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Amp Hiss

Postby Terry Nutkins » Thu Apr 24, 2008 10:51 am

Hi there,

I am looking to eliminate/suppress hiss from my amps, as it is adding a lot of unwanted noise to recordings.

Amps in question:
2x 100W Peavey Bandit tube amp
20W Marshall practice amp

All emit a generic hiss when turned on: even without any input (and with all levels turned to 0). When an instrument is plugged in and the gain is turned up, the hiss increases accordingly.

All amps have been serviced recently, but if I recall, they all had this problem straight out of the box; it's only now that I'm recording with them that it has become a real issue.

The hiss received through a mic when miking the amps is greatest around the amp's centre and gradually dissipates with distance (and with the mic's angle). Obviously this doesn't bode well for close-miking...

Could anyone tell me where the problem(s) lie?

-Is it a generic design flaw of the amps?

-Could it be related to the room's power supply?

-Is there any kind of external equipment that could be used to ameliorate the problem?

-Could EQ/compression via the mixer (01v96) help in a way that won't negatively affect the amp's tone?

Thanks...
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Re: Amp Hiss

Postby Arpangel » Thu Apr 24, 2008 11:02 am

You just have to live with it, it's inherent in their design. I have a couple of noisy guitar pre-amps, and effects, you need to interfere with them as little as possible, so I just use a gate set to a long release time (please experiment with this) if you get this just right you can get rid of most of the noise, but you have to careful, as the noise constantly disappearing and reappearing can be even more distracting than the noise itself ! I would not compress or EQ, just use the gate and and leave it at that. Unless of course you want the EQ or compression to be a a part of the sound.

Tony.
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Re: Amp Hiss

Postby Henry-S » Thu Apr 24, 2008 12:00 pm

When amps get cranked up they hiss. Just been in the studio last few weekends with my amp being in a dedicated amp room and you always get hiss.... but this is gated out usually when not playing.

You could maybe use an eq to help the hiss but I think that your best bet is just live with it. When playing the guitar through the amp you shouldn't hear a hissing because the hissing should be well below the output of the amp. I find that the hissing will be more noticable if you don't have the amp loud enough so make sure you are getting it loud.

Power supplys will often give a different sound because I had this again in the studio my guitar amp has a

sssssssssssssssss sound and when I had my PODXT powersupply plugged into the wall and then put the power supply near my guitar it turned from an sssss to an mmmmmmm sound. We just unplugged the supply and when we needed it made sure I was not in the same room.

I would go around and check if you got any adapters because my single coils are replacements (bareknuckle pickups running hotter than standards) so they pickup even more noise... but the sustain and punch on the pickups is more than worth the extra noise.

But yeah amps are noisy mate, nothing you can really do about it. I suppose you could try noise cancellation like recording the sound of the hiss and then running it back into the system... but I have never tried that before so not sure how good the results would be? I think you might have to live with it though... Brian May has hiss and he sounds bloody lovely :)
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Re: Amp Hiss

Postby Arpangel » Thu Apr 24, 2008 12:44 pm

Henry-S wrote:

But yeah amps are noisy mate, nothing you can really do about it. I suppose you could try noise cancellation like recording the sound of the hiss and then running it back into the system... but I have never tried that before so not sure how good the results would be? I think you might have to live with it though... Brian May has hiss and he sounds bloody lovely :)


Or in your DAW, if you have a good noise reducer you can sample a bit of the hiss and let it filter it out automatically, can work sometimes, but the side effects can be awful so be careful. But so called noise is often an essential part of an instruments sound.

Tony,
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Re: Amp Hiss

Postby Terry Nutkins » Thu Apr 24, 2008 1:04 pm

ha, I feared as much. stupid question I suppose but my amps do seem particularly noisy. I appreciate the value of noise; but at the moment my tracks (especially acoustic/clean stuff) are drowning in it.

I will try messing around with the gate tonight, thanks chaps...
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Re: Amp Hiss

Postby mhaigh » Thu Apr 24, 2008 1:18 pm

acoustics should be close miked with a condensor or two, no amps - for clean i'd DI and use software fx or an fx unit with amp sim...
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Re: Amp Hiss

Postby Studio Support Gnome » Thu Apr 24, 2008 1:35 pm

typically people who find this a serious issue, are running the amps with the master level turned down, so the effective difference in level between the natural background noise, and the actual guitar tone is much smaller... thus when recorded, the hiss appears huge...

if you turn the amp master volume UP , the hiss due to it's power stage gain won't get any louder , as the amplifier "proper" is actuall running flat ut all the time... the master volume turns the INPUT to the powerstage down, NOT the output... to quieten an output you have to use something akin to a "Powerbrake"

but pre-amp induced high gain hiss , as when using loads of distortion, definitely WILL get louder.... a balance needs to be struck... typically players find they need less gain when the volume is cranked up!

the noise gate idea works to keep the pre-amp noise under control, but needs careful setting up... or you can end up with a nasty "stop start" sounding tone...


the Boss NS50 is ideal, as it triggers the gate from the guitar's clean output , which is then fed to the amp... then the pre amp output comes back to the NS50, is gated accordingly, before being sent back to the power-amp input.

what that means is that when you're not playing, the amp is gated, but the moment you actually makea noise with the guitar the gate opens .... obviously the sensitivity is controllable... but it's alot more useful for guitars than a normal noise gate as found in Compressor/gates

it's sadly only useful for amps that have a series, or insert style facility , FX loop in some cases... not all are created equal... parallel loops are useless for this....

(the same is true for the most appropriate use of a normal compressor/gate)

for easily found budget solutions, actually, i found the behringer composer to work acceptably in a live gig scenario... but I wouldn't use it in the studio like that...

seek ye out a Boss NS50.

or equivalent thereof...


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Re: Amp Hiss

Postby Parker Fly » Thu Apr 24, 2008 2:03 pm

Terry Nutkins wrote:Hi there,

I am looking to eliminate/suppress hiss from my amps, as it is adding a lot of unwanted noise to recordings.

Get a Rocktron hush; I use one, as does a friend (on his seashore Marshall DSL50's) and they'll remove said hiss without colouring the sound.

You can get them from the US for about £30, or £50 in the UK, and they have an adjustable threshold too.
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Re: Amp Hiss

Postby Arpangel » Thu Apr 24, 2008 4:59 pm

He he ! there's noise and there's noise, some amps are so quiet, but my friends Mesa Boogie is on another planet, when he switched it on it was like a very noisy thing that had gone to university and studied very noisy things and got a PHD with honors in very noisy things !

Tony.
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