Dub-T-123 Posted January 1, 2012 Posted January 1, 2012 My ac30 started making some weird noises. Sometimes when I play there will be this weird sound buried under my guitar sound. It's not really static or noise, it's this weird glitchy sound that changes pitch and stuff. Kind of like the sound a Fuzz Factory makes when you're starving it and a note decays and changes pitch randomly. I thought maybe the switch on my Fuzz Factory broke and it's bleeding some effected signal through but my amp still does it when I'm plugged straight in. Some times it gets really bad and just makes that sound when I'm not playing. It's like some kind of weird feedback. If I put it on standby and then turn it back on it might go away for a while but then it comes back. I'm not gonna lie, I just built a Zvex Super Duper 2 in 1 booster pedal and I've been absolutely slamming my amp with it all weekend. I really only used the regular Super Hard On side turned all the way up though. I'm not sure if that's really enough boost to damage it. Do you guys think it's a microphonic tube or something? I'm not really sure what a microphonic tube would sound like. I'm pretty handy and poor so taking it to an amp tech is a little out of the question.
surfpup Posted January 1, 2012 Posted January 1, 2012 Tube is likely - preamp most likely. Not necessarily a micro phonic tube (which generally leads to a ringing, following feedback) but a bad preamp tube sounds likely to me. I'd swap in a good/new preamp tube one at a time until I found the culprit. Next possibility would be the power tubes. Then again it could be the flux capacitor too!
Dub-T-123 Posted January 1, 2012 Author Posted January 1, 2012 Lol fingers crossed hoping its not a flux capacitor. This should be pretty wild trying to find the culprit. This amp is physically impossible to open. No lie, you can't just get to the tubes in any reasonable way. Are all the preamp tubes the same? Could I just buy one tube and swap it in until I find the culprit? The sound isn't very loud btw if that's any help
stein Posted January 1, 2012 Posted January 1, 2012 Usually, with a tube amp it will be a tube that causes the problem. Those tubes in the AC-30 are hard to get to, aren't they? Whenever I encounter such a thing, I will give some of the tubes a little thump and maybe rock them a little to check the connections. Often, the problem tube will make noises and such to tell you it is that tube. Also, connections get corrosion sometimes. If that doesn't do, like suggested, replace one at a time.
Dub-T-123 Posted January 1, 2012 Author Posted January 1, 2012 Those tubes in the AC-30 are hard to get to, aren't they? Yes. It's the ultimate PITA. Not a very good design at all in that regard.. Thanks for the tip. The amp is at my drummers house right now but I'll give that a try when I get it back.
surfpup Posted January 1, 2012 Posted January 1, 2012 Unfortunately the AC30 has a lot of tubes... 4 EL84, 3 ECC83/12AX7, and one GZ34 rectifier tube. It sounds like you are rolling without spares (living dangerously are we?). If it's power tubes, you really need to replace all 4 with a matched quad (which you should be carrying as spares anyway ) It it's a preamp tube, you can just buy one 12AX7 and swap it into each of the three until you find the culprit. Another (though costly) option is to replace all the tubes and keep the ones you have as spares. A set for the AC30 will cost you about $95. How old are the tubes? (AC30s are known to be hard on power tubes (EL84) so they may need replacing anyway.
Jeff-7 Posted January 1, 2012 Posted January 1, 2012 Ac30s are the biggest pita in that regard, have to take the entire chassis out to get to the tubes. I'm actually tossing around the idea of buying new tubes vs. a van amps solemate reverb at the moment. Getting a weird metallic sounding rattle when I play certain notes and it's beginning to bug me a bit, which is a good excuse to toss those crappy chinese rebrands they come stock with.
Dub-T-123 Posted January 1, 2012 Author Posted January 1, 2012 Yeah I don't have any spares or anything. I've only replaced the rectifier so the others are just the ones it came with. I bought the amp used, I'm not sure how old it was at the time, but I've probably had the amp for around 2 years or so. Any recommendations for tubes? I play kinda psychedelic rawk most of the time. I like my amp pretty loud (but not dimed) on the edge of clean type of sound. Think like the album Dual Mono by the Greenhornes.
stein Posted January 1, 2012 Posted January 1, 2012 Unfortunately the AC30 has a lot of tubes... 4 EL84, 3 ECC83/12AX7, and one GZ34 rectifier tube. It sounds like you are rolling without spares (living dangerously are we?). If it's power tubes, you really need to replace all 4 with a matched quad (which you should be carrying as spares anyway ) It it's a preamp tube, you can just buy one 12AX7 and swap it into each of the three until you find the culprit. Another (though costly) option is to replace all the tubes and keep the ones you have as spares. A set for the AC30 will cost you about $95. How old are the tubes? (AC30s are known to be hard on power tubes (EL84) so they may need replacing anyway. Yes, all amps I know of or have any experience with seem to eat up EL-84 tubes. You can still replace the power tubes one at a time to diagnose or find a bad one, but if you do replacing all 4 is not only the best for the amp (and tone), but it also tells you the rest might be ready to go as well.
Jeff-7 Posted January 1, 2012 Posted January 1, 2012 General consensus lately on tubes for the 12ax7s are 2x Tung sol reissues and an Electro Harmonix in the phase inverter position. JJ EL84s and the GZ34 have been getting great reviews.
surfpup Posted January 1, 2012 Posted January 1, 2012 General consensus lately on tubes for the 12ax7s are 2x Tung sol reissues and an Electro Harmonix in the phase inverter position. JJ EL84s and the GZ34 have been getting great reviews. I'd agree on the Tung Sol, though I might lean toward Mullard reissues for the EL84s.
Dub-T-123 Posted January 1, 2012 Author Posted January 1, 2012 Ac30s are the biggest pita in that regard, have to take the entire chassis out to get to the tubes. I'm actually tossing around the idea of buying new tubes vs. a van amps solemate reverb at the moment. Getting a weird metallic sounding rattle when I play certain notes and it's beginning to bug me a bit, which is a good excuse to toss those crappy chinese rebrands they come stock with. Yeah seriously who's idea was it to make them like that? Mine rattles a bit too. It's hardly noticeable in regular playing situations for me though. Btw for tube recommendations I don't have the cash for super expensive tubes. Just whatever sounds good and lasts a while for a reasonable price I guess.
Jeff-7 Posted January 1, 2012 Posted January 1, 2012 For the entire set like I described just ordering through amazon it puts you back $104.00. I had actually just looked them all up an hour ago haha. This includes a matched quad of EL84s. You could go through all the dealer sites to find the best price but Amazon sells them from the tube distributors you'll search for anyways at generally the same price.
Dub-T-123 Posted January 1, 2012 Author Posted January 1, 2012 Thanks man. That sounds cool to me. I think I'm gonna go the cheapo way first and just get one EL84 to swap in different positions to see if that fixes it, and if that doesn't work, I'll just replace the whole set. Thanks for all the help guys
stein Posted January 1, 2012 Posted January 1, 2012 Yeah I don't have any spares or anything. I've only replaced the rectifier so the others are just the ones it came with. I bought the amp used, I'm not sure how old it was at the time, but I've probably had the amp for around 2 years or so. Any recommendations for tubes? I play kinda psychedelic rawk most of the time. I like my amp pretty loud (but not dimed) on the edge of clean type of sound. Think like the album Dual Mono by the Greenhornes. I haven't tried anything in an AC-30, but for tubes I like in the EL-84, I think the JJ or the Electro-Harminix are the best sounding, and very different from each other. The sovtek or the Chinese ones I havn't found anything they sound good in. And, I haven't tried the newer Mullard EL-84. I wouldn't personally use or gig with NOS EL-84, because they wouldn't last long. For 12ax7, I would try and get access to a used bin that a lot of shops or repair places have, because they are usually cheap, and most repair places replace tubes before they are due. You can find a lot of tubes to try that way, and get some older american or british tubes that sound good and have lots of life left. The idea is to experiment, to try and find tubes that SOUND better in a particular amp. The best way to get a tube amp to sound great is with tubes types/brands that the amp likes the best.
alexri Posted January 1, 2012 Posted January 1, 2012 Does it sound "computery?". I thought there was something wrong with my Roland JC120 cause it was making those noises, then I found out it's actually the cords I'm using; the $6 rapco ones.
Dub-T-123 Posted January 1, 2012 Author Posted January 1, 2012 Does it sound "computery?". I thought there was something wrong with my Roland JC120 cause it was making those noises, then I found out it's actually the cords I'm using; the $6 rapco ones. Yes. At first I thought it was a problem with my El Capistan (a digital delay pedal) because I was running it off of the same power supply as my other pedals, and I thought maybe it was having some weird glitches due to being underpowered, but then I tried plugging straight in and it still made the sound. My cables are starting to crap out on me. I'll try it with some different cables, but I seem to remember the amp making this sound with nothing plugged in at all. I dont remember I'll have to check it out.
surfpup Posted January 1, 2012 Posted January 1, 2012 Definitely need to try it plugged straight in - and with different cables to make sure it's not in a pedal or cable somewhere.
Dub-T-123 Posted January 2, 2012 Author Posted January 2, 2012 Well, if the tubes weren't ****ed before, they probably are now. I accidentally left the amp on standby for almost 24 hours straight. I can be such a ****** sometimes..
stein Posted January 2, 2012 Posted January 2, 2012 Well, if the tubes weren't ****ed before, they probably are now. I accidentally left the amp on standby for almost 24 hours straight. I can be such a ****** sometimes.. AW, take it easy...sometimes I do that just to break them in. Leaving an amp on a day unattended ain't the most 'responsible' thing, mainly because if something were to go wrong, you would'nt be there to turn it off. But, leaving an amp on standby for a day should not CAUSE any damage to the amp OR the tubes.
Guest farnsbarns Posted January 2, 2012 Posted January 2, 2012 Well, if the tubes weren't ****ed before, they probably are now. I accidentally left the amp on standby for almost 24 hours straight. I can be such a ****** sometimes.. This should do no harm at all. I have been known to leave mine for days sometimes.
djroge1 Posted January 3, 2012 Posted January 3, 2012 You should buy at least 1 12AX7 for a back up (the more the better but I get the no $$). 1. Plug the guitar straight into the amp and see if the sound is still there. 2. Swap guitar cords and see if the problem exists. 3.I would swap a 12AX7 around first and see if it helps. Swap one and try it out. If the sound is still there, turn the amp off and let it cool and take that new one out and put it in the next spot. Swap them around one at a time. 4. If it's not the pre-amp tube (My bet is that it is pre-amp) then try the power tubes. Lastly try the the EDIT: rectifier tube (it used to say phase inverter tube). Normally, I would begin at V1 (the tube closest to the input) but since you said it is real quiet you might want to start at the other end. The reason for this is because if it was in V1 the sound would get louder as it went thru each pre-amp tube. All sounds increase as it passes thru each gain stage. No worries about leaving you amp in standby for that length of time. For break in after I build an amp I leave the amp on standby for a full day - I play it for a while, leave it on standby, play some more etc...
djroge1 Posted January 3, 2012 Posted January 3, 2012 Yes. At first I thought it was a problem with my El Capistan (a digital delay pedal) because I was running it off of the same power supply as my other pedals, and I thought maybe it was having some weird glitches due to being underpowered, but then I tried plugging straight in and it still made the sound. My cables are starting to crap out on me. I'll try it with some different cables, but I seem to remember the amp making this sound with nothing plugged in at all. I dont remember I'll have to check it out. This could be an indicator of the phase inverter which I believe is the V3
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