Taking signal from mono guitar amp...?

D

Doctor Varney

Cave dwelling Luddite
My guitar amp is mono, obviously, as it only has one speaker but when I plug in headphones I get the mono signal across both cans (obviously). So does this mean it has been built with a stereo phone socket, to which the mono has been wired to both sides of the stereo socket? If so, what will be the result if I route from that headphone socket to my computer's soundcard input socket, using a single mono lead? Will I have to push it in half way to get a connection?
 
Just buy a TRS to twin TR output cable. That's a pretty standard cable for effects connections to a mixer's insert point, so most music stores or even Radio Shack would carry that. And I recommend doing that so that you don't do any possible damage to the headphone output on your guitar amp. If you've ever read a manual for a Portastudio, you'd know there's a strong warning not to plug in mono headphone jacks as it will short out that circuit.

From a fidelity standpoint, you'd be better off just Mic'ing up the guitar cab with an SM57 microphone. That way you get all the tonal characteristics of the guitar amp's speaker output and not just the electronics of it. That will be a louder way of doing it though. So if you have noise issues with your neighbors, go with the direct cable route.

Cheers! :)
 
Doctor Varney said:
Thanks. Actually I'm hoping to use it as a mic pre amp into the computer. Just as an experiment.
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That's probably a bad idea as microphones, (good ones, that is), require a balanced 3 pin XLR connection and an initial gain stage that requires more gain then a guitar pick up does. So you'll have a real gain and impedance mismatch on your hands.

Even the guitar amp's headphone output is not really designed to feed a line level input. So even your initial idea is not a great one, electrically speaking.

Ideally, what you'd want that guitar amp to have is a dedicated line level output to feed your computer's sound card line input. As the headphone's output on that guitar amp may be too strong of a signal for the computer.

You need to read up on levels and impedance matching to get a better handle on all this stuff.

Cheers! :)
 
Thanks. Your advice is noted. I'll start looking for a microphone pre-amp instead.

Most people use a USB/ Firewire interface, which usually have built in pre-amps. I'm using a Creative E-MU card, which doesn't have one. So I've been using a Behringer mixer's onboard pre's for mine. Since I'm only doing speech, I figure I could probably get away with a basic mic pre-amp and bypass the cheap mixer. While the Behringer is great for playback, it's not so good on the way in. Fine for distorted guitar with VST plugins (which I only do for fun) but all my real music is done electronically in the box, so no need to worry about external signal paths. It's just the mic signal I need to improve here.
 
I have a question though. Many of the cheaper pre-amps I have looked at feature a standard jack connection. You spoke about XLR. I do not use Phantom Power on my dynamic mic (KAM KDM400) and it also came with a jack lead. So will it make any real difference what sort of connector socket I go for, if I'm not actually intending to use Phantom power? Really, what I want to do, is get the signal up in as a clear a condition as possible before it reaches the recording software. I haven't had much success using amping VSTs - and I think that's because I was feeding in a ropey signal to begin with. What do you think?

I also worry that if I upgrade my mic (which seems sensible, I know) whether the Behringer won't do it much justice and I'll be back to sqaure one. So, for now, I was thinking stick with this mic for a while and seek a reasonably quiet budget pre amp. Am I on the right track with my thinking?

I was considering a USB mic but a few people have warned me off it.
 
Doctor Varney said:
I have a question though. Many of the cheaper pre-amps I have looked at feature a standard jack connection. You spoke about XLR. I do not use Phantom Power on my dynamic mic (KAM KDM400) and it also came with a jack lead. So will it make any real difference what sort of connector socket I go for, if I'm not actually intending to use Phantom power? Really, what I want to do, is get the signal up in as a clear a condition as possible before it reaches the recording software. I haven't had much success using amping VSTs - and I think that's because I was feeding in a ropey signal to begin with. What do you think?

I also worry that if I upgrade my mic (which seems sensible, I know) whether the Behringer won't do it much justice and I'll be back to sqaure one. So, for now, I was thinking stick with this mic for a while and seek a reasonably quiet budget pre amp. Am I on the right track with my thinking?

I was considering a USB mic but a few people have warned me off it.
Click to expand...
There are a multitude of dynamic non condenser microphones out there that make use of an XLR connector and do not require phantom power. That connector style is the standard used for balanced cable runs which reject RF interference and hum over longer cable runs over 30 feet. It is not the sole designation of a phantom powered condenser microphone, though phantom power does require a 3 conductor connection.

I'm not up on what the latest and greatest external analog to digital preamps are. So you might want to check out other sections of the forum where digital audio is discussed. Or wait for others here to chime in with their recommendations. As a general rule of thumb, the cheaper ones which don't offer balanced XLR connectors would generally not be offering up the best specs or sound quality. But for speech use, those still might be good enough for simple private use projects.

Cheers! :)
 
Maybe Im missing something...but a dynamic microphone will address the computers sound card directly, using the "mic input" on the computer. And for voice work the use of the sound card as the interface should prove adequate. That mike has XLR on it but comes with a cable that has xlr on the mic end and 1/4" phone plug on the other. You should just need an adapter from 1/4" phone to 1/8" phone which is generally the size on computers.
 
mdainsd said:
And for voice work the use of the sound card as the interface should prove adequate.
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Apparently we have different ideas about "voice work". As far as I'm concerned the mic input on a computer is not adequate for anything but Skype and gaming.
 
Well... some good points here. I have to say though, that this dynamic doesn't give out much without a pre-amp. Certainly nothing useful, as the attendant noise becomes infinitely more apparent when the waveform is normalised digitally to +00dBfs.

So if I'm going to continue using this mic, I don't think I'll be just sticking a 1/4" jack directly into the sound card. It needs something...
 
I don't think it's jack size that will be a step down, but not having some sort of pre-amp... well, I just can't seem to get a decent level in without one. Maybe a condenser would, but then I'm sure it needs Phantom Power - does it not? Or is that not always the case with condensers?
 
The 1/8" mic input on a computer probably has "plug-in power" which is something like 5VDC on the ring of the tiny TRS to power a small condenser element. I don't know what happens when you use a 1/8" TS adapter from a dynamic mic's 1/4". I would want to try it with an adapter that used a 1/8" TRS with the ring unterminated to see if it made any difference.
 
Doctor Varney said:
I have a question though. Many of the cheaper pre-amps I have looked at feature a standard jack connection. You spoke about XLR. I do not use Phantom Power on my dynamic mic (KAM KDM400) and it also came with a jack lead. So will it make any real difference what sort of connector socket I go for, if I'm not actually intending to use Phantom power? Really, what I want to do, is get the signal up in as a clear a condition as possible before it reaches the recording software. I haven't had much success using amping VSTs - and I think that's because I was feeding in a ropey signal to begin with. What do you think?

I also worry that if I upgrade my mic (which seems sensible, I know) whether the Behringer won't do it much justice and I'll be back to sqaure one. So, for now, I was thinking stick with this mic for a while and seek a reasonably quiet budget pre amp. Am I on the right track with my thinking?

I was considering a USB mic but a few people have warned me off it.
Click to expand...

Most mic pre amps you will find have an XLR input for the mic and a jack output to go to the Audio Interface/A to D converter. The good ones will have a TRS balanced jack; cheaper ones may have TS unbalaned. As for your guitar amp, those are made to perform with guitars where a bit of noise and distortion isn't usually worried about and can be actually desired as part of the sound. Behringer mixers are economy devices but I'd suspect that the mic pres in that are better than your guitar amp. I'd just keep using the Behringer until you start buying new mics, pre amps, etc.

mdainsd said:
Maybe Im missing something...but a dynamic microphone will address the computers sound card directly, using the "mic input" on the computer. And for voice work the use of the sound card as the interface should prove adequate. That mike has XLR on it but comes with a cable that has xlr on the mic end and 1/4" phone plug on the other. You should just need an adapter from 1/4" phone to 1/8" phone which is generally the size on computers.
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For me, voice work is more critical on quality than music. With a music mix, little bits of noise from the mic or sound card can get buried in the mix; with voice your recording is out there naked in all it's glory. Certainly I find the most difficult thing to get right in home studio environment is pure voice over work. Every little flaw, be it the acoustics of your room or the electronic noise in your system is plain for all to hear.

mdainsd said:
Good for you. After looking up the specs on the O/Ps microphone, I made the comment about adequate.
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The trouble with adequate is that noise etc. is cumulative so if you run a rubbish mic into a rubbish pre amp (and all built in computer sound cards are rubbish) you don't get a "match". You get double the rubbish. While a good pre amp won't improve a less than perfect mic, at least it won't make it sound even worse.
 
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