[starkiller]

Well, finally got some time to listen to my new speakers and tube amp and wouldn't ya know it, a problem    There is a definite channel imbalance.

Swapped out the preamp/amp cables and the the problem went to the other speaker. I am thinking its the preamp.  Its a hybrid and when I turn it off there is noise that comes from the sub. It makes noise also when i turn it back on but its louder then when turning off.  This is with the volume control all the way down, the sub is self powered. The preamp is being used to feed the mains and the sub.

Before I remove the top of the preamp and starting swapping tubes are there any other options??

thanks!

[JakeJ]

You swapped the right and left interconnects between preamp and amp at the amp or preamp end only, is this correct? If so, and the problem swapped with the change, then it is likely it's the preamp.  Do you have another set of I/Cs to make sure it isn't the cables themselves?  Also did you try the experiment with more than one source?  Just trying to think of all possibilities before opening up the preamp.

Is it a tube preamp?  If so, can you try swapping tubes to see if they are the culprit?

That's all I can think of at the moment.  Hope it helps.

JakeJ

[starkiller]

It happened on all sources.  So, opened up the amp, swapped out the two inner differential input tubes with different ones, fired up a disc, bass!!  I've got bass!  And the imbalance was gone. Repeated the same song a couple of times to make sure everything stayed the same...about halfway through the third time the bass dropped, alot.  Imbalance was still gone though.  Hmm, swapped out the two outer buffer tubes with new tubes, bass is back!  Now have gone through about 7 repeats of the same song and the bass is there and the imbalance is still gone.

Could all of that been caused by the tubes??

[JakeJ]

Yes but I find it highly unlikely you would experience back-to-back tube failures, however not impossible.

In your last post you said you "opened up the amp", in your first post you seemed to think it was the preamp.  What happened to make you change your mind to determine it was the amp and not the preamp?  Make and model of both please!  Also the tubes in question.

Regardless of my curiosity, you seem to have troubleshot your own problem and I commend you for that!  No small feat, sir, be proud!

Regards,
JakeJ

[starkiller]

Geez, I need to preview my posts alot better   I meant to say i opened the preamp, not amp.  Preamp is the Valve Audio Black Widow with the 6DJ8/6922 variants.  The amp is a custom Niteshade.

Yeah, it  does seem strange but will keep the top off the Black Widow for a few days just to make sure the problem is solved

[Niteshade]

Is the preamp well ventilated?

[starkiller]

yep, all by its lonesome on the shelf with a good 9" of airspace above it...

[JakeJ]

Mmmm...nice.  It may have to do with the fact that the output is direct coupled, i.e. no output coupling capacitors.  The circuit may push the tubes used a bit harder thus requiring high quality tubes.

Note that this is all conjecture on my part.  Also please note that my "Mmmm...nice" reference is for the attractive female pictured lying in the grass on Valve Audio's website.  No other valuable info there.

Keep us posted, starkiller.

JakeJ

[starkiller]

Yeah, nice website with not much info, you should see the owners manual..its worse

Strange with the tubes as I was using the ones he recommended.  So, with new, different brand in it I will see what happens.