[derbigpr]

For reasons explained in this post, I'd like to ask you to take a listen to this 30 second video and tell me where exactly do you hear tones from left, right and center channel.
https://www.youtube.com/watch?v=_Rlnp7wRnKs
 
Is any of the tones obviously louder than others, is the left or right more pronounced, are they the same in terms of height and depth, is the center channel coming exactly from center or slightly offset? I wont tell you how I hear them in order to eliminate placebo since you will expect a certain result instead of hearing it for yourself.
 
 
 
This topic of channel imbalance has been bothering me quite a lot lately. I have a feeling that some of my amps are veeeery slightly louder out of one channel. The difference might even be placebo (even though I'm pretty sure I've eliminated that by playing mono tones trough in-ear headphones and putting the earphones in my ears randomly, without knowing which is left and right, and always I can tell that one is slightly louder than the other, sometimes in left and sometimes in right ear). I know all amps have slight imbalances, but it's bothering me greatly when I know a vocal should be in middle but I hear it slightly towards left or right.
 
The issue is that I don't hear those differences out of many sources that in theory should be inferior. For example, I don't hear channel imbalance out of a cheap laptop or a smartphone, but I do out of a 900 dollar headphone amp. Reasons for that might lie in the fact that a headamp has a wider soundstage and less crosstalk between channels, so any sound on a record that might be recorded slightly off-center will sound more off-center on a headphone amp.
 
 
 
I've tried to measure the headphone outputs of various amps to see whether there are any differences and I'm getting some results that don't match with what I'm hearing.  The way I'm measuring is I'm using a cable from the Denon D600 headphones which is terminated in a 3.5mm stereo jack on one end, and two 3,5mm mono jacks on the other end, that go into the headphone drivers, one carries a left and the other a right signal. I'm connecting the stereo end into headphone output, and the 3.5mm mono end into the soundcard microphone input and then I'm using a tone generator to create sine wave tones which go trough the headphone amp into the microphone input.  On the input side I have a digital level meter, which basically enable me to check levels from the left and right channel separately and compare them.  In the example of NAD D1050 DAC/headamp, I'm getting a consistent result all across the board, with volume knob at almost minimal volume level, at mid-level and at full volume,  and measured at 40, 200, 500, 1000, 4000, 8000, 12000, 20000 hz. Right channel is always 0.1 dB louder. Which is as good as it can get, impossible to tell the difference by ear.  However,  I hear imbalance in favor of the left channel. To my ear it's between 1 and 2 dB louder, and I can tell that because I hear both channels balanced when I reduce the left one by about 1.5 dB.  So it's not a big difference, but it still is different.
 
 
The thing is...why do I hear a difference if they meassure identically in terms of level on all frequencies and volume knob levels?   For example, the iPhone 4S meassured in the same way is absolutely identical in terms of it's channels, no differences whatsoever, and I can't hear a difference either.  My laptop's headphone out the same thing, it's getting some 0.1-0.2 dB variations at certain frequencies, but again, it's dead centered to my ear.  So why does the NAD D1050 (and Musical Fidelity M1HPAP to a larger extent) sound slightly off-center to the left if it meassures equally on both channels?
 
I'm assuming it's because there's no load or resistance that the amp has to deal with, since the headphone out basically just acts as a line out into the microphone input on the soundcard.  Is it possible that with some load the measurement would be different?
 
Do you guys have similar experiences of hearing channel imbalances?

 

[ab initio]

If you can post a 30 second sound clip or two of a couple of sections of music where you think you hear channel imbalance, I'd be happy to calculate the spectral energy in each channel for you to see if the imbalance exists in the recording or not.
 
Cheers

 

[derbigpr]

  If you can post a 30 second sound clip or two of a couple of sections of music where you think you hear channel imbalance, I'd be happy to calculate the spectral energy in each channel for you to see if the imbalance exists in the recording or not.
 
Cheers

 
 
Hi, thanks for the offer, I'll try to cut out some files later and do that.
 
But what do you think about that video I've posted in my first post? Do you hear the center channel exactly in the middle or pulling to either side?

 

[ab initio]

   
 
Hi, thanks for the offer, I'll try to cut out some files later and do that.
 
But what do you think about that video I've posted in my first post? Do you hear the center channel exactly in the middle or pulling to either side?

That video sounds okay to me after a quick listen.
 
I will say, that I often notice that I sometimes notice that some recordings sound like they aren't balanced L/R; however, the waveforms from each channel usually match what I hear.
 
 
Cheers

 

[derbigpr]

 
That video sounds okay to me after a quick listen.
 
I will say, that I often notice that I sometimes notice that some recordings sound like they aren't balanced L/R; however, the waveforms from each channel usually match what I hear.
 
 
Cheers

 
 
 
I hear that video with a center sound slightly to the left...but VERY slightly. If I reduce the loudness of the left channel from 100 to 96 in the microsoft sound settings (which is slightly more than 1 dB of change, then it sounds centered.  This is basically my issue, the fact that imbalance is so slight that I never know whether it's on the actual recording or it's the gear.

 

[ferday]

i listened on two systems (computer speakers and headphones) and it sounds fine to me
 
i would be suspect of a youtube video recording quality before i started to worry about my equipment...but...it's pretty common for amps to have small channel imbalance, especially in the lower volume registers.  

 

[derbigpr]

  i listened on two systems (computer speakers and headphones) and it sounds fine to me
 
i would be suspect of a youtube video recording quality before i started to worry about my equipment...but...it's pretty common for amps to have small channel imbalance, especially in the lower volume registers.

 
 
Sounds fine to me as well out of a laptop, iphone and integrated amp, but slightly to the left with Nad D1050 and Musical Fidelity M1hpa.

 

[derbigpr]

Could it be possible that measuring the left and right channel outputs out of a headphone amp could be different when only connecting it to a microphone input than when connecting actual headphones that present some load for the amp?  Is it possible that even though trough the mic in both channel shows identical voltages, they could be sending varying voltages to the actual headphone drivers?

 

[ab initio]

  Could it be possible that measuring the left and right channel outputs out of a headphone amp could be different when only connecting it to a microphone input than when connecting actual headphones that present some load for the amp?  Is it possible that even though trough the mic in both channel shows identical voltages, they could be sending varying voltages to the actual headphone drivers?
 
 

Certainly. The mic input has very high input impedance compared to a headphone's impedance. If each channel's output impedance of the amplifier is appreciably different and relatively high (several ohms), then it there would be a channel imbalance in a low impedance headphone that would not show up in the high impedance measurement device.
 
I would like to add that if you have different devices present the Left/Right balance differently, then certainly at least one of those devices is not working correctly.
 
I would also like to second freday's comment that it is very common in amplifiers with analog potentiometer volume controls that at low volume settings there is noticeable channel imbalance. This is one of the problems with very high gain headphone amplifiers.... many headphones with normal to high sensitivities require the volume knob turned down low enough that there is noticeable channel imbalance. Try using software volume control to knock the software volume down 10 or 20 dB and turn the volume knob up on your amp and see if you still have channel imbalance.
 
Cheers

 

[derbigpr]

  Certainly. The mic input has very high input impedance compared to a headphone's impedance. If each channel's output impedance of the amplifier is appreciably different and relatively high (several ohms), then it there would be a channel imbalance in a low impedance headphone that would not show up in the high impedance measurement device.
 
I would like to add that if you have different devices present the Left/Right balance differently, then certainly at least one of those devices is not working correctly.
 
I would also like to second freday's comment that it is very common in amplifiers with analog potentiometer volume controls that at low volume settings there is noticeable channel imbalance. This is one of the problems with very high gain headphone amplifiers.... many headphones with normal to high sensitivities require the volume knob turned down low enough that there is noticeable channel imbalance. Try using software volume control to knock the software volume down 10 or 20 dB and turn the volume knob up on your amp and see if you still have channel imbalance.
 
Cheers

 
 
 
 
On the NAD D1050 volume knob is digital, well, at least it's one of those that turn infinitely and changes volume by 0.5dB increments. I have tried all kinds of headphones at various volume levels, from almost all the way down to full on the amp and reduced to about 20% in the software, but imbalance is always identical. When I change the balance of the output in the windows sound settings so that the left channel is at 96% and right at 100%, then it sounds balanced to me.

 

[ab initio]

Hmmm. It sounds like you may indeed have channel imbalance in your amp. You may consider contacting the amp manufacturer, especially if you are still under warranty. There's no reason an amplifier should have noticable channel imbalance.

Cheers