Pre-processing before Amp sims

I'm pretty new to the world of Guitars and Amp, I've never played through a real amp, so just have TH2 (3 sort of) and MarkBass. These come with stomps of compressors. What would be the benefit of using these before and amp over those in the DAW; CA2A, PC76 and Boz+10 for example. I'm guessing having a modelled high end compressor over a modeled stomp box.
 
I've also been investigating pick ups and note comments like 'more attack, more sustain, deeper sound, more even dynamics, more presence etc. These all seem the subtle qualities you can achieve processing the sound pre Amp Sim, to mimic a better sounding an instrument. Of course a better sounding instrument would be better, but I've wondered about using transient designers, Channel eq's etc before the amp sim to achieve these qualities

Do you ever use the compressors stomp boxes that come with Amp sims?
 
Anything I'd try wouldn't be applied to the audio file, so it would easily be removed.
 

Not so much for me, as I prefer clean. And end up trying to find out what in the stocks are causing the signal to break up. My thinking would be more to presenting a more level playing to the amp, to make up for my playing inconsistencies.  
This is for bass as well as guitar.
 

Can you clarify the signal breaking up? You mean the signal dropping out? A compressor can help some with this, but the signal will just "cut off" at a certain point. Same with using a noise gate. A feedback loop of some sort (guitar receiving the notes back from a speaker) will help sustain but can be tricky and potentially annoy others. Another option is to raise the height of pickups to be closer to the strings (fret at the highest fret and adjust the pickup height so that it almost touches). The bridge pickup is good to do this with (since it also catches more harmonics), but the neck pickup is usually best left down a little below that (depending on the output).

Regarding pickups, I don't think you'll find stomp boxes that'll do what various pickups will do. The pickup magnetics interact with the strings and ways that are dependent on how you strike the strings. The non-linearities in the magnetic core of the pickups also modify the tone in ways that are dependent on how you strike the strings. The position of the pickups relative to the end points of the string and position of the right hand also changes how the sound transforms over time. These are all examples of dynamics being in the hands and why people have so many guitars (they have different pickups and react differently to how you play). Stomp boxes have no information about how to strike the strings. They can't react the way pickups do.

In my experience and opinion, software models of hardware of compressors all sound about the same. The differences are subtle at best and the color or character they supposedly impart on the signal are also subtle at best unless and until you get into extreme settings (i.e. the 1176 all button mode etc).
 
Here's a thought experiment to show what I mean. Take an individual source track and clone it several times. Then use an 1176 on one track an LA2A on the next and Sonitus on the next and a Focusrite on the next etc. Next set all tracks to roughly the same (not extreme) amount of compression and same output level. If you did all that, I would bet that 99.999999% of the DAW users out there could not do any better than random chance at guessing which was which in a blind listening test.
 
I've said this before. The reason I choose one compressor plugin over another has nothing to do with sound. It has to do with the controls on that particular model and my understanding of how to use them. I gravitate toward the 1176 because I know how to get what I want out of it. I could get the same results with lots of other compressors, but it would take me longer because I don't know their controls as well. Also to be fair, I gravitate toward both the 1176 and the LA2A because they're in the prochannel which makes them quicker and easier to use and adjust.

So the bottom line is use which ever compressor you want because at the end of the day, compression is compression and it all sounds more or less the same regardless of which model you use. 

That being said, when I'm doing guitar usually go with the stomp box models rather than inserting a 'high end' model before the amp. I have a couple of reasons for that. First off, when I'm using compression on a guitar signal chain going into an amp, I'm usually trying to different things with the compressor than I when I'm using compression in a mix down setting.
 
Mixdown compression is often about taming dynamic range (keep the peaks under control) and sometimes also a bit of fattening. With guitar, its usually more about fattening and sustain than about keeping peaks under control. And like I said above, for me choosing which to use is about knowing how to get what I'm looking for from the control on that particular unit. When it comes to guitar compression, its faster and easier for me to use the stomp box models because I know how to set them. I could use an 1176, but chances are no one will hear the difference when its all said and done so why bother?

realize that the better sims, use the natural signal from a guitar's pickups, as the 'starting point' to define the dynamics and touch sensitivity of what happens once it gets into the sim.
 
if you mess with the signal coming in, the sim will probably not react the way it was intended.
 
look into the REAMP system.
 

yep.
those machines want to control the input,
not have it driven thru some other option before hitting their controls.
 

Thanks for the input guys.
 
Regards the gain structure, I'm still learning this, being I like clean tones, TH2 meter stays in the yellow, and I just make sure I don't clip at the input. Coming from physical synthesizers and drum machines, I'm inclined to get the best signal out of my guitar for noise floor reasons, and deal with gain inside sonar, than
 
I investigated PUP heights too, and adjusted the neck height. top and bottom strings were the same hieight and I'm liking the bottom strings a little further away
 
I inclined to agree with TLW, I don't see what would be so special about stomp box compressor apart from it's portability and ease of use on a stage. Which isn't the scenario here. If I want a fast compressor before a sim, it seems I have some better tools in sonar for the job.
 
Being players often do put stomp boxes before an amp, I don't see why it would care if it's from an external VST, or a purpose built stomp that comes with the modeled amp.
 
The conditioning I was thinking about would be subtle changes, in the same way different PUPs create a dsubtle difference. I'm not trying to model a PUP. But if an UltraJazz PUP gives my bass say deeper bass, and stronger attack, I can bring these qualities with a transient designer and EQ. It's like the common question "EQ before or after the compressor". Seems the same scenario here to me. If there is a resonance going on with my Guitar, why not deal with this first?  I can see how a compressor before is going to affect how the amp responds, but evening out the a touch rather than squashing it was what I had in mind. So stong nots are more consistant in how the amp is affecting them, and softer notes are bought up.
 
I guess it's just not commonly done. I thought I would get some suggestions and handy tricks. Seeing at least Soundwise is experimenting with it, it doesn't feel so out there.  I'll play with it some more I guess.
 
I noted there were no comments about bass, thought there would be more players of both

Amp Sims have a tendency to be too "perfect" or hot at higher frequencies. A LPF between 4-7K before compression is another item that may help.

So much of tone is personal preference so is impossible to give you a slam dunk reply.

Another learning tool is to take settings to extremes one at a time so you can easily recognize what is really going on. Swap order of modules in chains, etc.

I'll certainly run compressor plugins on bass, whether recorded using an MXR bass preamp, Sansamp or using a software amp sim. Which seem to perform better than most of the guitar amp sims for me.

I've done it with guitars as well, often the BozDigital 10dB compressor which I find sounds pretty good with guitar.

The guitar compressor pedal I use is a Pigtronix Philosopher's Tone, mostly for playing glissando or after a Qtron envelope filter which pushes out some high gain peaks that need evening out a bit before they hit other pedals or the amp. I put a Keeley set pretty mildly in my bass setup to control filter peaks and resonance as well.

In Overloud's Markstudio, changing thie mics seems to to make small noticeable difference (I keep finding myself on the ribbon mic)

KamikazeI inclined to agree with TLW, I don't see what would be so special about stomp box compressor apart from it's portability and ease of use on a stage. Which isn't the scenario here. If I want a fast compressor before a sim, it seems I have some better tools in sonar for the job.
 
Being players often do put stomp boxes before an amp, I don't see why it would care if it's from an external VST, or a purpose built stomp that comes with the modeled amp.

I didn't say that you can't use a general purpose compressor before the sim.  My point is that if you are looking to emulate a classic tone that was achieved with a specific stomp box, you'll probably find it easier to get that tone using the stompbox emulation rather than a general purpose emulation.  If you are looking for something different then, by all means, you'd want to try a different compressor.  Again, there aren't any rules and there isn't any "better" other than what you think sounds better.  
 
The real world LA-2A, stompbox compressors, etc. are analog circuits that implement the theoretical concept of compression and as such have imperfect audio characteristics beyond their theoretical purpose.  The available controls differ and that is going to affect what compression characteristics you can dial in.  The detector circuit design is an obvious example of something that is going to differ drastically and affect the response (a big part of the allure of the LA-2A in the first place though that might not be the response you want for a specific guitar tone).  An emulation of a battery powered stompbox isn't going to have the 50hz/60hz noise that an accurate LA-2A emulation will have.  That's why emulations exist rather than everyone just using something like the Sonitus compressor for everything.  I'd suggest trying all three all over the place to understand the difference (a stompbox emu, a studio emu, and a "purer" compressor).  These concepts apply to any other effect -- not just compression. 
 
Of course, all of this depends on the accuracy of the emulations.  I wouldn't be surprised if some emulations are just purer compressors with controls slapped on to work like the "emulated" hardware.