#1
my amp is making an AM station hiss. what could cause this. my pre and post gain are turned down to 0. I unplugged my foot switch and it stopped but it was a coincidence. it started getting more and more distorted then woosh here comes the hiss.
#2
Possibly a preamp tube going bad.  How old are the tubes in there?  

For what it's worth my 5150 always had a background hiss to it - had to put a noise gate in the loop.  
Guitars:
Jackson Kelly KE3 - MIJ (Distortion/Jazz)
Jackson DKMGT Dinky (EMG 81/85)
ESP E-II Eclipse Custom (JB/'59)
ESP LTD EC-1001FR (EMG 81/60)
Fender MIM Strat

Amps:
Mesa/Boogie Dual Rectifier Roadster 212
Laney IronHeart IRT-Studio
Peavey Vypyr 30
Peavey ReValver Amp Sims
TOOOO many T.C. Electronic Pedals. . .
#4
I'm by no means an expert on this, but isn't poor shielding in the cables a typical cause of this. Have you tried using a different lead?
#5
Where I rehearse there's a problem with power in the building. Mesa amps for exmple (and only Mesa for that matter) pick up a latino radio statio. 
Putting a noise gate on it fixes it. Interestingly enough - Marshall amps don't pick up that station, they just pick up noise.
#6
With the amount of gain these amps produce, some degree of hiss just comes with the territory. But you need to give us more information.

What kind of guitar are you using and is it internally shielded? Are you sure you don't have any ground loops? Does using the effects loop affect the amount of hiss you're getting?

Turning down the pre and post gain to zero and still getting hum doesn't make any sense. How can the speakers generate hum if you're not powering them?
Quote by TheSennaj
And well yes, I'll enjoy the carpal tunnel and tendonitis, because trying to get one is clearly smarter than any word you have spoken thus far.
#7
Quote by diabolical
Where I rehearse there's a problem with power in the building. Mesa amps for exmple (and only Mesa for that matter) pick up a latino radio statio. 

That's funny that you say that. My buddy's single rec would do the same thing sometimes at practice. Always made us laugh. 
#8
Same as above, there is SOME hiss to these amps, especially the more post you give it.  Poor electrical / grounding with the wiring you're plugged into can cause it, or a tube going bad, or already bad.  So basically everything that was already stated.
#9
pwnsauce090 unfortunately new doesn't mean good with tubes.  Since this was just shipped I'd reseat all of the tubes first.  

Again there is some background hiss in these amps. 

Did you buy new or used/refurb?
Guitars:
Jackson Kelly KE3 - MIJ (Distortion/Jazz)
Jackson DKMGT Dinky (EMG 81/85)
ESP E-II Eclipse Custom (JB/'59)
ESP LTD EC-1001FR (EMG 81/60)
Fender MIM Strat

Amps:
Mesa/Boogie Dual Rectifier Roadster 212
Laney IronHeart IRT-Studio
Peavey Vypyr 30
Peavey ReValver Amp Sims
TOOOO many T.C. Electronic Pedals. . .
#11
I plugged the effect return loop and it stopped so I switched my tubes around. then it came back but not  as bad. but now it has a hum like a low feedback hum.
#14
it's probably a bad  tube . My peavey did something similar. It was scary I thought the thing was going to blow up or something. turned out one of the preamp tubes was bad so I swapped it out with a new one.. Would cost 10 -15 bucks to replace... assuming it's just 1 of the tubes. 

Downside to tube amps.... they require better care and more maintenance than solid state amps.
#15
Quote by pwnsauce090
T00DEEPBLUE I'm using a Ibanez rg 7 string. I don't know how it still hums turning it on standby also stopped it. could it be a speaker issue.

Speakers cannot generate their own hum.

Another possibility is that you're using very dirty voltage going to your amp. The supply from the wall outlet might not be very well grounded. To which the solution to that is getting a power conditioner. Another thing to realize is that these amps are inherently noisy at high gain settings anyway, because they can produce so much gain. So some of that noise can be accounted for by just being a quirk of the amp's design.

Microphonic tubes also create noise. Just because an amp is new does not mean that it doesn't have a bad tube. Tubes can last anywhere between 30 minutes to 20+ years, just by the way they were manufactured.
Quote by TheSennaj
And well yes, I'll enjoy the carpal tunnel and tendonitis, because trying to get one is clearly smarter than any word you have spoken thus far.
#16
I swear by power conditioners.
WTLT 2014 GG&A

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youre just being a jerk man.



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