noname Posted February 18, 2004 Report Share Posted February 18, 2004 First off, I realize that this isnt a guitar question. Its an amp question. how do you tell when your preamp tubes need replacing? I know they shouldent need it for 20 years or more, but my amp got knocked over a month ago and hasnt sounded right since. Its a Peavey Classic 30, I have had it for about 2 years, I just replaced the EL84 Sovtek power tubes with a matched quartet of Groove Tubes EL84s this past weekend. Its sounding better, but still goofy. I played a classic 30 at the music store, and it still sounds WAY different, it actually has crunch at the store. The sound right now is really bassy, kinda trebley, but NO midrange. It sounds awful. It has electro harmonics 12AX7EH (3 of them) preamp tubes. So, I dunno, Im getting frusterated, so If you could help me that would be great. Thanks so much! Quote Link to comment Share on other sites More sharing options...
jbkim Posted February 19, 2004 Report Share Posted February 19, 2004 how do you tell when your preamp tubes need replacing? I know they shouldent need it for 20 years or more... 20 years?!?!? I thought 2 years. Hmm... I did let one set go for 14 years though . The EH's shouldn't be more than ten bucks a piece, it might be worth the $30 to see if that'd fix the problem after being knocked over. Quote Link to comment Share on other sites More sharing options...
ansil Posted February 19, 2004 Report Share Posted February 19, 2004 i got quite a few tubes lying around.. i could see if i have some 12ax7 types if you want.. if i have some you culd have them as i am workign with pentodes more now.. Quote Link to comment Share on other sites More sharing options...
Drak Posted February 19, 2004 Report Share Posted February 19, 2004 It could be a lot of things. I would find a qualified tech and just let them look it over and check it out instead of possibly wasting money taking pot-shots in the dark.. Even if it happens to be a pre-amp tube, you'll know it's been given the once-over. But take some time and get a referral from someone locally, don't just take it to 'anyone' out there... BTW, when you installed the new quartet, did you check the bias and adjust it? What area do you live in? Quote Link to comment Share on other sites More sharing options...
noname Posted February 19, 2004 Author Report Share Posted February 19, 2004 The classic 30 is fixed bias, so i dont need to bias it. . . I live in Dallas, Texas USA. No any good amp techs round here? There are no "Mom and Pop" type stores around here that I know of. I bought it at Zoo Music, which is a local, 2 location shop. But they dont have a tech, so they would have to ship it away for a while to I dont know where. . . to nyjbkim: the POWER tubes last last about 2 years. But the PREAMP tubes arent supposed to go out for 10 years or more. Unless they get messed up somehow. ansul: I wasnt really asking for handouts, but if you dont want them, I'll pay shipping. Are they new? I really appreciate the advice. I have tried www.musicianforums.com and the harmony central forums and nobody pays the slightest bit of attention. Quote Link to comment Share on other sites More sharing options...
noname Posted February 19, 2004 Author Report Share Posted February 19, 2004 oh, and what if I were to get some of these? http://www.torresengineering.com/groovtubec.html they are supposed to replace 12AX7's for a hotter, midrange boosted tone. It would be nice to get a bit more bite out of my tame overdrive. Quote Link to comment Share on other sites More sharing options...
Drak Posted February 19, 2004 Report Share Posted February 19, 2004 I threw up some posts in other forums, should have some good recommends for you by tomorrow. I would steer clear of buying this tube or that tube because of some seller's 'hype' unless you really understand -exactly- what it is they're selling you, unless you understand the history of the more popular tube manufacturers of yesteryear compared to the generally accepted quality of today's current production tube manufacturers.. Unless you can see thru what it is they're hyping to you, save your money and spend it on something you know you'll get some bang for the buck out of. Trying and buying different tubes 'can' be tonally profitable, but only when you have a pretty well-rounded knowledge of tube manufacturers and the history behind them. THEN you have some knowledge with which to base your purchase decisions on. Not knowing that will just lend you to be parted with your money with not much tonally to show for it. The best tube deals are on e-Bay and local TV/radio/Ham swap meets anyway, but you have to know what you're looking at. Buying current Yugoslavian-made 12AX7 tubes from Dan Torres, well, I wouldn't. Just me tho. Quote Link to comment Share on other sites More sharing options...
Phil Mailloux Posted February 19, 2004 Report Share Posted February 19, 2004 You should check out the www.ax84.com website and forum, these guys build guitar tube amps for a hobby. They'll definitely know anything you throw at them about tube amps. Quote Link to comment Share on other sites More sharing options...
Hotrock Posted February 19, 2004 Report Share Posted February 19, 2004 You should check out the www.ax84.com website and forum, these guys build guitar tube amps for a hobby. They'll definitely know anything you throw at them about tube amps. Yup. Or ask at www.18watt.com They're a nice bunch and know what they're on about. Quote Link to comment Share on other sites More sharing options...
Drak Posted February 19, 2004 Report Share Posted February 19, 2004 ...and the -very- first thing any responsible member of either of those sites would tell you is if you don't normally work on amps or have a well-founded understanding of electricity, or have no decent test equipment of your own to work with, then don't even bother to remove the chassis, as the voltages inside the average amp are lethal enough to kill you, or seriously injure the unwary 'tinkerer'. So unless someone tells me they're used to being inside their own amp (which noname has not mentioned yet), I won't be the one to recommend they try and fix it themselves. Mentioned to the wrong person, that can be wreckless internet advice. But if noname 'is' used to working on his own amp, then yes, those are good sites to start. Along with: Ampage TheAmpWorkshop The FDP Amp Section The TDPRI Amp section ...and many other tube amp sites. Quote Link to comment Share on other sites More sharing options...
Hotrock Posted February 19, 2004 Report Share Posted February 19, 2004 ...and the -very- first thing any responsible member of either of those sites would tell you is if you don't normally work on amps or have a well-founded understanding of electricity, or have no decent test equipment of your own to work with, then don't even bother to remove the chassis, as the voltages inside the average amp are lethal enough to kill you, or seriously injure the unwary 'tinkerer'. So unless someone tells me they're used to being inside their own amp (which noname has not mentioned yet), I won't be the one to recommend they try and fix it themselves. Mentioned to the wrong person, that can be wreckless internet advice. Amen to that brother! Quote Link to comment Share on other sites More sharing options...
KeithHowell Posted February 19, 2004 Report Share Posted February 19, 2004 Have a look on Geofex as well R.G.Keen knows plenty about tubes amps. Keith Quote Link to comment Share on other sites More sharing options...
jbkim Posted February 19, 2004 Report Share Posted February 19, 2004 to nyjbkim: the POWER tubes last last about 2 years. But the PREAMP tubes arent supposed to go out for 10 years or more. Unless they get messed up somehow. Hmm... really? I've seen recommendations such as here and here with the "power amp tubes should be replaced twice as often as preamp tubes" (1 year power / 2 year pre) rule of thumb... but then those are vendor sites that probably wants to sell more tubes but after doing a little searching, I found some suggesting that preamp tubes can last up to 30 years with a "if they still sound good to you" caveat. I guess let your ear and wallet be your guide . Quote Link to comment Share on other sites More sharing options...
Hotrock Posted February 19, 2004 Report Share Posted February 19, 2004 I always thought that tubes were reliable for long periods of time, providing that they're left on. I think the major wear (if that's the word) occurs when turning them on and off. After it's fixed, maybe you should leave it on for the next 40 years Quote Link to comment Share on other sites More sharing options...
Drak Posted February 19, 2004 Report Share Posted February 19, 2004 Power tubes just depends on how often you use your amp. More playing time = more wear on power tubes. If you regulary gig your amp 1-5 times a week, then I believe expected life-span is up to 3-5 years, depending on the type of amp and tube. Just downsize from there the less the amp is used. If your amp has a standbye switch and you use it properly, you'll extend the life of your tubes (referring to the quote about turning the amp on and off a lot wears them out) Newer production tubes (JJ's, Svets, Ruby, etc.,) have a shorter expected life-span than old NOS power tubes will. That's one reason why old 40 year old NOS tubes are worth so much, sometimes up to $400.00/pr (ridiculous) as compared to some new Svets that you can buy for $40.00/pr. Pre-amp tubes last -much- much longer unless your pre-amp section runs them hard, (i.e. most Mesa type amps that have cascading gain type pre-amp sections ), I buy 'em used and they're sometimes 40 years old and still rockin' the house and very toneful with lots of life left on them. I never buy used (UOS) power tubes, but I have no problem buying used pre-amp tubes at all, those are some of the best deals around. You can find them cheap by the lot on e-Bay and it's fun to swap 'em in and out and experiment with them. PS, for anyone who doesn't already know, GrooveTubes just takes current production Russian, Chinese, and Yugoslavian tubes, matches them up, rebrands them with the GT logo, and re-sells them. So GT tubes are what are termed 'Rebranded' tubes, FWIW. Quote Link to comment Share on other sites More sharing options...
noname Posted February 19, 2004 Author Report Share Posted February 19, 2004 I thank all for the help. Quote Link to comment Share on other sites More sharing options...
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