Tube flash

I'm not a CJ expert (in fact I've never owned one) but as I recall the CJ Premier 12 was originally designed around a 6550 tube, not an EL34. It also has a manual bias system where you turn a pot until a LED turns on. If I'm correct so far read on....

Amps of this type come with a bias arrangement that anticipates the use of certain tubes which would exclude others. For example many, if not most, will bias 6550's at around 50ma. But smaller tubes such as an EL34, E34L or 6l6 and 6l6 GC performs optimally at a much lower number, ranging from 25ma to 35ma (for example the latter for the E34L and the lower numbers for EL34s which would be around 30ma). This is general and amps/tubes will be different considering amps design and the extent that you select the bias and are willing to lower or increase bias to get the best tone, etc.

If your amp has a bias circuit which assumes 6550 type power tubes, as well as KT88s and KT90's, then you would be biasing your EL34's far to hot. This would cause early death, shorting, etc.

I do not know how you could circumvent this unless you could manually bias the tubes using a meter with real numbers or by getting CJ (or a good techie) to alter the bias arrangement so that when properly biased according to the LED your bias will match the requirements of smaller power tubes.

I hope that helps you a bit. I may be way off base.....:-)

PS

BTW when you read Jim McShane' post of AA (posted above by Jea48) be sure to read it in context, not just superficially by looking at the words 'bad' and the yellow highlighting. McShane has always spoken highly of SED EL34's and that has not changed, although he recently indicated he had recieved some negative comments on NEW SED 6550's which suggests a new quality control propblem.

Jaffeassc, "so I assume...." You know what they say about what happens when you assume........:-)

Next time you talk to CJ ask them what the bias setting programed into the amp actually is. After they tell you ask them what the bias setting is in the 6550 model. Then find out if they actually checked the bias in your amps with your tubes in it as opposed to just noting the the tubes and the little LED were working.

BTW, some tube amp are designed to push their tubes very hard to meet high power spec's. Yours may just be one of those and underly the reason for CJ's statement about it having problems with a speaker that required more current, current their amp couldn't deliver.

BTW I drove Quad 63's with SED EL34 in a SFS 80 amp which only put out 40wts with this tube. I set the bias at 30ma and drove them off a 3.5ohm tap (internally configured). I never had a problem with tube reliability or tube life and I drove them hard enuf that they 'rattled' a tiny bit.

CJ's comments about the 63's could be accurate about their needs but I really don't under why a high quality mono amp couldn't drive them. As I recall they have a minimum impedance of about 3.5 ohms in the bass - any respectable tube amp should be able to handle that, especially a Quad which you can't drive that hard anyway. Since you have the same problem with dynamic speakers I suspect the CJ's may have a problem. If you have a techie nearby you might ask him to check and see what the bias actually is.

But, as I said in my first post I'm not a CJ authority.