JonathanD Posted June 9, 2006 Share Posted June 9, 2006 How do you know when to chang preamp tubes? I have an SVT4 and it has 3 12AX7 preamp tubes in it, I have had it for about 1 year and a half, and it was in the store for about a year. Can i cause damage by not changing them before they fail in a preamp section? they still sound good, and i just got back ups, but i ahve never had experiance with knowing when to change tubes save when someone brought it to the shop and a power tube was busted, burnt or had a hole in it. thanks for the help. Jonathan BTW, I have an audition for band in Chicago, I'm hopeful. Have a great time guys, Jonathan Link to comment Share on other sites More sharing options...
Rocky McDougall Posted June 9, 2006 Share Posted June 9, 2006 Johnathan, I have a couple of amps/preamps that have the original tubes. I bought them in 1955. That is over 50 years and they still sound the same to me. Maybe there may be a slight sonic difference with new tubes, I really don't know, I'm sure there are some on this forum who do know, and they can advise you. My position is, don't change them unless they stop working. Rocky "Democracy is two wolves and a lamb, voting on what to eat for lunch. Liberty is a well-armed lamb, contesting the vote." Benjamin Franklin Link to comment Share on other sites More sharing options...
JonathanD Posted June 9, 2006 Author Share Posted June 9, 2006 Thats what i was leaning towards. I always treat them good, warm them up, let them cool down before i go outside in the cold. Thanks for reinforcment. Jonathan Link to comment Share on other sites More sharing options...
JonathanD Posted June 9, 2006 Author Share Posted June 9, 2006 Sorry, double post: Holy shnikies! You bought an amp in 55. It still works, and the tubes still do good. Amazing. Either we have become more capitalist and made equiptment to break down faster or you really know how to treat an amp. Link to comment Share on other sites More sharing options...
Rocky McDougall Posted June 9, 2006 Share Posted June 9, 2006 Actually they have had rather rough treatment over the years, not on purpose mind you, just hauling them around in the trunk of my car going to different gigs. Could not afford a van or truck much less a roadie. Just don't bang on them with a hammer and they should last a good while. Rocky "Democracy is two wolves and a lamb, voting on what to eat for lunch. Liberty is a well-armed lamb, contesting the vote." Benjamin Franklin Link to comment Share on other sites More sharing options...
picker Posted June 9, 2006 Share Posted June 9, 2006 It also depends on the amp. A high gain hot rodded amp will burn through power tubes at varying accelerated rates, but the preamp tubes should last a good long time in a vintage amp from the 50's. On a Bass amp, which is not normally pushing tubes into distortion, your praamp tubes ought to go for quite a few years without needing replacement, barring mishap. Always remember that you are unique. Just like everyone else. Link to comment Share on other sites More sharing options...
alexclaber Posted June 9, 2006 Share Posted June 9, 2006 Preamp tubes need changing about as often as preamp transistors. And when did you last change those? Alex Barefaced Ltd - ultra lightweight, high ouput, toneful bass cabs Link to comment Share on other sites More sharing options...
Yogi Posted June 9, 2006 Share Posted June 9, 2006 I had to change out my power tubes on one of my amps recently because they were making a really unpleasant buzz. I changed out the preamp tubes at the same time. Depending on how much you use the amp, and how hard you push it, I would think you'd be due for a re-tube once every 12-18 months or so. Then again, if it only gets switched on 12 times a year, they'll last longer. YMMV. "Expectations are the enemy of music." - Mike Keneally Hi! My band is... my band is... HALF ZAFTIG | Half Zaftig on MySpace | The Solo Stuff Link to comment Share on other sites More sharing options...
Big Red 67 Posted June 9, 2006 Share Posted June 9, 2006 Doesn't Fee change like every other tune? Oh, wrong Tubes! Sorry! Big Red's Ride Blog Link to comment Share on other sites More sharing options...
Fred TBP Posted June 9, 2006 Share Posted June 9, 2006 It's like changing the oil in your car: if you do it on a regular cycle (every 3,000 miles) your car will run mostly problem-free for years. If you constantly put it off until it turns black and gunky, that engine is going to need serious maintenance in a few years. Preamp tubes will last for years, like everyone says. Sometimes if an amp runs hot under normal use or if you have a tendency to run everything on 11 you should check them every other year, but I don't. Power tubes will last about 1-2 years depending on how often you use the amp and how much ventilation runs through it. I usually install a little fan on some of my hotter amps, like in the back of an SVT head. Good ventilaton will help that tube last closer to 2 years in my experience. What you didn't ask, and you should know, is that the output (paper) filter capacitors (the big ones next to the power transformer) are electrolytics and tend to dry out after 2-3 years, so it's best to get the whole head tested every 2 years. Yeah, it costs to maintain tube amps, (I spend about $200 every other year on my SVT head) but this is how you keep good equipment running for 20-30 years in my book. Link to comment Share on other sites More sharing options...
JonathanD Posted June 10, 2006 Author Share Posted June 10, 2006 Originally posted by Fred the bass player: What you didn't ask, and you should know, is that the output (paper) filter capacitors (the big ones next to the power transformer) are electrolytics and tend to dry out after 2-3 years, so it's best to get the whole head tested every 2 years. Yeah, it costs to maintain tube amps, (I spend about $200 every other year on my SVT head) but this is how you keep good equipment running for 20-30 years in my book. Does this go for amps that only had tubes for the pre amp and solid stae for the power amp? also, cars DO NOT need their oil changed every 3000 miles. Even in my owners manual it says that(I have an 94 Audi). From what i understand you can go 5,000-10,000 with no problem just so long you change the filter every time. Link to comment Share on other sites More sharing options...
jeremy c Posted June 10, 2006 Share Posted June 10, 2006 If the tubes are glowing blue instead of orange, I might check them. Or is it orange instead of blue? Free download of my cd!. Link to comment Share on other sites More sharing options...
JonathanD Posted June 11, 2006 Author Share Posted June 11, 2006 Orange is good. Or at least I would hope since new tube anps tubes glow orange Link to comment Share on other sites More sharing options...
Big Daddy from Motown Posted June 11, 2006 Share Posted June 11, 2006 It is totally untrue that filter caps leak after a year or two. Typical life of an electrolytic filter cap would be 10 to 15 years. Preamp tubes should be replaced when the amp tone sounds weak or noisey the best way to check them is to replace them one at a time with a known good tube. If the amp sounds better with the new tube it's time to replace the preamp tube. Link to comment Share on other sites More sharing options...
Tom Capasso Posted June 12, 2006 Share Posted June 12, 2006 I couldn't help myself - a preamp maker (and once-upon-a-time luthier) provided a funny bit about this. Worth A Click Tom www.stoneflyrocks.com Acoustic Color Be practical as well as generous in your ideals. Keep your eyes on the stars and keep your feet on the ground. - Theodore Roosevelt Link to comment Share on other sites More sharing options...
Fred TBP Posted June 12, 2006 Share Posted June 12, 2006 Originally posted by dnkritr: Originally posted by Fred the bass player: What you didn't ask, and you should know, is that the output (paper) filter capacitors (the big ones next to the power transformer) are electrolytics and tend to dry out after 2-3 years, so it's best to get the whole head tested every 2 years. Yeah, it costs to maintain tube amps, (I spend about $200 every other year on my SVT head) but this is how you keep good equipment running for 20-30 years in my book. Does this go for amps that only had tubes for the pre amp and solid state for the power amp? No, I think with those you could slide an extra year or two out of those output caps as the power transformers are significantly smaller and do less work in those kind of amps. Originally posted by dnkritr: also, cars DO NOT need their oil changed every 3000 miles. Even in my owners manual it says that(I have an 94 Audi). From what i understand you can go 5,000-10,000 with no problem just so long you change the filter every time. Agreed, which is why I didn't use the word "need". (there are other factors involved.) Link to comment Share on other sites More sharing options...
tumbao Posted June 15, 2006 Share Posted June 15, 2006 I use a '68 Ampeg B-12N Fliptop. I've had it for about 15 years. I replaced the power tubes when I bought it because they crackled after being on for an hour. 3 years ago I retubed the whole amp as the preamp tubes had become microphonic - excessively amplifying physical vibrations, e.g. tapping the top of the amp with your finger can be heard through the speaker. I understand that this happens to tubes over time (not sure if use alone affects it). While having it retubed, it was discovered that one of the original filter caps was bad - I had noticed diminshed output for a year or so. The others are fine. I also had problems with newer preamp tubes (6SL7) buzzing. I eventually returned them for NOS (New Old Stock) versions and that corrected the problem. If I stayed on top of it, I would have no problem rationalizing replacing tubes every 5 years or so, having experienced a few problems now. I also have a '98 Eden WT400 with a 12AX7 preamp tube that I've never replaced. I've used this amp much less than the Ampeg, but I've never noticed any problems with the tube. Some things I have come to understand from various sources about old tube amps: - The output transformers benefit from use. Mine is still good. I have used quite a bit (for about 6 years it got a solid 500-600 hours/year) - If there's a manual bias adjustment, it pays to have it adjusted by a professional. It affects the performance of many of the tubes (ones with grids). An improper adjustment can affect the quality of the amp, and I believe shorten the life of the tubes. - The heaters in some newer preamp tubes can cause buzzing. Using NOS seems to be a safer bet. Andrew My ampeg: http://andrewnelson.com/B-12N/ Link to comment Share on other sites More sharing options...
JonathanD Posted June 15, 2006 Author Share Posted June 15, 2006 Your right Fred you didnt say "need", My bad . thanks guys. I didn't know if they would have a long and slow decline in sound until one day I'm losing my mind trying to figure out whats wrong with my bass:) and since I have not heard anything about that I am assuming they will not. Jonathan Link to comment Share on other sites More sharing options...
Tenstrum Posted June 15, 2006 Share Posted June 15, 2006 I've been replacing the pre-amp tubes on my 1200s about 1-1/2 to 2 years. One time the tubes sound "microphoney" and another time they sounded a little dirty and distorted(not the good way). I have 2 pre-amp tubes, one for each channel on my amp. Even though I don't use Channel 2 that much, I still replace both tubes at the same time. Tenstrum "Paranoid? Probably. But just because you're paranoid doesn't mean there isn't an invisible demon about to eat your face." Harry Dresden, Storm Front Link to comment Share on other sites More sharing options...
chubby Posted June 16, 2006 Share Posted June 16, 2006 WELL I used my bassman everyday and I had to replace my tubes last year That was the first time in twenty five years. ricky payne Link to comment Share on other sites More sharing options...
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