#1
So I might be buying a used SVT-4 Pro from GC tomorrow. I'll most likely make them open it up so I can take a peak inside and see how things look. The amp itself looks like it sat in someone's studio and never moved. Based on the serial number it's about 5 years old.

When they pop it open, how can I tell what kind of condition the tubes are in? If they need replaced or will need replaced soon I'd like to talk them down in the price. The SVT-4 Pro has a solid state power amp and tube pre amp. If the amp sounded great in the store, no tone issues from what I can tell, is it safe to assume the tubes are in pretty good condition?
#2
Tubes aren't something that you look at and determine their condition. Playing the amp would be the only way to tell, short of testing the tubes in a dedicated tester - and even then, they're not tested under actual operating conditions, like in an amp.

Worn tubes may exhibit the following:

Volume dropout
Changing volume
Muddy tone
Popping noises

Edit: With a solid state amp, that certainly lowers the cost to repair. Chances are, it uses 12AX7 tubes in the preamp. You can buy them for about $12 each. The nice thing about preamp tubes, is they last almost forever. Chances are, they're still in excellent condition and would probably test as "new."
Last edited by KG6_Steven at Aug 6, 2010,
#3
Don't worry about it, a preamp tube won't die for a very long time. My tube amp which is coming on 30 years old only had it's preamp tubes replaced for the first time this year, and that was only because I wanted to try some new tubes and tweak the sound.
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#4
Slight thread jack but would overdriving a tube amp or poweramp cause the tubes to deteriorate faster?
Also would it be worth getting a solid state amp with a tube preamp rather than a tube amp alone?
#6
Quote by Spaz91
Slight thread jack but would overdriving a tube amp or poweramp cause the tubes to deteriorate faster?
Also would it be worth getting a solid state amp with a tube preamp rather than a tube amp alone?



Overdriving a tube preamp? Probably minimal. Those tubes are low output and should last quite awhile.

Overdriving a tube power amp? Yes. Making those tubes work harder makes them hotter and does wear them out faster.

Is it worth it getting a tube preamp with a SS power amp? Well, that all depends on what you're looking for. A lot of guys, myself included, feel like you lose all the tube warmth as soon as you feed the signal into a transistor output section. There are quite a few who snicker at the tube preamp/transistor output amps. The bottom line is that tubes, even power tubes, will last 2 to 4 years, give or take. That gives you plenty of time to save up for new ones. Buying a matched pair of most power tubes isn't all that expensive. Buying preamp tubes is cheap and they last for years.

That's my take on it.