Possible Channel Imbalance[Solved]

[Deke609]

You could try swapping the red and white wires at the headphone jack.

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

[XforceVesa2]

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

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?

[XforceVesa2]

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]

You could pull the shunt regulator tubes out completely and you'd most likely find no change in the channel balance.

[XforceVesa2]

You could pull the shunt regulator tubes out completely and you'd most likely find no change in the channel balance.

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

[Paul Birkeland]

It is certainly an option and could provide useful data.

[XforceVesa2]

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.

[XforceVesa2]

When I got the new input Tube and the Balance didn't get better what measurements or checks could I also do?

[Paul Birkeland]

That was quick, you were able to buy a balance tested 12AU7 in 2 hours?

[XforceVesa2]

That was quick, you were able to buy a balance tested 12AU7 in 2 hours?

It was more Like an what if? Question 

[Thermioniclife]

Holy smokes, take a chill pill, smoke a bowl or have a drink and relax.

[XforceVesa2]

Holy smokes, take a chill pill, smoke a bowl or have a drink and relax.

Yeah, I think you're right. I'm a little bit impatient at the moment. Sorry for that.

I 'll report as stated above when my new Tube arrives and if this change something or not.

[Paul Birkeland]

Oh, I didn't understand that. 

Let us know what happens when it arrives.

-PB

[XforceVesa2]

Sooo I've got my new 12AU7A/ECC82 Input Tube today and got the Following Measurements:

At my "Normal" Listening Volume I've got the Following Measurements:

L = 0,239 V

R = 0,23 V

So an Imbalance of 0,3dB(RAW Value 0.333147)

I've done this time another measurement with The Volume set a little bit quieter than my Normal Listening Volume and got the following measurements:

L = 0,169 V

R= 0,163 V

So an Imbalance of 0,3dB(RAW Value 0.3139)

And the last measurement at max Volume:

L = 12,29 V

R = 12,15 V

So an Imbalance of only 0,1dB(RAW Value 0.099318) :O

If I compare this measurements with my first measurement it seems like that the Channel is now more in balance(The Imbalance is now more harder to hear).

It seems like that the possible cause of this "Issue" come from the Stock 12AU7.

The new 12AU7A/ECC82 was a little more expensive and the shop has stated that this Tube had an Balanced Output Test.

Is it normal that the Imbalance got fewer as I turn up the Volume even with the Twoquiet Stepped Attenuator as the measurements indicate?

[Paul Birkeland]

What's the channel balance of your source?