2. amps-preamps
  3. 119241-73122

Conrad Johnson CAV 50

Just acquired this beauty from my father in law. I've never owned a tube amp, so not sure if I should sell it, or keep it and pay him. Anyway, a question for you tube heads. One of the EL34 tubes in slot V7 ( a tube which can have it's bias adjusted, which I assume means the power transmitted) has it's red light constantly on. I turned the bias all the way down and it still flickers. However, I noticed that my left speaker sounded blown/distorted. When I turned the bias up, the distortion decreased. The instructions say to turn the bias down/counter clockwise, until the red light goes out. But, if I do this, it sounds bad. So, my question is this. Is it simply a tube I need to replace to fix that problem, and if I change one tube, should I change them all. Next question is I searched for the EL34 tubes and of course there are a large variety of them. Any thoughts. To me the amp sounds little bright with the Celstion SL6's I am using, so any warmer tubes would be nice. Also, if I were to sell this setup, any idea on what I might ask on pricing? Thanks.
Roly
rolyasm
yogiboy's avatar
yogiboy
5,658 posts
 
Just swap the left and right channel tubes. If the trouble moves to the right channel then you will know it is a bad power tube. New EL34 tubes are only about 15 bucks each. I have used JJ EL34L power amp tubes and found them very nice. If you want to retube that amp, take a look at the Tube Depot site . BTW,I think the preamp tubes are the more important choice when choosing tubes. Keep that Amp!
bbroussard
188 posts
 
It's a keeper.  You might need to re-tube.
tls49's avatar
tls49
1,351 posts
 
I don't disagree that it's a nice integrated, however the SL6 is the wrong speaker to use with it. The SL6 is a power hungry, inefficient speaker that needs high current SS.
jond's avatar
jond
5,794 posts
 
tls49 you're right just looked at the specs for the SL6, that's probably also why the OP is perceiving the sound as bright.
rolyasm OP
14 posts
 
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
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