Conrad Johnson CAV 50

Thanks for the replies. I changed the power tubes (EL34) to the opposite sides and the problem persists. It might even be that the distortion can be eliminated by having the bias all the way up and having the red light solid constantly, but I am worried this may be bad for the amp. Any other suggestions? I tried another speaker, a cheap one that I assume is easier to push, and it doesn't change the problem, so I am guessing it is not related to the speaker being to difficult to push, but an amp problem. 
TLS49, from what I have read, you are totally correct about he SL6's. It is interesting that when he bought this setup years ago at a high end hi-fi shop, this setup is what they recommended. Part of the reason I was thinking of selling this combo is it just doesn't sound good, but now I realize it is probably just the speakers being mismatched with a low power amp. Thanks for confirming that. 
Jond: I don't think he has ever changed the tubes. Although he has probably only had the amp on maybe 100 hours over the last 10 years. So the tubes probably just all need to be changed, unless time doesn't affect them, and only usage. 
Thanks for your ideas. If you have any more about where to proceed with the bias light, or whether I should even worry about it, all is welcome. Thanks for your time.
R

Roly you may also have another issue if it persists in both channels, perhaps a blown resistor or leaking capacitor, hopefully almarg or one of our more tech minded members will chime in with a better diagnosis. Or you can always simply call or email C-j on Monday. Either way good luck!

Sorry that should read if it persists in that one channel after flipping power tubes. Perhaps an issue with the bias circuit even?

I changed the power tubes (EL34) to the opposite sides and the problem persists.

Did the problem stay on V7 or did it move to the other side? If it stayed on V7, the amp may need to be looked at by a technician. If a tube cannot be biased properly, that should be corrected. Playing it long term will definitely not be good for the tube and if a defective part of the amp is causing the problem, that could affect other parts in the amp as well.

Even if the amp is working properly with new power tubes, it still won't be able to get maximum performance from the SL6. 

Roly ,

It sounds like your left channel fuse protection has blown.

The fuse protector are located on each side of the amp between the far left and far right EL34 and the 6SN7 tubes. You will see there are "fuse out" indicators next to the fuse protection. If it is lit red then you have a blown fuse. You will need a Buss Fuse  BBS-3/4

If the fuse out light is red , power down the amp and just unscrew the black knob and the fuse will come out with the knob. This will also mean the one of your EL34 tubes have gone bad , so you will need to replace both left channel tubes , or you will keep blowing fuses.