:oilpit: Posted May 6, 2009 Share Posted May 6, 2009 Just got a JTM off ebay, it came with the tubes out. I put them in and ran it on standby for a few hours, then plugged it into my cab and have been playing it (I'd say it's gotten about 5 hours) When a guitar is plugged into it, and not being played it makes a weird crackling noise, it is loudest and most prominent right as I turn standby off. It's not too loud and goes away when it's being played (or it is just drowned out by the speakers, I'm not sure) It's not that big of a deal, I just want to make sure that the amp is working properly, and I'm not hurting it by playing it. The only thing that I would think could possibly cause this is that I have ran it at 8 and 16 ohms (going into a 16 ohm cab) reason is, I've been told from reliable sources that I should run it at 8 and from other reliable sources that I should run it at 16 (I'm still not sure which is right) Sorry for the long post, I really appreciate any possible info... Link to comment Share on other sites More sharing options...
myspace.com/jessenoah Posted May 6, 2009 Share Posted May 6, 2009 sometimes when i "crank" one of the eq knobs, i get weird noises, but mine doesent have any problems Link to comment Share on other sites More sharing options...
retrosurfer1959 Posted May 6, 2009 Share Posted May 6, 2009 Your young with healthy ears keep cranking it up and pretty soon you won't hear any of those noises. Or much else for that matter, retirement accounts, hearing protection and dental floss are all much more important than you think they are when your young. Link to comment Share on other sites More sharing options...
:oilpit: Posted May 6, 2009 Author Share Posted May 6, 2009 Or much else for that matter' date=' retirement accounts, hearing protection and dental floss are all much more important than you think they are when your young. [/quote'] I bought a 10 pack of ear plugs, not 2 hours ago Link to comment Share on other sites More sharing options...
G u e s t Posted May 7, 2009 Share Posted May 7, 2009 Never run the head without a cabinet connected. Always run into a load that matches the head's setting ohms-wise. If you must mis-match - up or down 2x max is acceptable for a while only. Free choice of mismatch, go lower rather than higher..... a 4ohm cab on an 8ohm head will be less damaging to the output transformer than a 16ohm cab on an 8 ohm head. Ideally, don't mis-match at all. Gentle and continuous rustling sounds, like autumn leaves in the breeze means either it is fall, or a tube (maybe a cap or resistor too) is going west. Since tubes are socketed - swap a few from a working amp and see if it goes away - should give you a better idea where the problem is. Turn it up, play loud and enjoy. Link to comment Share on other sites More sharing options...
bluzhammer Posted May 7, 2009 Share Posted May 7, 2009 Oilpit, personally I would take it to a local amp or electronics guy for a quick diagnosis. When I started building "retro" amplifiers, I chased my own tail trying to troubleshoot small problems and glitches. I have found that with about 5 minutes most issues can be solved. Link to comment Share on other sites More sharing options...
80LPC Posted May 7, 2009 Share Posted May 7, 2009 A valve amp has to be matched to the impedance of the cab. A mismatch in either direction causes power to be reflected back to the amplifier. Link to comment Share on other sites More sharing options...
Thundergod Posted May 7, 2009 Share Posted May 7, 2009 A valve amp has to be matched to the impedance of the cab. Indeed, 8ohm, 16ohm? it doesn't matter as long as the cab matches the head (cab 8 then head at 8, cab 16 then head at 16) Link to comment Share on other sites More sharing options...
djroge1 Posted May 7, 2009 Share Posted May 7, 2009 Oilpit' date=' personally I would take it to a local amp or electronics guy for a quick diagnosis. When I started building "retro" amplifiers, I chased my own tail trying to troubleshoot small problems and glitches. I have found that with about 5 minutes most issues can be solved. [/quote'] +1 for this perhaps after you try the tube swap mentioned by guitarest above. I know when I built my amp I had some crackling sounds at first and it turned out to be a cold solder joint. However, I don't have a standby switch. An experienced amp tech will locate the problem if the seller doesn't have any ideas. You said it was a clone so if the seller built the amp then they may have a good idea. Link to comment Share on other sites More sharing options...
rybass Posted May 7, 2009 Share Posted May 7, 2009 You honestly don't want to leave a tube amp on standby for hours. It can cause cathode poisoning and issues with tube response and life. 2-10 mins on standby is all that is recommended. I'm not sure if it's causing your issue but for future thought don't leave it on standby for hours. Link to comment Share on other sites More sharing options...
Murph Posted May 7, 2009 Share Posted May 7, 2009 You honestly don't want to leave a tube amp on standby for hours. It can cause cathode poisoning and issues with tube response and life. 2-10 mins on standby is all that is recommended. I'm not sure if it's causing your issue but for future thought don't leave it on standby for hours. +1. I doubt he's caused any damage in such a short time, but. My (lifetime) study tells me power up on standby. A few minutes then standby on. Power down without, just flip off with standby on. Another thing oilpit, tube amps do make noise. They are running much higher voltage, and they are kind of noisey. I wouldn't sweat it for a while, unless it's "ungiggable". Best of luck. Murph. Link to comment Share on other sites More sharing options...
:oilpit: Posted May 7, 2009 Author Share Posted May 7, 2009 Last night I took the power amps out, one sounded like a dead lightbulb when it was shaken. Put them back in and I was having the same pop thing, then I tapped them to see if they made weird noises, which is supposedly a sign of a tube thats on the fritz (no such noise was produced). As soon as I tapped it a few times the crackling went away. Now it just sort of hums, with the odd crackle, I think I was making a mountain out of a molehill. Regardless, it will see an amp tech this weekend. Thanks for all the help Link to comment Share on other sites More sharing options...
Murph Posted May 7, 2009 Share Posted May 7, 2009 Best of luck. If it sounds good. It's good. In the '60's/'70's nobody biased anything. We went to the drugstore tube checker and checked 'em for free. The tubes were in the little doors underneath. Whoops.... That was a trade secret..... Murph. Link to comment Share on other sites More sharing options...
Riffster Posted May 7, 2009 Share Posted May 7, 2009 On the impedance, you can either match the head or go one level higher not lower. That is why is called "minimum impedance" when talking about the amp output. To me it sounds like you have a bad power tube, is it an el84? they are fragile and last only one year in theory. My Peavey amp used to crackle, pop, loose volume, get muddy and it was all a bad tube. If you shook it a rattled that is it. If it does not anymore it does not mean it is not bad anymore. Link to comment Share on other sites More sharing options...
Bluemoon Posted May 7, 2009 Share Posted May 7, 2009 Last night I took the power amps out' date=' one sounded like a dead lightbulb when it was shaken.Put them back in and I was having the same pop thing, then I tapped them to see if they made weird noises, which is supposedly a sign of a tube thats on the fritz (no such noise was produced). As soon as I tapped it a few times the crackling went away. Now it just sort of hums, with the odd crackle, I think I was making a mountain out of a molehill. Regardless, it will see an amp tech this weekend. Thanks for all the help[/quote'] Tube amps are hummers. Link to comment Share on other sites More sharing options...
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