Possible Channel Imbalance[Solved]

[XforceVesa2]

What's the channel balance of your source?

I use as a Source the iFi Micro iDSD Black Label. The Crackatwoa is directly connected with the RCA LineOut from the iFi(the switch on the iFi for the LineOut is set to "Direct"(it's basically a passthrough) so that the Volume control from the iFi doesn't interfere with the RCA LineOut.

I've got the Following measurements directly from the RCA Output from the iFi:

L = 1,434V

R = 1,463V

So an imbalance of about 0,2dB

The strange thing here is that it seems like that the right side is louder than the Left side before it goes trough the amp. It's like that the channel in the amp gets inverted?

EDIT: Out of Curiosity I've did an hearing test to determine the Loudness differents between two channels via the Site Audiocheck.net what I'm able to hear.

The tests shows me that I can reliable tell a loudness different with 1dB but with 0.5dB I couldn't reliable tell if there's a channel Imbalance or not.

I've did a test with my other(cheap) Headphone and the strange thing here is that it seems like that on this Headphone(It's a Headphone with USB Plug that I'm using on my Main PC) the Left Side also to be seems louder than the right side and if I turn this headphone I can clearly hear that the right Side is louder than the Left side(This Headphone wasn't plugged in my Music PC nor in the Crackatowa). That all doesn't make sense   

So technically I shouldn't be able to Hear this Channel Imbalance of 0.3dB as Doc. B stated 

[Paul Birkeland]

The brain is a rather mysterious organ. 

If you want to compensate for all of this, it's probably possible to adjust the resistor values on the coarse side that's louder to compensate, but that seems a little bit intense for what this is.

[Thermioniclife]

Hey PB.
I am resisting the urge, Should I just relax?

[Raymond P.]

If the imbalance you're hearing still bugs you, you could consider replacing the stepped attenuators with the analog pots so you'll have the balance control and listen to that for awhile. Who knows, the sound may be agreeable.

[Thermioniclife]

Ditto! or relax and enjoy. Or buy 0.1% tolerance passive parts and stress about something else about your life.
You have stated that your source has an imbalance so get real!

[XforceVesa2]

Ditto! or relax and enjoy. Or buy 0.1% tolerance passive parts and stress about something else about your life.
You have stated that your source has an imbalance so get real!

It seems like that makes you a little stressed out as soon as I ask a Question. You always seems to answer me that I should e.g. relax, chill instead of giving me a normal Answer as the Other Users in this Forum did.

As I said I did a Hearing Test to determine if I'm even able to Hear this Channel imbalance(at the moment only 0.3dB). It seems like that I can only reliable tell a Difference with an imbalance of about 1dB what means that I can't tell a difference with 0.3dB.

I get it that the whole Thread is possible pointless as even an imbalance of 0.6dB I can't hear.(What I discovered at the Hearing Test)

Even as (in my opinion) your answers was a little bit rude, I think you've got a point with "relax and enjoy".

I would like to Thank the Forum for the patience to Answer my Questions and I think the best thing I can do with the Crackatwoa is simply to "relax and enjoy" the Sound of this Amp.


Out of Curiosity I have a last Question about the Amp. Does the L and R channel get inverted as it goes trough the Amp?


Just a little Edit: Sorry if some words or sentences that I write could be wrong interpreted as it's not my native language.

[Deke609]

Does the L and R channel get inverted as it goes trough the Amp?

Just to clarify, I think you are asking whether the amp swaps left and right signals - i.e., whether the left input signal appears on the right output rca jack, and vice versa? I assume you mean this because you've measured the channel imbalance of your source and found that it is opposite to the imbalance coming out of your C2A, and so your hypothesis is that the amp swaps left and right signals, thereby passing on the imbalance of your source. Do I have that correctly?

(I ask the above clarifying questions b/c in audio-speak the term "inverted" often refers to phase inversion - i.e., if you imagine a sine wave signal with a positive peak at time 1 and a negative peak at time 2, the inverted version of that sine wave would be flipped 180 degrees: a negative peak at time 1 and a positive peak at time 2. I don't think you are asking about phase inversion -- but please correct me if I am wrong).

Re whether left and right signals are  swapped: I'm pretty sure that none of BH's amps swap left and right signals b/c (a) that would significantly change the presentation of music (e.g., horns that should be on the left are instead on the right), and (b) I can't imagine any circuit design reason/benefit to swapping signal sides. I think the only way for the signals to get swapped is by user/builder wiring error - my guess would be at the attenuators. So you might want to double-check your signal wiring.

cheers, Derek

[XforceVesa2]

Just to clarify, I think you are asking whether the amp swaps left and right signals - i.e., whether the left input signal appears on the right output rca jack, and vice versa? I assume you mean this because you've measured the channel imbalance of your source and found that it is opposite to the imbalance coming out of your C2A, and so your hypothesis is that the amp swaps left and right signals, thereby passing on the imbalance of your source. Do I have that correctly?

(I ask the above clarifying questions b/c in audio-speak the term "inverted" often refers to phase inversion - i.e., if you imagine a sine wave signal with a positive peak at time 1 and a negative peak at time 2, the inverted version of that sine wave would be flipped 180 degrees: a negative peak at time 1 and a positive peak at time 2. I don't think you are asking about phase inversion -- but please correct me if I am wrong).

Re whether left and right signals are  swapped: I'm pretty sure that none of BH's amps swap left and right signals b/c (a) that would significantly change the presentation of music (e.g., horns that should be on the left are instead on the right), and (b) I can't imagine any circuit design reason/benefit to swapping signal sides. I think the only way for the signals to get swapped is by user/builder wiring error - my guess would be at the attenuators. So you might want to double-check your signal wiring.

cheers, Derek

You've pretty Nailed what my intention for my Question was

I've tested if the Input signals could be swapped with a little test in the Speaker Configuration on the Operating System.
I've let for an example play only the Left Side and the Sound appears on the Left Side and vice versa, so It doesn't seems like that I have made an wiring mistake with the Left and Right Channel.

It was just a hypothesis as you have already stated

[Paul Birkeland]

The Crack and C2A are inverting, yes.

[Thermioniclife]

I apologize if my posts seemed rude. My sense of humor is often misunderstood. Rest assured that I will keep my trap shut.

[XforceVesa2]

I've made completely new Measurements as I got a new Source(RME ADI-2 DAC) and because I was just curious what measurements I get this Time.

First I measured the Source from the ADI 2 DAC and got the Following measurements:

L = 1,2136V

R = 1,2138V

So an "Imbalance" of 0.001424 dB, so basically a perfect Balanced Source

The next measurements I've made with Different Tube Setups.

The first measurements I've used as Input Tube The TAD 12AU7/ECC82 Tube and the Stock Tube from the Crack(6AS7) and got the following measurements(All of the Following measurements are made with my Normal Listening Volume):

L = 0,201V

R = 0,1903V

So an Imbalance of 0.5dB (RAW = 0.474923)


For the second measurement I've used as Input Tube the Stock Tube from the C2A(also a 12AU7/ECC82) and the Power Tube from the Crack(6AS7) and got this:

L = 0,186V

R = 0,172V

So an Imbalance of 0.7dB (RAW: 0.679647)


For the last Measurement I've used as Input Tube the TAD 12AU7/ECC82 Tube and the Stock Power Tube from the C2A(6080) and got this:

L = 0,205V

R = 0,1926V

So an Imbalance of 0.5dB (RAW = 0.541934 dB)

As I've said I did this measurements only because I was curious what would happen If I change the Source.

But I have only one Question, there's one thing I don't understand.
With my Old Source(Ifi Micro iDSD BL) I've got with my current Tube Setup(Input= TAD 12AU7/ECC82, Power = 6AS7(from Crack)) approximately an Imbalance of about 0.3dB( This Source had an Imbalance of about 0.2dB) but with my new Source(ADI-2 DAC(Perfectly Balanced)) and the same Tube Setup I've got an Imbalance of about 0.5dB.

So my Question is how is this even Possible as it seems to get "worse" with the new Source? 

[Paul Birkeland]

If the amp has a slight channel imbalance favoring one channel and your source has a slight channel imbalance favoring the other channel...

[Deke609]

Further to PB's point, I think you found the probable explanation some time ago:

I've got the Following measurements directly from the RCA Output from the iFi:

L = 1,434V

R = 1,463V

So an imbalance of about 0,2dB

The strange thing here is that it seems like that the right side is louder than the Left side before it goes trough the amp.

So it looks like the IFI imbalance and the C2A imbalance partially cancelled out.

It would be an interesting experiment to trace the signal balance through the C2A to see where the imbalance pops up. You've already done some of that by testing the voltages that come out of the attenuator. You got 1.06V out of one side, and 1.08V out of the other. I don't know anything about decibel calculations, but using the following equation I found online, dB difference = 20*log(V1/V2), suggests this you've got a 0.16dB difference. If this calculation is correct, that's part of your answer. PB could probably figure out (or maybe you could) what value of resistor to add in series or parallel at the attenuator to get closer to a zero difference between channels. I don't have a Two-Quiet, so I can't be of any help here.

This is all kind of academic since your hearing test results suggest you won't be able to hear the channel imbalance in any event, but it could be a fun thing to track down and solve.

cheers, Derek

[XforceVesa2]

Further to PB's point, I think you found the probable explanation some time ago:

So it looks like the IFI imbalance and the C2A imbalance partially cancelled out.

It would be an interesting experiment to trace the signal balance through the C2A to see where the imbalance pops up. You've already done some of that by testing the voltages that come out of the attenuator. You got 1.06V out of one side, and 1.08V out of the other. I don't know anything about decibel calculations, but using the following equation I found online, dB difference = 20*log(V1/V2), suggests this you've got a 0.16dB difference. If this calculation is correct, that's part of your answer. PB could probably figure out (or maybe you could) what value of resistor to add in series or parallel at the attenuator to get closer to a zero difference between channels. I don't have a Two-Quiet, so I can't be of any help here.

This is all kind of academic since your hearing test results suggest you won't be able to hear the channel imbalance in any event, but it could be a fun thing to track down and solve.

cheers, Derek

It's an interesting Idea but as It's only an Imbalance of 0.47 dB this step seems a little bit drastic as Paul has stated before


Just out of Curiosity what Channel Balance does the other Crack and C2A users on this Forum measure on their Headphone Jack?

[Paul Birkeland]

Just out of Curiosity what Channel Balance does the other Crack and C2A users on this Forum measure on their Headphone Jack?

You're the only one...

I did leave space in the layout to add feedback resistors, which would tighten up the channel balance.