Do in-amp modeling artifacts come through if you mic the amp?

S

SweetDan

New member
Let me explain one possible setup I use, in case the title of the post is hard to grok.

I have a Vox Valvetronix guitar amp. It has built-in amp modeling for several (11?) different "real" guitar amps and cabinets. (The amp itself is a small-ish 30watt combo).

If I mic up my amp, will any artifacts of the amp modeling come through in my recording?
 
gecko zzed said:
If my name was Dave, i.e. short for David, it would be Dave.

But others would make it Dav.



Some people might have settled on "mic", and so had I for a while. But after further research, I retracted and reverted to "mike".
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I rode my bic to pickup my mic. I like bicing, and in my studio I like micing. Oh wait a minute, we're not starting this one again, are we? ;)
 
dainbramage said:
What exactly do you mean by "artifacts"?
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I am assuming that since it's a modeling amp, the sound it produces is based on digital manipulation of the signal (i.e., not analog reproduction of the signal), or maybe even samples. I'm also assuming that the computer in the modeling portion of the amp puts out the modified signal (or samples) at some rate and bit depth (probably 44.1khz @ 16bits).

So, if I record the sound at a higher sample rate and depth (e.g., 96khz @ 24 bits), will my recording have "choppiness" or holes in it?

All this stems from the fact that I know the modeling amp doesn't sound as good as a "real" amp, and the only other alternative I have at the moment is to run an ITB amp sim. Either way my recordings will be of a simulated amp, and I'm trying to determine which would produce better results. (Note: I don't want to start the periodic flame war of amp sims vs. real amps...didn't we just do that a couple of months ago? ;-) )

UPDATE: I checked my amp's specs, and it samples at 44.1 k @ 24 bits.

UPDATE 2: So, what I'm really asking is "Why do my ITB amp sims sound better than when I mic my modeling amp?", since they're both "fake" anyway?
 
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SweetDan said:
So, if I record the sound at a higher sample rate and depth (e.g., 96khz @ 24 bits), will my recording have "choppiness" or holes in it?
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However the amp does its simulation, it ends up as an analog signal to drive the speaker. When you stick a mike in front of the speaker, what the speaker delivers is what the mike will hear. So the quick answer is "no".
 
SweetDan said:
UPDATE 2: So, what I'm really asking is "Why do my ITB amp sims sound better than when I mic my modeling amp?"
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One explation is that you have neither the mic, room or recording ability to get the best result from miking your amp - you haven't mentioned how you've tried this?
 
Armistice said:
One explation is that you have neither the mic, room or recording ability to get the best result from miking your amp - you haven't mentioned how you've tried this?
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I'll post some examples and descriptions of the setup soon; not at the right computer at the moment.
 
gecko zzed said:
However the amp does its simulation, it ends up as an analog signal to drive the speaker. When you stick a mike in front of the speaker, what the speaker delivers is what the mike will hear. So the quick answer is "no".
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This is the answer. Once it's analog, it's analog.

Frankly 16bit 44.1K is way more than it takes to reproduce a guitar signal. We can argue maybe about other instruments, but an electric guitar is lucky to have 70db S/N ratio, and doesn't pass anything higher than maybe 8K. An actual tube amp is even worse in both respects. A digital model can be quieter than the amp it emulates, but it still rolls off everything above 5K or so whether the speakers are sims or real.

But that ain't really the point. Once its coming out of the speakers, it's analog, like smooth, no stair steps. You don't have to worry about clock sync or any of the other things that can be a concern when transferring digital to digital.
 
A few observations if I may?

Guitar pups. There is no reason I can see why the harmonics should not extend well beyond 20kHz?

I have "specc'ed out" about a dozen models of amps, scores of times and they all had a significant output at 15kHz. Most were some 10dB or so down on 1kHz at 20kHz but I can pull some old spec tests and give more accurate figures.

The HF filtering comes at the speaker. "Proper" 12" guitar speakers typically have an on-axis response some 10dB or so down at 10kHz and falling rapidly (again, I can find some data) . Unfortunately the smaller, cheaper speakers, found in the smaller, cheaper modellers MIGHT have responses well past 10k. Even with good all valve amps I think most seasoned players will agree that the speaker is AT LEAST 50% of the sound? (tho of course, if you ask two guitarists which is the "best" speaker you will get 3 answers) .

Now, I am a well known digital dunce but AFAIK, digital amp modelling has been done by taking an existing amplifier's sound and making a digital model of it? (e.g. "this is our ***tface, Bender simulation"...."This is the one that looks like a sports jacket"...).

There has however been a range of amps on the market for some months now that eschews that process and instead models COMPONENTS. Cs, Rs and most importantly valves. The amps seem to have met with generally good reports.

I agree about "what you hear is what the mic picks up" especially a dynamic since most males past about 14 do not have the last 5kHz which a capacitor will capture.

Dave.
 
The problem you might be having micing the amp is the way you dial in the sound.

With a vst, you dial in the final sound you want and there it is.

With an amp, if you dial thr amp in so it sounds exactly the way you want it, then stick a mic in front of it, the mic changesthe sound. The mic has to be taken in to consideration when dialing in an amp for recording.
 
...or you dial in the sound you want and move or swap the mic til it sounds good! But I dint get the idea that the OP is actually hearing a problem. Seems more like he thinks there might be a problem based on a poor understanding of some dodgey theory. Plugging it in and trying it probably would have answered the question a lot quicker...

The STRINGS on the guitar probably do produce some fairly high frequency harmonics, mostly in the pick attack, but no magnetic pickup is going to pass them, and we wouldn't want to hear them if it did. There's a reason so few people play electrics with under-saddle piezos.
 
ashcat_lt said:
...or you dial in the sound you want and move or swap the mic til it sounds good!
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The thing is, the sound coming out of an amp does not sound like it does on a finished CD, no matter what you do. If you actually dial in the guitar sound of a finished CD coming out of the amp speaker, then stick a mic in front of it, you are screwed. This is why Crate amps sucked so bad. It's because that had the sound of guitar on a CD coming straight out of the speaker. It wouldn't mic up worth a damn for that reason. Think about it, if you played a CD and put a 57 in front of the stereo speaker, would the guitar tone be the same? No, of course not.

You eventually learn what a guitar needs to sound like, but most people don't start out that way. Especially now that what most people listen to is really over processed and there are amps that will actually sound like that. Back when I started, you got yourself a Marshall and that was that. No matter what you did with it, it wouldn't sound that much different. Most of the records I listened to had pretty unprocessed guitars on it. It was hard to screw that up. Now, it's pretty easy to get a rig that just sucks out loud.
 
SweetDan said:
I am assuming that since it's a modeling amp, the sound it produces is based on digital manipulation of the signal (i.e., not analog reproduction of the signal), or maybe even samples. I'm also assuming that the computer in the modeling portion of the amp puts out the modified signal (or samples) at some rate and bit depth (probably 44.1khz @ 16bits).

So, if I record the sound at a higher sample rate and depth (e.g., 96khz @ 24 bits), will my recording have "choppiness" or holes in it?
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I forgot to address this in one of my earlier posts. There is no 'choppiness, holes or stair-stepping in digital audio...None. It doesn't exist in the audio that comes out of the speakers.

The reason sims don't sound as good as real amps (which really depends on the sim and the amp you are comparing) is because the simulation is imperfect. It has nothing to do with any inherent problem with digital audio. Sansamp, for example, is an amp sim that is completely analog. It doesn't sound or behave exactly like a real amp either....because it isn't one.
 
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