[derbigpr]

  In most cases it is not the fault with the amp. It can be a problem with a difference in impedance between the left and right headphone driver. This then affects the rms voltage to the drivers. It is especially noticeable on low volume levels.
But more surprisingly, it can be a hearing imbalance. I am one of those who has such a problem with my hearing and need to use a headphone amp with a gain offset.

 
 
 
Yea but when you plug a headphone into one amp and it's perfectly fine, then plug it into another, and then there's imbalance, you can't say it's a driver impedance problem or a hearing problem. And the fact is, most headphone amps, even expensive ones have this problem.  They put all kinds of expensive components inside the amps, more importantly they load them up with useless components that do close to nothing to the actual sound in order to increase the percieved value of the amp, so they could sell 30 dollars worth of components inside a 50 dollar metal enclosure for 1000 dollars or more, but they can't invest in a proper volume control. I'm currently very pissed about it since my last amp was sold and exchanged for a new one just because of channel imbalance, and guess what, this one has the same issue as well. So it's like 8/10 chance in my experience that a headamp is going to have channel imbalance.  Frustrating even more when I plug my phones into an iPhone or a laptop, which only have maybe 5% of their cost invested in sound,  and it's perfectly balanced.

 

[SourceGuy]

  It's interesting how headphone amps manufacturers can be so incompetent to not get rid of channel imbalance. I've had the same problem with pretty much every headphone amp I've owned so far, including the quite expensive Musical Fidelity M1HPAP which costs 900 dollars, as well as the Nuforce HDP, Little Dot mK5, mKIII,  Musical Fidelity V-CAN II, etc. Interestingly, my very cheap laptop (like 400 dollars) doesn't have any channel imbalance, Asus essence st doesnt either,  neither does the iphone 4s, or samsung galaxy s3, or a 20 year old philips receiver, or an onkyo integrated amp or a Panasonic plasma tv headphone output.  But headphone amps, designed to do one thing and one thing only, do have imbalances. Makes you wonder why you'd pay for them if they can't even do the basics right.

Very well put.  I've experienced this with headphone amps in the past. The HA-540 being one of them.  Sent it back to them twice and they still never fixed it.  They claimed a bad tube the first time even though I had tried 6 different tubes in it.  Second time, they claimed there was a solder bridge that they repaired.  It always went back to a strong channel imbalance after a good 20 hours of listening.  I can't agree with you more, channel balance is so fundamental.  Like you, I have only experienced channel imbalance with dedicated headphone amps and never with simple devices like laptops, cd players, or iphones.
 
When there is channel imbalance it is the most annoying thing.... I can't listen to it. The whole time I think I'm deaf in one ear...

 

[Mediahound]

Did you ever get this figured out? I'm asking because I thought I had this problem too with my Schiit Mjolnir 2.  But I did some listening tests and it turns out the tracks I tested sound exactly  the same in terms of some channel imbalance when played with different headphones, directly out of my iPhone, as they do when using my new Schiit Mjonir 2.
 
Further searching, I found this thread:
 
http://www.head-fi.org/t/501948/stereo-imaging-vocals-towards-left-side
 
It turns out, stereo vocals are usually skewed a bit to the left. I guess if your left channel seemed lower, than you really did have some issue with your amp or DAC. 
 
I was however relieved when I played the same track on my iPhone with different headphones and the vocal sounded the same, skewed slightly to the left. 

 

[noway]

Maybe a silly question but why not use a meter hooked up to the output(s) and a test CD to measure the difference between right and left? That way you are measuring the amp, not guessing with your ears and confounding it with your headphone variations.

 

[Scrith]

I'm resurrecting this old thread because I'm having a similar channel imbalance problem with my 3-month old Lyr 3. Basically, starting yesterday (it had been fine until then) the right channel gets significantly louder than the left channel at 10 o'clock (lower volume settings sound fine) on the volume knob (for both high gain and low gain). The problem slowly improves as I turn the knob and disappears completely at around 12 o'clock on the volume knob. The problem started about an hour into listening to a Russian Foton tube (before that I spent 1-2 hours listening to a similar Russian Melz tube without any problems).

I've tried swapping headphone cable channels (Aeon Flow Closed headphones make this simple), flipping the channels in my software (JRiver Media Center), cleaning the tube socket (all 8 holes) carefully with an isopropyl alcochol wipe, and changing tubes, but nothing seems to solve the problem. I'll be talking to Schiit about the problem, but I'm curious if anyone has other suggestions I can try to resolve the problem without sending the amp to Schiit?