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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
rolyasm OP
14 posts
 
So switching out the tubes didn't change the red light which stayed on in the V7 position, regardless of the tube placement. There are not other red lights or "fuse out" indicator lights on. I think I read something on another forum about a "plate fuse", but I can't be sure that was what was mentioned and I can't find the thread again. 
I will give a call to CJ tomorrow. I'm sure it will cost a fortune just to ship that beast. I see some upgrades on their page, anything you recommend if I send it in. 
As far as the SL6's, I think I will list them on here or on Ebay. I have enough speakers and if I keep the amp I will want to take that money and use it on a speaker set that matches the amp better, or to help offset any repair costs. Thanks again for all your advice. 
R
rolyasm OP
14 posts
 
OH damn. They are at the CES show all week. :(  Have to wait until next Monday to get any answers. 
jond's avatar
jond
5,794 posts
 
Hang in there R it's gonna all be worth it when you get that amp fixed up and singing.
jazzonthehudson's avatar
jazzonthehudson
277 posts
 
I am not a tube techie but judging from the symptoms described you may have a leaky coupling cap; usually 0.22mF 600V. If you call CJ, their engineer (Jeff) will probably ask you to ship it in for repair as you already did the swapping of the (EL34) tubes. Not sure where you live but if you were near NYC, I can recommend you some great tube repair shops as the CAV50 is pretty standard.

FWIW, I had the CAV50 for awhile in my library setup, if I remembered correctly it had the same or, at least similar, power stage design as the MV50. Not bad when you rolled the line stage tubes.

As for the SL6’s sound bright with the CAV50, did you try the speakers in another setup?
rolyasm OP
14 posts
 
Still waiting on a call from CJ. I went to a local shop ( UTAH) and they said CJ is a company that doesn't give out schematics so they can't work on it and I have to send it in. :(  The local owner recommended the Mullard EL34, and I have recommendations for the Genalex Gold Lion KT-77 and the JJ E34L. Is it really going to sound different with these different tubes, and if so, should I just roll the dice, or do any of you vets have experience with all three of these recommendations and can offer me some advice. Lastly, I think these tubes are all original and probably have never been replaced, although the amp has only been used less than 100 hours during that time. Do tubes degrade, and if so, should I just do a mass exchange of all the tubes? 
JAZZONTHEHUDSON: What do you mean by "rolling the line stage tubes"?
I did try the SL6's in a solid state setup, and they sounded fine. Not as good to me as the mid-to-hi-grade RBH I was comparing them to. But with a solid state and my record player, it was nice. Might keep them just for retro sake. 
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