Possible Channel Imbalance[Solved]

Yes, the LEDs on the low current board aren't biased with as much current as the high current boards.  The LEDs on the 9 pin socket also have more current flowing through them than the LEDs on the low current board, so all is normal.
 
I've just swapped the 12AU7 Input Tube from my Crackatwoa with my other 12AU7 Input Tube from my Crack but the Channel Imbalance doesn't Dissapear, does that means that I must have a bad solder joint somewhere in my Amp?


Edit: The Crack seems to also have a Channel Imblanace (Left is a little bit Louder than right but its better than on the Crackatwoa). I've noticed that the channel balance was a little bit better as I've used the Power Tube from the Crack(But that doesn't make any sense? )

Edit 2: I think If my Previous Amp the Crack and my new Amp the Crackatwoa shows the same Phenomen I think it's very unlikely that I've probably made the same mistake the second time(Left a little bit louder), and I think it's actually more depent on the Tubes I'm using(Stock Tubes from Crack and Crackatwoa) as you have stated earlier in this Thread.

Edit 3: I've made new Measuremtns directly from the Headphone Cable with two Volume Settings as at the start of this Thread.
I've swapped the Stock Tube from the Crackatwoa with the Stock Tube from the Crack(seems to be a 6AS7 instead of a 6080).

At my "Normal" listening Volume I've got this Time:

L = 0,22 V

R = 0,208 V

So an Imbalance of 0,5 dB

At the max setting(0dB) I've got

L = 11,85 V

R = 11,2 V

So an Imbalance of 0,5 dB

The Strange thing is that in my Opinion the Channel Balance with the Stock Tube from the Crack(6AS7) is a little Better than the Balance from the Stock Powertube(6080) from the Crackatwoa.
 
Since both amps show the same/similar imbalance when measuring from your headphone cable, you may want to rule out the cable as the cause of the problem.  I'd try measuring from the rca outputs themselves.  Alternatively, you could swap left and right cable plugs and see if the imbalance follows the cable.

cheers, Derek

 
I've mad new measurments on the Crackatwoa and it seems like that the Channel Imbalance is at every Volume setting at about 0,5dB.

I've also made new measurements on the Crack with different Volume settings and it seems like that the Channel Imbalance on the Crack is a lot lower than on the Crackatwoa(only about 0,2dB).

I don't know what causes this Imbalance on the Crackatwoa as all solder joints seems to be ok :/


Edit: The strange thing is if I plug the Input Tube from the Crack in the Crackatwoa the Channel Imbalance seems to be going worse(about 0,6dB)
 
Paul Birkeland said:
Are these measurements on the Crack-a-two-a without headphones plugged in?  If not, do be sure to give that a try too.
Click to expand...

The Headphone wasn't plugged in during the measurements(Only the cable as the Headphone is detachable from the Headphone cable)
 
I don't think I know any mastering engineers who can hear a .2dB differential. The average listener can typically make out 3dB, a practiced audiophile can maybe hear 1dB. Best I've ever seen measured was my old partner Paul Stubblebine who could make out .25dB. I used to be able to discern about .5dB. Don't know if I could these days.
 
The thing is before I made these measurements, I've noticed the Imbalance while I heard music.

Later I've checked the Balance with a Stereo Perception Test from Audiocheck.net, they used a monoraul Recording of someone Knocking on the Door.

I could easily hear that the Left Side was louder than the right side, I've turned the Headphone around and heard clearly that this time the right side was Louder than the Left Side.

After that I decided to take measurements directly from the plugged in Headphone cable and could see that the left side has a little more Voltage than the right Side and that the Imbalance I've measured is around 0.5 dB :/
 
Paul Birkeland said:
You could try swapping the red and white wires at the headphone jack.
Click to expand...

If you determine that the cable is not the source of the imbalance (i.e., slightly higher impedance on the right channel than on the left), is there any possibility that the imbalance is coming from your source?  I could see this being the case if, for example, you were using your phone or computer as both your music source and the source of your test tone for taking voltage output measurements.

If the amp is in fact producing the imbalance, maybe some Kaiju-style PEC trimmer pots would be the way to go. Alternatively, maybe PB could figure what small resistor value is needed to knock down the left channel input and you could add that in series with the left signal volume pot wiring.

cheers, Derek
 
Deke609 said:
If you determine that the cable is not the source of the imbalance (i.e., slightly higher impedance on the right channel than on the left), is there any possibility that the imbalance is coming from your source?  I could see this being the case if, for example, you were using your phone or computer as both your music source and the source of your test tone for taking voltage output measurements.

If the amp is in fact producing the imbalance, maybe some Kaiju-style PEC trimmer pots would be the way to go. Alternatively, maybe PB could figure what small resistor value is needed to knock down the left channel input and you could add that in series with the left signal volume pot wiring.

cheers, Derek
Click to expand...

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?
 
I've took a new measurement this time Directly on the contacts U6 (Red whire) and U15 (White Wire) and got the following measurements:

Normal Listening Level:

White Wire = 0,22V

Red Wire = 0,209V

So an Imbalance of 0,5 dB(RAW Value = 0.445267)


At max Setting(0dB)

White Wire = 11,92V

Red Wire = 11,25V

So an Imbalance of 0,5dB(RAW Value = 0.502019)


From this contacts there goes a capacitor to the High Current Boards(I think the capacitator is there to decouple the AC Voltage from the DC Voltage?), could the Imbalance have something to do with the socket for the Shunt Tube or the High Current Board?(For the Red Wire, Right Channel)

Edit: I can't find any problem on the Shunt Socket and the High Current Board(Fort the Right channel, Red Wire) :/
 
Paul Birkeland said:
You could pull the shunt regulator tubes out completely and you'd most likely find no change in the channel balance.
Click to expand...

As I can't find the cause of this Imbalance do you think it could help if I buy a 12AU7 from an seller that states thats an Balanced Matched Tube?

Like this one? : https://www.tubeampdoctor.com/en/12au7a/ecc82-tad-premium-selected-balanced
 
I've purchased one.

I hope that it could be a solution to this problem.

I report when I get my hands on this Tube and do a new measurement.
 
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