the steps taken so hopefully someone gets an idea of what I can try next (as well as why I'm posting it here out of frustration).
 
Phase 1 : Cantate.2 exhibited mono sound, everything very narrow in the center; output was too low; had some crackling noise also that progressively got more severe as I continued eliminating other possible sources (source, cables, etc)
 
Phase 2 : Technician for a HiFi store near my area diagnosed the amp, said the problem was dirty RCA ports. I said the problem persists even when using the USB inputs. He then says the op-amps - LM6171 - need to be replaced; I contacted the local distributor, and they had none in stock locally, so I need to pony up cash for the op-amps, the shipping cost from Jakarta, and the import taxes. Emailed the tech the links to the op-amps since there were several versions, he insisted they're all the same and it doesn't matter. After spending around $65++ importing them, turns out I ordered surface mount chips that were also too small instead of through hole chips.
 
Phase 3-a : I went to the Shanling distributor since I hoped they might have access to parts, since Shanling mass manufactures Meier amps. Their technician diagnosed the amp, and said the op-amps - six LM6171 - need to be replaced, along with four BUF634T chips. I spent $70+ buying them from DigiKey and sending them to my brother's house in California while my uncle was there so he can carry the chips home instead of me blowing money on shipping plus taxes again. Gave the tech the new chips, and then he'd call me back when they were done.
 
Phase 3-b : Moment of truth as I picked up the amp. Sound was a little soft, but there was stereo separation in the Chesky test track and I chalked it up to the noise of the HT system running there. Took the amp home and had it side by side with my Rega Ear. Cantate2's sound really was too soft, the sound was mono once again, and a few minutes later the crackling was back. Note that by this time I was using a different socket and a different power strip, while the Rega Ear had been using up to that point the same socket and power strip the Cantate.2 was using before.
 
I really have no idea on what to do with this amp at this point. Does anybody have a guess? Should I try getting a new pot? Should I have it modded to have the signal bypass the Crossfeed circuit?

 

[arteom]

How's the volume knob? Dirty? Have you had it off for any extended period of time (several months)? Symptoms you described could possibly point to a faulty/dirty volume knob. 
 
One thing you can do is just go through some rotation cycles, rotate to max volume and back, do this about 50 times. See if the sound has improved at all after you did this. 

 

[ProtegeManiac]

  How's the volume knob? Dirty? Have you had it off for any extended period of time (several months)? Symptoms you described could possibly point to a faulty/dirty volume knob. 
 
One thing you can do is just go through some rotation cycles, rotate to max volume and back, do this about 50 times. See if the sound has improved at all after you did this. 

 

The tech said he would point to the pot last because, according to him, being a sealed unit it's unlikely it would get dirty. However, as much as it's sealed, I'd think that would only be a better guarantee if the chassis is also, and while there's a cover on the vent there's still a vent. The insides were surprisingly clean but  there was some dust. At the very least though the tech reported that measurements were normal after putting in the new chips.

 

I'm gonna try that out now and see if it helps. Will report back ASAP.

 

 

UPDATE : After 50+ cycles on the volume knob the sound just got worse - more noise, less music, and now there's some kind of high pitched signal going through. 

 Is that still an indication that the pot could be the problem?

 

[MisterX]

My guess is the pot is fine.
Somebody is actually going to have to get busy with a meter and scope to troubleshoot it.

 

[ProtegeManiac]

  My guess is the pot is fine.
Somebody is actually going to have to get busy with a meter and scope to troubleshoot it.

 
Yeah Dr.Meier just reminded me it's an active ground design so the tech might not have taken that into account. In any case I've contacted the last possible resource - a DIY-er here who has built some active ground CMOYs and AFAIK does complicated repair jobs. I just hope he isn't too busy these days. Lots of speaker amps and DACs in his FB Page.