Hissing and crackling sounds

[SirChick]

I keep getting hissing and crackling sounds when my amp is on... i own a peavy 6505 combo amp... when the amp is on standby to keep the tubes warm it is fine ... it is only when i play but it isn't as noticeable as I'm playing guitar but you can notice it just about but if i turn the guitar volume right off its very clear then...

what is causing it ? =/ Is it something to worry about?

[Brad1]

Glad to see you logged in, Sir.

Kapt. here. Be patient, sometimes it takes a day or two for someone with an idea to stumble across this, and feel he has time at the moment to get into it. Also, be ready to answer more pointed questions that may help diagnose your problem.

Could be tubes or caps failing, bad BIAS...or even a bad guitar cord, bad pot or jack, bad solder joint, improper wire routing....a bunch of stuff. Depends on the noise.

Someone mo'better then me may jump in soon. I am bumping this to the top. If no answer in the next day or so, do a polite bump yourself. This is definitely the best place to ask tube amp questions. Once you get someone's attention, you'll get expert advice. Hang in there.

Brad1

[SirChick]

Ok well just to warn you I may not know some of the terms so may need to be patient with me..

But for further infomation i tested my 15 watt amp and that plays fine so the cables/guitar/pedals are fine so it must be amp related.

[Brad1]

See...you've already done the first obvious step in troubleshooting...eliminating possible suspects!

Will generate fewer questions later. BTW, next step is to unplug the amp, and reseat all the tubes, one at a time. See if there is any corrosion on the pins. BE CAREFUL in there! While not likely to get buzzed with the chassis still mounted, those big caps hold a dangerous charge. Just don't let both hands touch metal at the same time, and don't do this while your soaking in the hot tub. (You may have to spread metal tube clamps, if that amp has them).

After, turn it back on, and see if it is any better. If not, probably best to NOT leave it on for long until you solve the problem. Output tubes are expensive enough...if you blow that output transformer, you'll be quite sad.

Brad1

[SirChick]

I'd have to take it to a shop to do that.. theres no way I'm going to be able to do that or have the courage :P

[rf7]

Most likely it's a noisy preamp tube. If you want your amp to be quiet, have someone check it out for you.

[Brad1]

I'd have to take it to a shop to do that.. theres no way I'm going to be able to do that or have the courage :P

With the amp unplugged, you very likely won't get a shock simply pulling and inserting tubes. That warning has to be there to make relative novices aware that that there can be lethal voltages stored in these things, even when unplugged. It's good to have a healthy fear to keep you on your toes. The reason for not touching metal with both hands is that it is possible in some cases to run high voltage from one hand to ground in the other...and it goes right through your chest...where the ol' blood pump is.

An amp tech may be likely to swap those preamp tubes with the thing powered up, but a good amp tech is always aware. It's just a good habit to get into to not touch both hands to metal when messing with these things. "one hand in your back pocket" is an old adage, though few people actually do that. You may get a jolt even from one hand touching something live, but it won't be quite so dangerous as going through your body.

It's probably a good idea for you just to take it in to someone. It may be just a noisy preamp tube, and that won't cost you much. Plus someone worth his salt would probably give it a good once-over anyway, clean the pots and connectors, and make sure everything else is ok. If it's something worse, well, you'll probably be unlikely to know what to do, anyway. So...

Since you do have a tube amp, you may just want to browse posts in here to learn more about them. Eventually, you may learn enough to do simple diagnostics and maintenance, and feel confident you ain't gonna curl your hair doing them.

Didn't mean to make you nervous, but in the case of high-voltage guitar amps, nervous is better than dead.

Brad1

[SirChick]

What if i wore rubber gloves ?

[Enzo]

If you are that afraid of it, then please take it to someone qualified to work on it. There is no shame is saying, "whatever this needs is beyond my experience."

[SirChick]

There is that fear of being electrocuted to death but I do also really want to learn how to keep amp's maintained rather than a show having it all weekend to then charge me lol :P

[Brad1]

There is that fear of being electrocuted to death but I do also really want to learn how to keep amp's maintained rather than a show having it all weekend to then charge me lol :P

It's really simple. Do some research about safety precautions when messing with these. Don't do it when enebriated, and don't mess with them if you are distracted by the porn flick. Don't lose the healthy fear and respect, but don't mess with them if you are so fearful your hands are shaking or your mind is racing.

If you want it done now, take it to someone. In the meantime, do some research if you would like to learn how to do things, but don't try it until you are comfortable in knowing what is safe, and what isn't.

Always research the particular amp you are working on before you even consider messing with it. Some old 50's tube amps have a hot chassis. (I have a Supro with one, your's doesn't...or shouldn't unless something went terribly wrong).

Nearly everything you need to know can be found by searching.

A simple tube swap SHOULDN'T pose any danger, but anytime someone claims it won't happen, something can happen. Practice simple-to-comprehend safety procedures, and your chances of frying are decreased to almost nothing. Almost.

I led you here because these guys know what they are doing. rf7 suggested a noisy preamp tube, and since nobody disputed that, or added to it, I'd say that's a good bet. It shouldn't take a week for someone to pop in another tube to try. It will take a few minutes, unless they find something else. And, they'll still likely charge for an hour, and for the inexpensive tube.

OR, you could go buy a preamp tube or two, and replace them to see if it cleans it up. Pop one out, pop the same thing in...turn it on. If that doesn't fix it, then you at least have a spare tube or two.

Just don't try that with output tubes, though, at this point. Those may need adjustments that are obviously beyond your grasp, at present.

So, there ya go. It's basically pretty simple. Now, quit being pesky, and decide what you need to do

Brad1