Recently an audiophile asked a question on AvGuide.com's forum about balance controls. For the uninitiated, balance in this context refers to the ability to adjust the volume levels of the left and right channels independently or readjust their levels relative to each other.
Many audiophiles get by for years, decades even, without a balance control in their systems. Me? I can't get by for more than a week or two max without a balance control...then I usually put something in the system to give me some individual channel adjustments.
With so many DACs, especially USB DACs, coming down the pike without a balance control, sometimes I'm forced to move the balance adjustment functions to the front or the back of the signal chain. Putting the balance control is front is as simple as using Pure Music or Amarra, both of which have channel adjustments available via software.
For Pure Music the channel balance you must go into Pure Music preferences and choose "Audio Settings." There, on the top line you'll see the "right channel gain trim balance" which you must unlock; then you can raise or lower the right channel level. Once adjusted, you can relock the level to prevent accidental changes.
On Amarra you need to make sure the Full Sonic EQ and Pure Gain boxes are checked in the preference panel, then go to the "Panner panel" under the file settings to open Amarra's channel balance control. Once open, you can leave it open on your desktop for on the fly adjustments.
Another solution for those who would prefer an analog solution (or don't use a Mac) is to use active speakers with their own individual trim controls. I'm currently using a pair of PSI A-14M powered monitors, which have a front panel volume adjustment knob. Most powered monitors do have some means of attenuation, which can be used to make channel level changes, and pro-level monitors such as the PSIs also have marked reference calibration levels so you can quickly duplicate levels for critical listening and monitoring purposes.
Of course this all begs the question, "Why do I need channel balance control?" If you listen to only commercial pop releases, you may never have a hankering to change the relative channel outputs. But if you listen primarily to classical, acoustic, and/or non-commercial recordings like I do, being able to make channel adjustments is essential. It's amazing what as little as a .5 dB addition or subtraction on one channel can do for imaging and soundstage solidity and focus.
Obviously, when I make channel balance changes it's due to peculiarities in the program material, not any physical or electronic channel imbalance issues in the system as a whole. If you must adjust your channel balance to one side or the other on a permanent basis, something in your system is out of whack and using a balance control is not the best solution - you have larger issues. But for program-related channel balance correction having a balance control somewhere in your system is IMHO as essential as having music itself.