Swapping tubes live question

cragginshrd

cragginshrd

Active member
I'm always worried about a tube going down live. I usually take a Fractal a s a back up. Curious the best method to find out if it's a pre or power amp tube? Also can the amp survive the night and still sound ok swapping one power tube without a bias for the night?
 
With the two amps I primarily gig, I can pull a pair and limp by on 50w if I have to, adjusting the impedance accordingly. That's the plan if I ever lose a power tube at a gig. I think part of it depends on how gracefully the tube dies. I think I'd prefer to leave the socket empty until I can give the amp a closer look.

If you know the tube layout you can sometimes pinpoint a preamp tube failure pretty quickly depending on which channels or functions are affected. Our other guitarist blew the tube that fed his effects loops, so that was pretty easy to isolate and replace.

Honestly though, if I have a tube/fuse failure at a gig, I'm going with my backup. My Axe-FX III is what I use for effects in the loop of my amp, and I can switch to that with an FOH feed in a pinch. If I have a power tube or fuse issue at a gig, I'll probably want to look at that a little harder before I replace them.
 
I always bring a handful of spare tubes to a gig, but there's not much chance of being able to diagnose any issues until I was between sets. I think you'd have to know your amp well enough to get a sense of what's wrong. If I had to narrow it down quickly (on a dark stage), I'd check to see if it was a channel issue (indicating a preamp tube), or a global issue. Then check to see if any tubes weren't lighting up or had gone dark. Beyond that, I'd try something in the loop to see if was a pre or power section issue.

That said ... 99% I'd just swap to my backup amp and go. I always bring a Bluguitar Amp 1 with me, set up to sound similar to my main amp. My board is already setup to switch channels on it the same way, so I'd just swap cables and be good to go. I rehearse with it so I'm just as comfortable using it or the main amp.
 
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From back in ‘the day’ to my most recent lil’ for fun shows, I always had a pair of heads on my cab. And if my #1 head took a dump, I was a speaker cable and a standby switch away from playing on. Only happened 2 or 3 times total, but dam glad to have my backup box of glass glowing and ready. Several folks who saw 2 heads often asked if I was slaving one into a load or running my FX in stereo.
 
Troubleshooting a tube amp issue during a gig is not recommended. If there's a problem, there's plenty of things it could be other than a tube. Even if you found the culprit, swapping in a known good replacement may or may not fix the issue at all, or for very long.

Having a small backup - even if it's just preamp type pedal that can feed a cab or PA - is a far, far better option to have on hand than attempting in situ amp fixes.
 
I look back on my prime gigging years from 24 to 35 and realized I never once had a backup amp or guitar at a show. Never broke a string, never had a cable or pedal failure. It never really occurred to me to have those things (backups) as I’d also never had a piece of gear fail at rehearsals either. I guess being that I was using 100 watt half stacks, sometimes full stacks, the thought of lugging more gear was being shut down by my subconscious..lol

I must have had the smoothest bridge saddles in all of the West Coast and didn’t even know it. 😂
 
skoora said:
I look back on my prime gigging years from 24 to 35 and realized I never once had a backup amp or guitar at a show. Never broke a string, never had a cable or pedal failure. It never really occurred to me to have those things (backups) as I’d also never had a piece of gear fail at rehearsals either. I guess being that I was using 100 watt half stacks, sometimes full stacks, the thought of lugging more gear was being shut down by my subconscious..lol

I must have had the smoothest bridge saddles in all of the West Coast and didn’t even know it. 😂
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Honestly. either have I but when you buy an amp used like I 99% of the time do it's a bit of a gamble.
Back up is surely the way to go. Trusty FM9 will be stowed away!

Good posts, thanks fellas!
 
I have never broken a string on an electric except for the high e, and no one is really sure what the hell that string is there for anyway..
 
Never had any tube fail while playing with the band honestly. On the other hand, I've had a few buddies having issues with digital boards tho.
 
cragginshrd said:
Honestly. either have I but when you buy an amp used like I 99% of the time do it's a bit of a gamble.
Back up is surely the way to go. Trusty FM9 will be stowed away!

Good posts, thanks fellas!
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All I used was 2nd hand 70’s and 80’s Marshall’s and for a short while, a used 5150. Never taken to techs, never had anything checked.
 
I have a spare pair of power tubes but always have a backup head. Recently had a guy step on and mash a pair of cables mid song and my Wizard rig went silent :rolleyes: Of course I thought it was the amp, so mid song I swapped out heads for my JEL20 backup. Figured out what was up during a break and went back to the Wizard, but that was the last time I played that JEL20 :ROFLMAO:
 
Honestly, in the short term, you don't need to bias shit. Of course its preferable, but your amp isn't going to catch on fire because the tubes are a little mismatched.

Over the years I can count on two fingers how many times an amp has gone squirrely and its been tubes at gigs.
 
I usually wear a fingerless oven mitt on my picking hand during the gig in case a tube goes down and I need to make a quick change. I screwed one of those plant hanger hooks into the side of my cab to hang it on since it gets a bit warm to wear during summer gigs.
 
VonBonfire said:
I usually wear a fingerless oven mitt on my picking hand during the gig in case a tube goes down and I need to make a quick change. I screwed one of those plant hanger hooks into the side of my cab to hang it on since it gets a bit warm to wear during summer gigs.
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TIL Michael Jackson ran tube amps.
0_Michael-Jackson-sports-a-white-glove-during-his-fi.jpg
 
There are so many small, inexpensive & decent sounding solutions for a backup rig these days; going direct or just having a spare amp on hand.

I’d never try to troubleshoot an amp issue on the spot like that.
 
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