old USA 12ax7's in Caliber 50+??

[drdowell]

Hi, I have tried putting some old USA tubes like Sylvania, GE, RCA in different preamp positions on my '92 Caliber 50+ head.
It sounds better but after a while it starts cutting out and signal/sound goes to 1/2 power or dies completely. I put new production tubes back in and the problem goes away. I've never had this happen with NP tubes like TAD/Shuaguang/Mesa etc

Is there some reason that the old USA tubes are flakey in these amps? Maybe the pins on the older ones don't align as well?

Can anyone else confirm trying this and having this problem?

thanks

 

[stokes]

You say "old" USA tubes.If by old you mean used,then I would have to say the tubes were at or very near the end of their useful lives.I have a lot of NOS preamp tubes,close to 100 in tube caddy's and have a dozen amps loaded with nothing but NOS or lightly used old stock tubes and have had no problems with preamp tube failures.I have seen more failures with current production tubes in repairs I've had in my shop.While its true that higher gain Boogie amps put more stress on preamp tubes,I still find the old stock tubes out last current production.

 

[Markedman]

It's not just tubes that were made better way back when. There is something magical about older electronic stuff from the 50's and 60's. Sure you've got convenience now a days, and the price of a T.V. is an all time low with the picture a lot better, but the sound of those early 60's amps with early 60's guitars is unearthly, it really is. The copper in the wires and the metal used in making the amp and the guitar's parts was superior to what is in my 2012 Les Paul I just got. Kinda disposable, rather than fixable technology. Peavey amps were very popular when I was growing up and they sounded great until you actually used them with a band. It didn't matter that it was 150 watts, it couldn't keep up with a 20 watt Marshall or an 18 watt Fender with new tubes. You could see the fellow's fingers flying a mile a minute but there was just mush coming from his amp. Old stuff can be 10X better.

 

[MrMarkIII]

Electronics manufacturing involves the use of dangerous substances, many of which cause environmental problems - caustic chemicals, acids, lead, and other stuff one generally doesn't want to eat, or find in one's tap water. You know, all that Erin Brockovich stuff. Chromium hexaflouride: it's not just for breakfast anymore.
If you can't use all that neat poison, the quality of the electronics goes down while the costs go up. **** that pesky EPA.
So, that's a big reason why new tubes ain't as good as old tubes. Even the cardboard in the tube boxes is better.
You just got lucky with some bad tubes. Been there. But you're just as likely to get a brand-new bad tube. Stuff happens.

 

[stokes]

Enviro issues is what drove production out of this country and into the eastern hemisphere.Tubes today are made with a built in obsolesence.In the old days everything used tubes all electronic technology revolved around tubes.There was a HUGE market.The biggest consumer of tubes was the military.They bought millions every year.In order to get a military contract you had to make tubes to a higher standard or you were out of business.All the major manufacturers built for the military.It wasnt cost effective to make better tubes for the military and re-tool to run a lesser or light duty tube for general consumers,so all tubes were made to military standards.Nowadays the market for tubes is miniscule,guitar amps and hi-fi enthusiasts only.In order to sell enough tubes to make production profitable they have to sell more tubes to less people than years ago.You'll never see current production tubes that last like the old RCA,Sylvania,etc.I've got a couple of Ampegs from the 60's with the original Bugle Boy pre-amp tubes still going strong.I have more than enough NOS preamps to change them,but they just dont need it yet.

 

[drdowell]

You say "old" USA tubes.If by old you mean used,then I would have to say the tubes were at or very near the end of their useful lives

The tubes that appeared to be causing the problem are fine when I put them another amp so I know they aren't at the end of their useful life. It doesn't make any sense to me, they seem to fit really well into the pin sockets, so I don't see how it could be an issue with the pins contacting the socket, I just thought maybe someone else had had this problem.
I've tried it two times with different USA tubes with the same result, then the tubes are fine when put in another amp. There is just some freaky coincidence going on here, I'll give it another go.

 

[stokes]

I have found that some tubes that exhibit excessive noise and microphonics in high gain amps will be fine in lower gain Fender type amps.The reason for this is that all preamp tubes have some degree of microphonics and noise.The higher gain circuits amplify these noises more than a lower gain circuit.But never the problem you describe.A tube that causes a loss in volume or cutting out is indicative of a weak tube.