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Channel imbalance in amps, turn off thump?

post #1 of 5
2/6/06 at 2:04pm
Thread Starter 
What causes channel imbalance when you turn the volume way down? All my amps do it to some degree. Except my Mint. It remains very balanced all the way down. Do all mints exhibit this?... or did I just get lucky?

What causes the turn off thump in simple OP amp circuits? cmoys, govibe and PA2V2 and the likes?

Thanks,
Garrett
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post #2 of 5
2/6/06 at 2:12pm
I do believe my MINT does have imbalance when you bring the volume very low
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post #3 of 5
2/6/06 at 2:31pm
I think it's because pots aren't perfectly matched in the L/R channels, and this becomes very noticeable at low volumes. I can't really notice it in any of my CMoy's with the Panasonic pots, but it's VERY annoying in my PA2V2.

But I could be wrong, I just made an assumption
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post #4 of 5
2/6/06 at 3:00pm
Channel imbalance at low volume is due to the pot.

Turn off thump can be caused by power rail capacitance ramping down the voltage to the opamp, or excessive DC offset. Putting the cap on the far side of the power switch along with the battery may get rid of the thump.
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post #5 of 5
2/19/10 at 4:27am

On / Off thumps in headphone amps: opamp dependent?

First, on/off thumps in headphone amps are, IMO, a serious issue for delicate IEMs. Most headphone amps I have heard -- including low-gain versions supposedly meant for IEMs -- fail miserably in this aspect. With amps, I always plug-in and plug-out IEMs with amp pwr ON and Volume at min. (i.e., never turn ON/OFF amp with IEMs plugged in). However, one portable amp I have, the Xin SuperMacro IV, "auto-OFF's" once amp batt. pwr gets below some threshold. And, with IEMs, it sounds nasty when it OFF's!
Recently, I was rolling opmaps in the Xin when I came upon an opamp that "auto-OFF'd" w/o a peep: AD825 (liked this opamp a lot anyway ... now one more reason to praise it).
The two Go-Vibes I have (V5b; V5cS low-gain) are also ON/OFF thumpless.
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