Possible Channel Imbalance[Solved]

[Paul Birkeland]

Could the Channel Imbalance have something to do with the Large PC Board as stated above?

What Channel Imbalance does the Crackatwoa normally have?

Are these Values that I have measured at the begin at this Thread a imbalance that normally Occur at this Amp?

A problem like this is usually either a solder joint that isn't 100%, or just a bit of tube imbalance (in the 12AU7).

As I mentioned before, channel balance is far more tube dependent than circuit dependent.  Creating a spec for channel balance would require a sample of maybe 100 12AU7s to give an average expected channel balance along with the distribution of what was actually measured.  This is one consequence of not having global feedback, if we put feedback around the amp I could make the channel balance less than 1/4 of a dB pretty easily.

Could the Channel Imbalance have something to do with the Large PC Board as stated above?

Which board is the large board?  Can you post a photo of what you're seeing?

[grufti]

I was and I still am in a rush. Sorry. Plan can be adapted to the Crackatwoa, skip the attenuation, set the volume control to a couple of different points, three or so, alternate channels at each setting.

I suggested buying another one or three reasonably priced 12AU7 tubes because the amplification factor of the Crackatwoa depends on that a lot.

[XforceVesa2]

As I mentioned before, channel balance is far more tube dependent than circuit dependent.  Creating a spec for channel balance would require a sample of maybe 100 12AU7s to give an average expected channel balance along with the distribution of what was actually measured.  This is one consequence of not having global feedback, if we put feedback around the amp I could make the channel balance less than 1/4 of a dB pretty easily.
Which board is the large board?  Can you post a photo of what you're seeing?

Ok I think I now understand what you meant

I have again took an Inspection of the Socket from the Input tube and couldn't find a problem.
The solder joints seemed fine, I have measured the impedance from one solder joint to another end e.g hold one probe of the multimeter against one pin and the other probe at the other end of the soldered wire, my reading was 0.00 Ohms, also the two LEDs on the Input socket lit bright when the amp is On.

I've meant the Low Current C4S Board.

I don't have a problem with the slight channel imbalance I was just worried that I've could made a mistake in the circuit and thats what I just wanted to be sure that there's no mistake in my cicruit
If the channel Imbalance comes from the Tube then I can live with that.

[Paul Birkeland]

If you have a large difference in LED brightness on the center low current C4S board, that would tend to indicate a possible soldering problem. 

[XforceVesa2]

I have uploaded 4 Pictures that shows the different leds on the circuit.

I've meant that all the LEDs in the Amp seems to lit equally except the LEDs on the Low Current Board(the four LEDs on this boards are equally less lit than the other LEDs in the Amp).

I hope that the pictures shows it better than what I try to explain what I mean(Its not my native language) 

[Paul Birkeland]

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.

[XforceVesa2]

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.

[Paul Birkeland]

There is some opportunity for channel imbalance to creep in from the 6080, but it's less likely in my opinion. 

[Deke609]

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

[XforceVesa2]

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]

Are these measurements on the Crack-a-two-a without headphones plugged in?  If not, do be sure to give that a try too.

[XforceVesa2]

Are these measurements on the Crack-a-two-a without headphones plugged in?  If not, do be sure to give that a try too.

The Headphone wasn't plugged in during the measurements(Only the cable as the Headphone is detachable from the Headphone cable)

[Doc B.]

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.

[XforceVesa2]

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]

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