Tube flash

Rodman, funny you should mention Upscale because that’s where these tubes were purchased. I guess it’s the luck of the draw, and in my case, my draw was aces over sevens.

And Newbee, you have an interesting premise. I should have mentioned though that my amps are the Premier 12 XS, which are configured to use EL34’s. So I assume the bias circuit is designed around EL34’s, but I’m going to ask Conrad Johnson that exact question. It’s also interesting that the last time I was at Conrad Johnson, I bumped into Lew Johnson and asked him what he though might be going on. His first question was what type of speakers are you using. When I told him Quads (63’s), he commented that they (Conrad Johnson) had some previous problems with customers that used Quads and their amps. He said that the Quads, under certain circumstances might draw too much current. This all sounded a little strange to me (I was always told Quads and tubes were a good match) but I’m not an electrical engineer and he was talking a little over my head, so I may have misunderstood. Since then I’ve taken the Quads out of service, and I’m using dynamic speakers. But the problem has continued.

Thanks again for everyone’s comments. Any other thoughts would be very much appreciated

Mr J- How old was the tube that failed? Have you contacted Kevin in regards to the tube's failure(and possible warranty)? Did the same thing happen more than once? You mentioned, "the problem has continued"(why I ask).

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.

I've had tubes flash, cause damage, and not only measure perfectly fine, but go on and lead a typical, long, quiet suburban life.

Culling tubes that test poorly in their infancy is certainly wise practice. While tubes that get through boot camp obviously will lend a higher degree of confidence, let's not be lulled into a false sense of security. Tubes do hiccup and fail, and sometimes collateral damage results. The old investment adage "past performance is no indication of future results" rings true with vacuum tubes as well.

"How old was the tube that failed? Have you contacted Kevin in regards to the tube's failure (and possible warranty)? Did the same thing happen more than once? You mentioned, "the problem has continued”

No I haven’t contacted Upscale…the first tube that failed was probably 4 – 6 months old. As I mentioned before, this is the fourth of eight tubes that has failed. I should have taken notes, so I really don’t remember when the tubes failed, which positions failed, etc. I do know it has happened in both amps.

"(why I ask)".

“Why” the problem continues is what I am wondering as well.

"Next time you talk to CJ ask them what the bias setting programmed 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 tubes and the little LED were working."

Now that I know a little more specifically what to ask, I will. Thanks for the advice. I do know that they checked the bias in the amps with my tubes the last time they were in for service. That’s how they found the problem (the amp was blowing fuses and my tester was not detecting a bad tube).

"If you have a techie nearby you might ask him to check and see what the bias actually is."

Actually, Bill Thalmann, whom I believe may have designed the Premier 12’s when he worked for CJ, also has his shop in my area. So I may take it to him the next time it happens.