# Is this the correct way to figure out headphone amp channel balance difference in dB?

#### Pdxwayne

##### Major Contributor
Chain is laptop to Topping E30 to SMSL HO200.

SMSL volume setting is MID.

Headphones used to set volume level is AKG K371.

First I play songs using headphones and determine a good volume level.

Next, at that volume level, I played 240hz tone and measured with multi meter.

Left channel measured at 0.09 V
Right channel measured at 0.094 V

I checked multiple times. Same results. I checked again using 60hz tone, again the channel difference stays at 0.004 V.

I use the first calculator at
to perform voltage to dB calculation.

db difference going from 0.09 to 0.094 is
~0.377db.

Is this a correct way to find channel difference in dB based on measured voltage difference?

Would this mean my headphones right side will be louder than left side by ~0.377 dB, as compare to using amp with no imbalance, when voltage match via left channel?

Thanks!

OP

#### Pdxwayne

##### Major Contributor
Below is Amir's channel imbalance graph for smsl ho200.

At mid gain mode, volume knob at ~11 o'clock, voltage at 0.09, what db would this land in term of that red line?

Also, what does max attenuation = -40 mean? Do I need to care about anything below -40db of the red line?

Thanks!

#### solderdude

##### Grand Contributor
The channel imbalance (and gain) of an amplifier is measured with the volume control at maximum.

The moment you start moving an analog volume control it becomes a crap shoot and can show imbalance differing at each position of the volpot.
Could be small, could be significant.

In the plot above Amir meant: Down to -40dB channel imbalance is fine (within 0.5dB) when you set the volume knob lower the channel imbalance (in that particular amp from that model) the channel imbalance is more than 0.5dB.

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OP

#### Pdxwayne

##### Major Contributor
The channel imbalance of an amplifier is measured with the volume control at maximum.

The moment you start moving an analog volume control it becomes a crap shoot and can show imbalance differing at each position of the volpot.
Could be small, could be significant.

In the plot above Amir meant: Down to -40dB channel imbalance is fine (within 0.5dB) when you set the volume knob lower the channel imbalance (in that particular amp from that model) the channel imbalance is more than 0.5dB.
Thanks!

In that graph, could it also mean that we shouldn't turn the volume knob position too low and should always aim for above 12pm position so the channel imbalance won't get too large?

#### solderdude

##### Grand Contributor
Amir turns the volume knob by hand from max. to min. in a somewhat steady rotation during a couple of seconds (in this case 18 seconds) and logs the voltage so the volume knob position isn't exact.

Analog volpots (especially the smaller sized log-type ones) can be pretty bad from fully left (say 7 o'clock) to volume slightly raised (8-9 o clock)

OP

#### Pdxwayne

##### Major Contributor
Amir turns the volume knob by hand from max. to min. in a somewhat steady rotation during a couple of seconds (in this case 18 seconds) and logs the voltage so the volume knob position isn't exact.

Analog volpots (especially the smaller sized log-type ones) can be pretty bad from fully left (say 7 o'clock) to volume slightly raised (8-9 o clock)
Thanks!

I set volume switch to Low setting and adjusted volume knob to ~1 o'clock position.

Now I got better balance.

Left 0.092 V
Right 0.093 V

I guess going forward, at least for my k371 and my amp, I will use Low mode with volume control pass 12 o'clock position.

Thanks again!

#### DVDdoug

##### Major Contributor
Nothing in the real-analog world is "perfect" and there will also be some imbalance in the headphones. I assume 1/2dB would still be considered "in spec" and if you're lucky the opposite side will be louder.

Your ears aren't perfectly matched either but your brain will automatically compensate for that and you won't notice unless you have severe hearing loss in one ear.

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OP

#### Pdxwayne

##### Major Contributor
Nothing in the real-analog world is "perfect" and th4ere there will also be some imbalance in the headphones. I assume 1/2dB would still be considered "in spec" and if you're lucky the opposite side will be louder.

Your ears aren't perfectly matched either but your brain will automatically compensate for that and you won't notice unless you have severe hearing loss in one ear.
Thanks!

Yeah, for normal music enjoyment, small dB difference under 0.5db should not matter much.

It is only when comparing amps by voltage matching, then the channel imbalance "might" be sensed by some people with very sensitive hearing.

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