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Help With Tubes


theitalianrob
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I just got an Ampeg V-50H from the guitarist in my band but im not sure where i can find what kind of tubes it takes.

Also i was wondering what types of tubes are the best. And i was shoping around for preamp tubes and i keep seeing options such as Matched Triodes and Balanced Triodes, what does that mean?

Here http://www.ampeg.com/manuals/V-50H.PDF

Info from that manual...

13. Preamp Tube: 12AX7A / 7025 (1)

14. Power Amp Phase Splitter Tube:12AX7A / 7025 (1)

15,16. Power Tubes: EL34 / 6CA7 (2)

A fairly standard lineup, usually associated with 30 to 60 watt amps (depending on how hard they push the tubes, and how honest they are in the ratings) You can, in fact, push a pair of EL34/6CA7 types as far as 80 to 100 watts - but you need good rugged tubes if they are to survive that. :D

Matching most commonly is preferred/required for the output tubes of push-pull amps - in your case the EL34/6CA7 tubes. These aren't triodes, by the way. This ensures they share the load. However, sometimes, particularly in stereo amps that use one half of a twin triode tube like the 12AX7 in each channel of a preamp, it may be of some benefit to match the 2 halves. It also may be of some benefit for the phase splitter tube. However, I would never bother matching the preamp or phase splitters in a guitar amp. Just buy matched output tubes.

As for brand names. That's a long discussion/argument, and there are many choices. I have been using new Electro-Harmonix tubes with good results. Other names that should/could be good for new tubes are JJ Electronics, Svetlana, Sovtek etc, and then there are manymany NOS (new old stock) tubes, some that sell for huge dollars because people say thay are better than new ones, and we probably shouldn't open those cans or worms here :D

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You don't need a 12A_7 with matched triodes in a guitar amp.

Also, it isn't strictly necessary in the power amp either. Different individual tubes bias differently, which is the reason for using matched power tubes. But as long as you don't have one tube redplating while the other is idling fine, you can use mismatched tubes. You may get less output or less bass, but for a ~50w guitar amp this may not matter to you.

Me, I run one Sovtek and one Chinese 6L6 in my Bassman at the moment. Both glow blue and the amp is loud and normal-sounding, which to me means that in my situation, the mismatched tubes are fine. Now, I use this for bass, so I should probably put some matched tubes in there... but it suits my bass sound well. (My bass sound is aggressive and overdriven.)

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As for brand names. That's a long discussion/argument, and there are many choices. I have been using new Electro-Harmonix tubes with good results. Other names that should/could be good for new tubes are JJ Electronics, Svetlana, Sovtek etc, and then there are manymany NOS (new old stock) tubes, some that sell for huge dollars because people say thay are better than new ones, and we probably shouldn't open those cans or worms here :D

You betcha you'll get a kicking for starting that NOS tube discussion on a sensible forum.

Damnit Jim - we're guitarists, not voodoo practitioners! :D

In all seriousness however, you really need to know the ground for NOS tubes and some are worth the cash. That said, arguing that all NOS beats modern production stock hands down is a fallacy in most cases. But not all, of course. It's like comparing a vintage Fender to a modern Fender....the modern production is better in terms of accuracy and consistency but you do get some vintage stinkers amidst the old gems.

I'll shut up now before I have to warn myself.

Edited by Prostheta
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You don't need a 12A_7 with matched triodes in a guitar amp.

Yes, as I said, that's usually a hifi consoderation. However, the 12A*7 tubes used in the phase splitter can unbalance the drive to the output tubes, resulting in less power out before distortion occurs - which may or may not be a good thing :D )

Also, it isn't strictly necessary in the power amp either. Different individual tubes bias differently, which is the reason for using matched power tubes. But as long as you don't have one tube redplating while the other is idling fine, you can use mismatched tubes. You may get less output or less bass, but for a ~50w guitar amp this may not matter to you.

Some tubes are matched for gain as well as just where they bias. Full matching will enure you maximise what you can get from the amp, but as you say - it often just isn't necessary. Still, a lot of places don't charge very much extra for matched tubes, so you might as well, I figure.

Me, I run one Sovtek and one Chinese 6L6 in my Bassman at the moment. Both glow blue and the amp is loud and normal-sounding, which to me means that in my situation, the mismatched tubes are fine. Now, I use this for bass, so I should probably put some matched tubes in there... but it suits my bass sound well. (My bass sound is aggressive and overdriven.)

Blue glow, at the glass is just phospherescence of the glass and not a problem. Blue glow inside the tube space indicates some gassification. A little bit doesn't matter, but a lot can mean you should get a new tube before it fails.

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As for brand names. That's a long discussion/argument, and there are many choices. I have been using new Electro-Harmonix tubes with good results. Other names that should/could be good for new tubes are JJ Electronics, Svetlana, Sovtek etc, and then there are manymany NOS (new old stock) tubes, some that sell for huge dollars because people say thay are better than new ones, and we probably shouldn't open those cans or worms here :D

You betcha you'll get a kicking for starting that NOS tube discussion on a sensible forum.

Damnit Jim - we're guitarists, not voodoo practitioners! :D

In all seriousness however, you really need to know the ground for NOS tubes and some are worth the cash. That said, arguing that all NOS beats modern production stock hands down is a fallacy in most cases. But not all, of course. It's like comparing a vintage Fender to a modern Fender....the modern production is better in terms of accuracy and consistency but you do get some vintage stinkers amidst the old gems.

I'll shut up now before I have to warn myself.

i agree

i have a old tube works amp with one 12ax7 i have tried several diffent tubes some new some i don't have a clue and the one i like the best just says 12ax7 and then in little red letters CHINA

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i also have a quick question, is there a difference between short plate and long plate preamp tubes?

Yep, when you look inside, you'll see the plates have different lengths :D There's also black plate, and smooth plate etc etc.

Seriously though, the electrical specs are the same. Knowing whether it is a long or a short plate version helps identify who made it and when. This info helps people choose the particular tube that they think will give the best sound - particularly used and NOS expensive rare ones - but as we said, we shouldn't get into that discussion :D

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i agree

i have a old tube works amp with one 12ax7 i have tried several diffent tubes some new some i don't have a clue and the one i like the best just says 12ax7 and then in little red letters CHINA

What you are doing is known as tube "rolling". The one that is best depends on a lot of things, not least, your own preferences. Also, it depends on how the tube's foibles interact with the rest of the amp and speaker et al. Cheap Chinese tubes have at times had a bad reputation for reliability, but not always, and I believe they are getting better all the time. If you like that particular tube, be happy !

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