Tube Crisis!

[Meshuggahnans]

So I  looked in the back of my amp today, looking for something and I noticed that one of my power tubes wasn't glowing.  From previously overhearing a guitar tech when my friend had a similar problem, I KNOW that I shouldn't play it until it is fixed.




Here is some good information I found on my amp from a completed listing on ebay:

http://cgi.ebay.com/Vintage-Acoustic-Co ... dZViewItem

According to that, it uses "It uses 4-6L6's and five 12AX7's."  but I only obviously see 4.  So I assume I'm looking at the 6L6's.

So my questions are:

1 - Do I have to replace all of the 4, or just the one?  And if just the one -- does it have to be identicle brand etc...
2 - What are good 6L6 brands?
3 - I heard you have to "re-bias" and amp when you switch tubes.  What is this and can I do it myself?
4 - ...can I swap them myself without being the first offsetguitars member to die?

[RumorsOFsurF]

1 - Do I have to replace all of the 4, or just the one?  And if just the one -- does it have to be identicle brand etc...

No, you can replace one at a time.  You should check them all, though.  You can get matched quartets, though.  Those are generally your best bet.

2 - What are good 6L6 brands?

If you ask 5 people, you will likely get  5 different answers.  My opinion is that you can't go wrong with JJ's.  NOS tubes are totally unnecessary, and just hype.  Don't buy Groove Tubes, as they are just re-branded garbage.

3 - I heard you have to "re-bias" and amp when you switch tubes.  What is this and can I do it myself?

If you replace power tubes(6L6's) you will need to rebias.  I'm not familiar with how to do it, so I take it to a qualified tech.
There's a guide Here, but it's pretty specific to a Hot Rod Deluxe.  It may give you an idea.

You can swap preamp(12A*7) tubes freely without worrying about bias.

4 - ...can I swap them myself without being the first offsetguitars member to die?

Use extreme caution when messing about with tube amps!  The capacitors hold a huge charge.  You can swap tubes easily, though.

[Stereordinary]

All of the best tube amp technicians that I have ever talked to told me that you don't have to re-bias your amp everytime you replace the power tubes.  It's probably a good idea, but if you can't afford it, just swap out the one tube and play through the amp.  If it sounds fine, you're done.  Just consider saving up some dough and getting the thing properly serviced later.  If it doesn't sound good on the other hand, you may need more than a re-bias.  New caps and a general cleaning, that sort of thing.

[Jay]

2 - What are good 6L6 brands?

If you ask 5 people, you will likely get  5 different answers.  My opinion is that you can't go wrong with JJ's.  NOS tubes are totally unnecessary, and just hype.  Don't buy Groove Tubes, as they are just re-branded garbage.

This isn't necessarily accurate.  Groove Tubes rebrand stuff that isn't junk too.  In other you can buy European and Russian tubes from them as well as Chinese junkers.  The real reason to avoid them IMO is because they're charging a premium price for matching and silk screening their nice logo on the glass.