Amp troubles/unwanted noises

[Always Broke]

Hey experts,

Might be overkill to consult you guys, but my Peavey C30 has been making a lot of bad noises lately. Whenever it would start up, as the tubes warm up the thing produces all kinds of loud buzzing and rattling, then maybe it will eventually settle to be playable. Otherwise, it's always noisy, the volume and tones change, and it's just a plain ol' pain.

I was wondering, might it be a humidity thing? Do I need to get a new set of tubes? Is it a bigger amp problem? At any rate, I just wanted to know if there was any potential for serious damage that I need to be aware of, as well as solutions on how to fix the problem.

If you guys can spare me a few lines, it would be much appreciated!

[BubbaVO]

If you guys can spare me a few lines, it would be much appreciated!

Sometimes you have to open it up and check the PCB meticulously. One time I went in disturbed by the noise the amp was making and discovered that there was something missing .... my chops.

Thank you. Please tip your waitress.

[whiskeyzulu]

Does the noise go away completely once warmed up? Does amp have reverb & do you get the noise w/ the reverb off?

Did you check to make sure all tubes are well seated in their sockets and then gently tap each tube with a pencil - you'll hear if the tube is microphonic and should be replaced. If tubes appear to be good you can also try spraying electronic spray cleaner on pins. Also, removing the phase inverter tube allows you to determine if its pre-amp or power tube section. Good luck and if the problem continues you should also check out the peavey forum -

[Always Broke]

Does the noise go away completely once warmed up? Does amp have reverb & do you get the noise w/ the reverb off?

Did you check to make sure all tubes are well seated in their sockets and then gently tap each tube with a pencil - you'll hear if the tube is microphonic and should be replaced. If tubes appear to be good you can also try spraying electronic spray cleaner on pins. Also, removing the phase inverter tube allows you to determine if its pre-amp or power tube section. Good luck and if the problem continues you should also check out the peavey forum -

One of the EL84s is microphonic, and looks like it's running a bit hotter than the rest. Do I need to replace just that one, or the entire set?

The volume and tone are everywhere now, and just noisy as hell. Any more suggestions?

[gtone]

While there are any number of issues which could result in crackling/popping noises (faulty tubes, resistors, caps, controls, jacks, circuit boards, cords/cables/connectors, etc.), replacing tubes is so simple to do, this'd be the logical first thing to try. Hopefully, you have a spare set of power and pre-amp tubes around; if not, you'll need to find some as you'll need them eventually.

Sounds like your power tubes need replacing anyhow, as you've indicated that one is microphonic and is maybe running hotter, but I'd also be suspicious of the pre-amp tubes, as crackling noises are often experienced as these wear out. Some amp designs/circuits require biasing your power tubes, others do not, so you might want to check your owner's manual or with Peavey to determine whether this is applicable.

[seeker]

To clarify, unless you know someone with a power tube tester and an ample tube supply, you'd need to change all the power tubes. They are sold as matched sets; in your case it would be a quad.

The Classic 30 is indeed fixed bias (meaning that bias is -not- self adjusting as in cathode biasing) with a resistor (no pot). However, from what I've read, the consensus is that the factory build is cold biased, so any set you buy will work in the Classic 30.

However (disclaimer) I would still contact Peavey for their advice.

Oh yeah, and +1 on trying diff preamp tubes.

[landon w]

the easiest way to do this is just buy your preamp tubes, and remove them one at a time until the noise goes away. this way you locate the bad tube and dont have to replace all of them at once when there is no need.

then youll have some spares

popping, crackling, hissing, humming, is preamp tubes NO DOUBT. Powere tubes will generally just give you less volume and presence when getting old.

easy easy fix.

[Brewmaster]

popping, crackling, hissing, humming, is preamp tubes NO DOUBT. Powere tubes will generally just give you less volume and presence when getting old.

easy easy fix.

Well, I would say 85-90% of the time. Other component failures give similar symptoms. I had one come in with a loose wire on the tube socket that gave the same symptoms.

When it comes time to order new EL-84's JJ are work horses, TAD are highly recommended. If you order from Tube Depot request the bias point at about 24 ma but anywhere from 24-28 work really well in the Classic 30.

[gtone]

How'd you make out with this? Did replacing the pre-amp tubes solve your problem?

[Always Broke]

Thanks for the input guys. I replaced the EL84s, and the annoying fart/feedback howl was gone, but there is still some annoying (but nowhere near as bad) crackling going on. Playing pretty much drowns it out.

I also observed the power tubes glow blue in some places, and there seems to be a corelation with the hissy noises. When the hissy noises go, so does the blue tinge (will try to get pics up)

[gtone]

I'm still betting the crackling is coming from the preamp tubes. Change those out and see what's up. Again, my two cents...