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guitar amp hiss

hi there! sorry this seems like such a silly question - i've been in a few recording studios and all of them seem to have been able to do what I can't, so I know i'm doing something very stupid here:

i am trying to record my electric guitar by putting a Shure sm57 about 2-3 inches away form the centre of the grill cloth, running it into a Behringer UB1204-PRO mixer, which then goes into my iRiver mp3 player (which records with line-in.)

I have been told that you get a good amp sound by pointing the mic at the speakers, but when I do this, no matter how much or little gain I apply at any stage, there is definitely a noticeable hiss coming from the speaker. I think that I am not mistaking this for hiss from improper gain structure, as I have tried nearly every combination my setup allows. It is also not the mp3 player, as I have listened with the headphone output on the mixer, and the hiss is definitely there.

I also know that electrical components do give off hiss, however my teacher (who has made very good recordings with me) used the same setup as me: a microphone pointing at an amplifier running into a mixer, with perfect results.

am i placing the mic in the wrong place after all? does the amp need to be louder (i use a small marshall 15 watt amp, never tuning it up past the 3rd volume notch) or is there anything else wrong that i am doing?

thankyou for taking the time to read this long rant,
from me!


Pro Audio Guest Sat, 04/07/2007 - 00:57
thanx for the info. i realise its the amp thats making the hiss, but also that I am increasing the hiss dramatically by having the gain up very high. however, decreasing the gain means that i can't hear what the guitar is playing! (there's always a catch.......)

so...... i'm going to have to try increasing the volume of the amp, then 1)use less gain so only the stronger signal is recorded, leaving the hiss out or/and 2)position the mic further away, as when I play normally i can never hear a hiss - it's only when I get up close to the amp (or when the mic is closer to the amp?) that i can hear hiss.

if that doesn't work i will have to use a noise gate or edit it with audacity or something like that.

thankyou for the info again - if there is anything else you'd recommend please let me know!

Boswell Sat, 04/07/2007 - 04:17
If you turn the amp gain down, you will have to turn the mixer gain up by a corresponding amount to get the same recorded level, so the hiss in the recording will be much the same.

You should use an amplifier volume that you are used to and comfortable with as a performer, and mic it at that level.

For the noise, gating the channel sounds like the best practical option in the circumstances.

Kapt.Krunch Mon, 04/09/2007 - 03:50
Lethargyfred wrote: i have yet to investigate noise gates, but i am satisfied with the sound i have recorded so far.

Keep in mind how a noise gate works. If the noise IS generated from internal amp hiss, a noise gate in the guitar-to-amp chain won't quiet it. It will only cut out noise before the amp. Hardware noise gates are most effective before guitar amps, and were really useful for hiss removal of tape mixdowns. With software noise reduction programs, and software editing, hardware boxes CAN be useful, but not entirely necessary.

If you run it in the mic-pre-computer path, you need to be careful there, also. Say you have it right before the computer interface. If you are running reverb or delays through your guitar amp, it's liable to cut off the tails of the reverbs, or could chop up the delays. If you hold a note or chord for a long period, it could chop off the end of it. Set too high, it could chop up everything between string hits.

A simple explanation is that a noise gate shuts down the signal when the signal level goes below a set threshold that you set with a knob. These are touchy devices. Some compressor/limiters have built in gates. There are outboard units like the Rocktron HUSH. The HUSH is most useful in a signal chain after noisy devices like compressors or distortion pedals that generate hiss, and to cut out the noise from neon beer signs, etc. But, you would generally place any time reverb/delay pedals after them, if your amp doesn't have an effects loop.

Sounds like you got it less noisy, but it may be impossible to remove ALL the noise. You may be best off just recording that noise into a computer with the signal, and then TRYING a little bit of light noise reduction with a software program. You have to have a second or so of that noise to sample so the noise reduction program knows what to remove. And, that's only necessary IF the noise is objectionable while the guitar is playing...underneath the guitar signal.

If the noise is NOT objectionable within the guitar signal, just do a bit of hand editing. Just highlight the sections where there is no guitar playing, and change the volume to zero, or cut the part out...making sure you specify to leave the remaining sections in place. Do this BEFORE you add any reverbs or delays or anything else that lengthens that part. That way,
you're not reverbing noise at the tail end.

Noise gates can be tricky. Experiment, but be aware that they can make things choppy, can freak out your attack, or cut off tails.

I'd say, do what you can to get is as quiet as possible at the source, record that, do a little light noise removal in software IF necessary, then edit out everything in between. And, instead of just cutting the end of a section right off, you may want to fade it out to 0...especially if you have any room ambience recorded. That way it won't sound so abrupt.

Others may disagree, or expand on this. This is pretty much what I do. I stress LIGHT software noise removal, because that stuff can really futz up your careful with that.

And, as mentioned before, make sure everything in the chain allows you to get a nice clean level recorded. Too little here can add more hiss there, too much here can add distortion there.

One more thing. If you have a compressor/limiter somewhere in the chain, that could add hiss. What a compressor/limiter does is bring up low signals and bring down high signals so they are somewhere around even..depending on the settings. This means that when nothing is playing, a compressor may attempt to raise the level of any hiss present at its input, then when you hit a string, the hiss lowers while the guitar sound takes over. If you have a compressor in your guitar signal chain, listen carefully to any hiss present while not playing, strike a note, and listen as the note fades away. Does hiss gradually increase while the note decays? The compressor is may be set too high. This is actually where a lot of guys might stick a noise gate in...if they wanted to get that quacky guitar sound.

Tweak away!


Kapt.Krunch Fri, 04/06/2007 - 03:37
Is it the amp or the signal chain?

Set the amp to the volume you want to record, and put your ear where the mic is. Is the hiss there? If it is, that's where it's coming from.

Which doesn't mean something else ISN'T adding more.

Turning up the amp MAY just turn up the hiss. Try it. Does it? If it doesn't, turn up the amp, and perhaps turn down something in the signal chain for recording.

Is the hiss objectionable while the guitar is playing, or is it only noticeable in quiet sections? You can do one of three things.

Use a noise reduction unit like a HUSH, or a gate in the recording chain. This leaves the noise in the background while the guitar is playing, but shuts it down when not playing.

Record all the noise into a DAW, and remove it during quiet passages by using a software program such as a gate, or silence the quiet passages by hand. The noise will still remain in the background while the guitar is playing.

Record it into a DAW, and use a noise reduction program. Generally, you'll take a short section of nothing but the noise and make something like an FFT file. That analyzes the noise, and then you apply that algorithm to the entire track. the idea is that it removes, or at least reduces, that same noise inprint throughout the file...even during the guitar passages. Used carefully, it can get rid of a lot of stuff. Used carelessly, it can mangle the sound. If you did a bit of light removal, and then silenced the quiet sections, a lot can be done.

There are a lot of recordings that have amp hum and hiss in them while the guitar signal is there. It's just "masked" by the louder signal of the recorded instrument, and removed between passages.

Could be that it is the recording signal chain. Have you learned and set proper gain settings? If you have something set at too low output going to the next stage input, you are boosting the input to make up for it, which will probably add hiss.

If you have something set too high output going to next stage input, you'll probably have distortion.

It almost does sound like amp hiss, maybe also a bad gain staging exacerbating the situation. Try positioning the mic a bit differently...maybe at an angle a bit. Maybe it won't get the full-on straight hiss signal? Who knows. Try all kinds of stuff.

Do you have pedals plugged in, and are they causing hiss? (A lot of distortion pedals are notorious for that when distortion is turned up high). Turn the distortion of them down a bit? If they are set so high they cause hiss, they are probably too tweazy for a good recorded sound anyway...unless you like indistinguishable bumble-bee tone.

The point is, start at the source and find out where the noise starts. Then deal with it there, if you can. If you simply can't get rid of it, get a better amp (or other device) that doesn't cause it. Or, record it and deal with as best as possible later. A lot of people recorded some pretty gnarly tones that contained a bunch of noise, but they dealt with it. Sometimes you just can't get rid of all of it. All you can do is hope to mask it enough that it's unobjectionable.

Hope this helped. I'm sure there are other things I forgot to mention. :wink:


Boswell Fri, 04/06/2007 - 07:19
Problem diagnosis in stages:

Stage 1: Does the hiss change when you switch off the guitar amplifer? If it goes away, it's the amp - goto stage 2. If it doesn't, it's the mixer and/or the iRiver - goto stage3.

Stage2: Can you record with the amp louder and the mixer input gain turned down a bit? Can you use a different amp?

Stage 3: does the hiss volume change with output level settings on the mixer? If yes, it's the mixer, if no, it's the iRiver.

Come back with the results and we may be able to advise further.