[cyto]

Yesterday I noticed that the left channel was slightly louder than the right ( I just completed a Cornet 2 a few days ago). Swapping cables pointed to the Cornet 2 so I plugged my Musical Fidelity phono pre back in and balance was restored. Putting the Cornet 2 back in brought back the unbalanced sound.

Just for the heck of it I swapped the 12AX7 tubes around for each other and now both speakers are at the same level again.   But now I have a louder hum, the hum is the same level with or without the inputs from the turntable connected.

Both tubes are new Tungsol reissue 12AX7 from AES.

Any ideas?

Thanks

David

[galyons]

One of the tubes was likely not well seated in the socket.  Swapping them probably solved the problem,  Swap them back to double check.

Cheers,
Geary

[cyto]

One of the tubes was likely not well seated in the socket.  Swapping them probably solved the problem,  Swap them back to double check.

I thought about the seating but the hum level is now too high and plugging/unplugging the inputs from the turntable doesn't change it, I will play with it more tomorrow evening

[galyons]

Reflow the solder on both tube sockets. Sounds like a cold solder/ broken solder joint.

Cheers,
Geary

[cyto]

I reflowed the solder joints on the tubes. The channels are equal now (as they were after switching tubes) but I have a loud hiss.

I read in another thread that you should hear a hiss with nothing connected to the input and that the volume of that hiss should drop when you connect the turntable/cartridge.

Connecting or disconnecting the turntable does not change the hiss.

[cyto]

I swapped the 12AX7's back to their original positions and the hum/hiss went back to normal and the balance is still normal.

I think Geary was probably right about the solder joint causing the channel imbalance.

I wonder if one of the 12AX7's has an issue? Why else would swapping positions cause hiss?

Anyway I am going to get some more tubes for rolling and see how it plays out.

thanks guys 

[galyons]

If the hiss follows the tube, than the tube is likely the issue.  If I am understanding correctly, this is not happening.  One tube/socket combination yields hiss, switching the tubes giving the alternative tube/socket combination does not.  Carefully check the pins on the "hissing" tube for cleanliness, straightness, etc.  A different pair of tubes would be helpful to identify or eliminate a tube as the issue.

Do you have a DMM that measures frequency?  If so measure the frequency of the hiss at the outputs.  Hiss is much higher frequency than hum.  60Hz hum is grounding issues, 120Hz hum is transformer.  Much higher frequency hiss is most likely the tube.

Cheers,
Geary

[cyto]

Do you have a DMM that measures frequency?  If so measure the frequency of the hiss at the outputs.  Hiss is much higher frequency than hum.  60Hz hum is grounding issues, 120Hz hum is transformer.  Much higher frequency hiss is most likely the tube.

Cheers,
Geary

Yes my DMM does read frequency, thanks for the suggestion!

[cyto]

It is 60hz, really not that bad now. I can live with it but I know I will try to reduce it for the same reasons people climb mountains...

Will grounding the transformer to the star ground reduce this?

[cyto]

I fixed the 60hz hum
I was using the TT ground for a star ground. I put a new star ground in close to the power plug and I added a little more shielding between the power wires and signal wires. The hum is almost imperceptible at normal volumes.

The sound quality I am getting now is awesome.

[galyons]

Congratulations!  The C2 is a joy and a value well beyond it's cost.

Cheers,
Geary