[purrin]

^ It's possible the op-amp could be oscillating. Bump up the gain a little if the problem comes back.

 

[ETAHL]

Quote:

Seems swapping signalcables somehow helped me tremendous with the ground-noise. Don't know why - they'we worked flawlessly  up to now - but hey - whatever fixes it makes me happy. Back to being gobsmacked by the magic of this amp. It's THAT good <3 

Cables can do it to you. Keep them short and use decent cables. Some of the stuff you buy at the stores are questionable, even if they look nice and pricey.
I just build my own using the stuff that professionals use. You can make them to the length you need and it is inexpensive to do. I like the Canare GS-4 cables and Neutrik RCA plugs.
These guys carry all you need: http://www.redco.com/default.asp

 

[Jibbie]

Installed the LME49860 today.  I pushed it in a little too hard and was worried I bent some of the prongs, but the amp works just fine.
 
Impressions:  Bass extends a bit more than the stock opamp.  Impact might be slightly slightly less, but the more focused and deep image of the new bass makes up for it.  The highs are a bit sweeter, which is perfect for my Pro 900s.  The Ultrasone's have some sharp highs sometimes, and the new opamp makes the highs a bit more realistic and calm (while still maintaining awesome extension).  The only other difference I can hear is the blackness of the background.  The new opamp provides a much more clear, black background to the music, enabling me to hear each instrument more clearly.  Consequently, soundstage seems to be a bit deeper/wider.
 
These differences are subtle but noticeable, and for the 10 dollars I paid for 2 of them, the LME49860 is definitely worth it (which is good, because I totally bent the stock opamp when removing it haha). 

 

[Jibbie]

Also, I've noticed that my albums have a much more noticeable difference between their volume levels.  Is this normal?  I usually always could listen to almost any album of mine without having to mess with the volume on my Matrix.  Now with the LME49860, however, some albums are louder and some are quieter.  Hopefully this is normal

 

[Vargtass]

Tell me more about this issue.
My problems have come back - seems it wasnt the cables at all. 

I still have huge amounts of ground loop noise, whatever gain setting I use. With more gain, the problem comes earlier. What I do notice is that the ground noise hum disappears if I turn the volume knob to max volume. Weird ... 
 
I can also report that Im working with tamsaudio on this - and he asked me to open the amp and check solderings. Everything looks great inside, but me and my somewhat tech-handy friend cant find anything wrong. 
 
So, any suggestions? I really dont want to sendt the amp all the way back to china to have it checked out - then back to Norway. I love this amp, I can't stand waiting for it for another month or so. 
 
Help guys, let's brainstorm this and fix it  

 

[sunneebear]

Pot grounding?

 

[ETAHL]

 
Quote:

Tell me more about this issue.
My problems have come back - seems it wasnt the cables at all. 

I still have huge amounts of ground loop noise, whatever gain setting I use. With more gain, the problem comes earlier. What I do notice is that the ground noise hum disappears if I turn the volume knob to max volume. Weird ... 
 
I can also report that Im working with tamsaudio on this - and he asked me to open the amp and check solderings. Everything looks great inside, but me and my somewhat tech-handy friend cant find anything wrong. 
 
So, any suggestions? I really dont want to sendt the amp all the way back to china to have it checked out - then back to Norway. I love this amp, I can't stand waiting for it for another month or so. 
 
Help guys, let's brainstorm this and fix it  

Have you try another input source? A portable source like an Ipod would not have any grounding issues.

 

[Vargtass]

Quote:

Pot grounding?

Could be. I'll try to check for it, and maybe change the pot if I can find something similar. 

 

[Vargtass]

Tried both with and without source, plus different sources. Same hum, sadly. 
 
Dunno if it makes sense, but the other day I lifted the front of the amp about 5 inches up in the air, something said "pop" softly and suddenly the hum disappeared. Could that be something with the pot? 
 
Being an amp-detective is kinda cool, I gotto admit. I even have a backup-amp  

 

[ETAHL]

Wiggle the input connectors and power connectors, both the outside and inside ones, to see if the problem is intermittent, It could be a cold solder joint at the connectors to PCB.
Also turn the M-Stage over with the cover open and gently blow out the whole circuit board with compressed air, just in case there might be some tiny metal shavings that might have fallen on the PCB when you unscrew and open its cover.

 

[purrin]

You can try loosening and re-tightening the hex bolt (on the outside bottom of the chassis) that secures the transformer to the PCB. This fixed the hum issue for me.

 

[Jibbie]

Oh wow, somehow ReplayGain was enabled on Foobar when it previously hadn't been.  Turned it off and no more volume differences.  Wasn't the opamp after all 

 

[Vargtass]

Quote:

You can try loosening and re-tightening the hex bolt (on the outside bottom of the chassis) that secures the transformer to the PCB. This fixed the hum issue for me.

This suggestion by purrin "seems" to have fixed my amp for now. 
 
I really tightened the screw, powered up the amp with stock opamp and with no source whatsoever, and heard NO hum whatsoever. Delighted by this, I proceded to install the 627 opamp and test again. The amp once again produced no ground feed hum, so I tested it connected to my dac, and I'm using it right now, happy as a little panda over the fact that the amp no longer produces any unwanted noise. Once again, it just delivers fantastic sound to my Denons. 
 
I won't know for sure if the problem is permanently fixed, but I gotto say, things are looking very good. 
 
I would like to thank every one of you that has contributed, and also to tamsaudio from whom I've recieved mails from regarding this. Top service! 
 
Thanks everyone! Music awaits  

 

[Mad Max]

 
Quote:

Have you try another input source? A portable source like an Ipod would not have any grounding issues.

iPods actually help with grounding issues, lol!
 

 

[ETAHL]

Quote:

 

iPods actually help with grounding issues, lol!
 

It is isolated, no AC ground loop issues running off batteries. Is that the better description you are looking for?