6L6GC from TubeDepot, PSA and questions.

[Kindly Killer]

I got 3 bad pairs of JJ's in a row. It took me a while to figure out what was going on because I am just learning amp troubleshooting, but I got 3 pairs in a row - the last two with the extra burn-in service, which I figured was an extra safeguard against duds - all three pairs went bad within 20 hours of playing time, in two different amps, causing stress on gigs and damaging my amp. Also I suspect it was a setback to my learning because I ruled out the tubes as the problem the second time. Three pairs doesn't comprise a random sample, but it seems like the odds of getting 3 bad pairs from a pool of tubes with very few bad pairs... unlikely. Anyway, I for one will be looking for better prospects, which is why I'm here.

First of all, TubeDepot seems like a good outfit. Does anyone have any advice/hookups to get satisfaction on these bad tubes? I really can't afford to keep antagonizing bandleaders, much less throw away money on bad tubes and days on amp repair. I think I don't really know the world of tube amps enough to know what is reasonable to expect. Do you guys just get lots of duds and expect more? Do you call up customer service in an inconsolable fit, demanding they come to your house and work off the debt as indentured servants?

Next, what are some better bets for reliability? What would be a good recommendation if each the following was my second criterion, after reliability:

• reliability - only one criterion. what's the gold standard for reliability?
• beautiful, detailed timbre
• volume/headroom
• value. not cheapness but value for what you pay. i don't mind paying more for more value, but i don't pay for features with no musical/practical implications. e.g. the only vintage stuff I own is stuff that's very hard to reproduce, e.g. pickups with obsolete magnets, pedals with obsolete chips, etc...
• good compromise between all criteria?

Finally, is TubeDepot a good source for tubes in your experience?

All answers to any questions are appreciated.

Thanks!
Michael

[tedmich]

they sell like 15 types of 6L6s what did you buy? People like the Winged C SED which cost almost 2X the new Tung-Sol which cost almost 2x the JJs.

So its JJs for me!

I'd have the amps bias checked, there is no way a non faulty tube should fail that quickly, and try the JJs

[Kindly Killer]

Whoops JJ's is what I got 3 bad pairs of. Maybe the tube itself is not the problem?

But why can I use POS Sovtek 6L6WXT+ for 4 hours per day, week after week, with no problems? I don't like the sound or headroom of those, but that's all I have that doesn't crash the amp, and I don't want to spend more time and money blindly.

[tedmich]

I should have read more closely...could be a bad batch but you need to be sure its not your amp killing them. Is your amp biased? Thats the only real variable I know which can greatly shorten good tube life. All things being equal (or cathode biased or non-adjustable bias amps) the problem is the tubes if one brand lives and one dies. I have not heard of any similar JJ horror stories but it could be a bad batch. If the pretested/burned in tubes similarly died your amp may be a specific killer of this particular tube. I'd get another well loved brand, say Tung-Sol 6l6, put it in and take straight to tech to check bias, if its AOK it was probably bad tubes and you'll have a fine time.

How did tubes "die"?

[Jazz P Bass]

[QUOTE=Kindly Killer;332242]Whoops JJ's is what I got 3 bad pairs of. Maybe the tube itself is not the problem?

But why can I use POS Sovtek 6L6WXT+ QUOTE]

I find the WXT's to be pretty darn good tubes.

Out of the box, most of them run hot, bias wise.
So you do need to check that.

[big_teee]

I had bad luck with JJ.
I have been using new sensor, and TAD tubes.
T

[Kindly Killer]

Thanks for all answers.

To answer questions: two tubes shorted, burning up resistors and caps in my Hot Rod Deluxe, the fuse in which is ineffective to protect components in the power section (still curious about figuring that out - ideally I'd like to be able to just change tubes when one goes bad). Third set failed in my Hot Rod Deville, which worked fine with another set of tubes, so I didn't investigate what went wrong, beyond "JJ's stabbed me in the back again". I know - just play the DeVille, which sounds better for parts, anyway, but I like the Deluxe much better when I'm on melody a lot, which is all of these 4 hour casuals.

Biasing: in both amps I biased the JJ's to where the test point reads 70mV. They sounded perfect for me but didn't last. When I put in the WXT+ (came with one of the amps) I set bias to get the same reading at the test point, and my headroom went to hell and I didn't like the sound of the overdrive. This time I set it to read 62mV at the test point, but I don't have another show now until Friday, and I practice with a fake master volume pot in the effects loop at very low volume, so it's hard to say how that tube set is going to sound now. I will give my ears another chance with the WXT+.

[Jazz P Bass]

70mv's bias is pretty hard on 6L6 tubes at the B+ that Fender's run at. (that's more in line with EL34's)

Try to keep in mind the fact that Leo ran tubes a heck of a lot colder than that. (25 per tube)

[kg]

honestly i don't really understand the attraction of running AB push pull stages hot. the tubes WILL wear out faster, and if i hear any difference at all it is usually the extra current draw making the sound mushier and less distinct.

you don't idle your car at 3000 rpms, do you? even if you have a 7k rpm redline? no, you set the idle rpm to be high enough to spin the accessories up (power steering/alternator/ac compressor/etc) and to keep a steady rpm, and that's it.

cliff notes: i like a cold bias.