Need help with a guitar amp noise (hum, hiss, buzz)

[Staley8]

Hi,
I stumbled on this site and am hoping some experts here can point me in the right direction. My problem:

So I have a Marshall vs65r amp. It's a 65watt amp with a single 12 inch speaker in it. Solid state power amp and a tube preamp. Whenever I have this on now I get a sort of hum. Almost like it's a ground hum/buzz. I tried different outlets, different guitars and different cables. I've tried a 2 to 3 prong adapter but can't get rid of it. One clue might be that it doesn't start to hum until about 2-3 seconds after I hit the power switch. Which could mean that it has to do with the tube pre-amp warming up and humming

OK, I start it up with nothing plugged in, no cables or anything. I get little or no hum/buzz/hiss. When I plug in a cable/guitar I start to get a hum. The louder I turn it up the louder the hum gets. When in overdrive mode it is very noisy and humming.

Is my tube bad? Is my power supply bad? Am I bad?
Thank you very much

[Insaneogram]

I might just add to the question if you don't mind...

How do you know when it's time to change tubes? My JCM2000 crackles now whenever it's turned on whether there's stuff plugged in or not so I guess it's tube-time?

[Outlaws]

Tube amps are inherently noisey and do produce a cerntain amount of hum. Its definately something your have to get used to after coming from solidstate.

I can't really say if its beyond normal other than go to a store and play the same amp with the same kind of guitar and see if thats it. It might just be single coil pickups or it might just be that it isn't really ground. Not all outlets that are 3 prong were ever ground. I found that out by tearing out the face plate (after turning off the breaker) and adding the ground that the lazy ass home builders never conencted.


As for crackle...that is something to look into.

[gitrguy87]

I could also be that your guitar input isnt grounded.

[Staley8]

well I've tried the amp at two locations, with multiple guitars, on multiple circuits, with/without a 3-2 prong adapter. I realize there will be some hum, but it was never this bad before, now it is much worse. I'm at a dead end here.

[SteveK]

Is it the same with both single coil and humbucking pickups?

[spoonie g]

yeah, I've often wondered how recording engineers combat this problem. I'm going to be going into the studio soon and my favorite guitar is a les paul w/ p-90's, but it buzzes like crazy!

[Staley8]

Originally Posted by SteveK

Is it the same with both single coil and humbucking pickups?

Ya, it's the same for both. In fact even with the cable plugged in and no guitar attached to it it still hums/buzzes. It didn't use to do this and I've always used the same guitar/cable and have tested with other amps and they work great. I have a feeling it's a wiring issue in the amp (I'm hoping it's just a tube but would a bad tube cause this or would a bad tube be more crackle and pop?)

[Thurgood]

Sounds like the tube (12ax7a) has gone south. Check your manual to replace or get tech. Tubes are cheap. My friend had this problem and a change of pre-tube solved the prob. Note: the tube on that model is pretty hot so any failure will be quite noticable. How old is amp? How hard do you drive it? Bet it is the single tube pre.

[Staley8]

Originally Posted by Thurgood

Sounds like the tube (12ax7a) has gone south. Check your manual to replace or get tech. Tubes are cheap. My friend had this problem and a change of pre-tube solved the prob. Note: the tube on that model is pretty hot so any failure will be quite noticable. How old is amp? How hard do you drive it? Bet it is the single tube pre.

Yup, it's a single tube in the pre-amp and a solid state power amp. The amp is probably 2-3 years old. I can't say I drive it real hard, but I play through it quite a bit and it puts on some travel milage (sometimes in my trunk ) 2-3 times a week for a year or more. If anything there could be damage to the tube?

I do not know the brand of that tube, but the model of the tube that fits is "12AX7 preamp tube" --- http://www.tubedepot.com/12ax7.html . (In fact it might be this exact tube: http://www.tubedepot.com/jj-ecc83.html )

edit: I forgot to mention it seems to have lost some of it's punchiness too. could be in my head though

[Sloan]

I had an old Fender Princeton Chorus amp that developed a very, very loud hum over the years. So, I just took the thing apart and poked around until I found out what components the hum seemed to be originating from. Turned out that one of those huge-ass capacitors was starting to come loose so I just needed to resolder it. Bam, problem solved.

[kevinkPRS]

Hello Im kinda haveing the same problem.But my problem comes and gos.When i first tun on the amp it plays fine.Later on as im playing out of no where the amp pops the crackles really loud,but gos away when I turn it off then turn it back on.Could this be a bad tube?The amp is a B 52 Stealth seires.My guitar is a Prs with EMG active humbucks.The pickups dont need to be grouned with active humuckers so I dont think its that.All the tubes light up but could it still be a tube going out?I bought the amp used so not really sure how hard it was played.Ive had it about 6 months now and havent really pushed it sinse its so loud.Oh yea it did pop and like cut out and sound was real low for like 30 ceconds then made the horrible cracklin noise.Any info would be appreciated Thanks and keep ROCKIN

[TyphoidHippo]

Originally Posted by Staley8

I do not know the brand of that tube, but the model of the tube that fits is "12AX7 preamp tube"

It doesn't matter the brand...any 12AX7 will work - in fact - now would be a great time to do some research on the different characteristics of all the different kinds of 12AX7 tubes - there's quite a few of them, and it's almost certain that with that many different flavors of tubes, there's at least one out there you will like better than the original, anyway. Good luck finding it!

edit: I just noticed that this thread is 3 years old - hahahaha....oh man....

[grafixguy4point]

Originally Posted by spoonie g

yeah, I've often wondered how recording engineers combat this problem. I'm going to be going into the studio soon and my favorite guitar is a les paul w/ p-90's, but it buzzes like crazy!

use a gate. seriously. thats about it. if you gate the guitars right and get your mic placement right, and (sadly) your EQ done up just so, you should be virtually buzz-free in studio.

now live, thats your problem. lol.

[antoinesguitar]

Hi Staley8

I don't know if your still having that ground loop issue, but I am having that problem mostly at a club that I perform at. And I have had all types of tube amps at this club. Something that I know is a problem is the club need's to put in isolated grounds on the stage ac outlets. Which we would be hard pressed to convince them to have this done. Even then it may not eliminate all of the 60hz hum, but it should cut it down substantially. If your using your amp at home you could have a electrician put in isolated grounds. I have tried those hum eliminators and their hit or miss! I real good noise gate works, but it has to be a good one with more than just decay, and threshold. The one's in the high end rack units are much more comprehensive. But it would be nice if someone would come up with something the give's musicians a good clean condition power source as well as a temporary isolated ground.

[ggunn]

Originally Posted by antoinesguitar

Hi Staley8

I don't know if your still having that ground loop issue, but I am having that problem mostly at a club that I perform at. And I have had all types of tube amps at this club. Something that I know is a problem is the club need's to put in isolated grounds on the stage ac outlets. Which we would be hard pressed to convince them to have this done. Even then it may not eliminate all of the 60hz hum, but it should cut it down substantially. If your using your amp at home you could have a electrician put in isolated grounds. I have tried those hum eliminators and their hit or miss! I real good noise gate works, but it has to be a good one with more than just decay, and threshold. The one's in the high end rack units are much more comprehensive. But it would be nice if someone would come up with something the give's musicians a good clean condition power source as well as a temporary isolated ground.

What do you mean by "isolated ground"? I'm pretty sure that as per the NEC2008 code, the neutral and ground conductors are single point bonded at the load center and connected to the AC earth grounding electrode.

[Armistice]

Originally Posted by antoinesguitar

Hi Staley8

You know I don't think he's still around... he only ever asked the one question, 4 times and no-one's heard from him since..

And look, it's your first question too...

Go looking for old posts much?