its because you're using a solid state amp DI into an inteface, i had the same problem about 3 years when i was tracking some guitar parts for a singer. The only real solution is to mic the amp, and avoid going DI. Marshall MG series, and AVT series will always have this problem unless you're playin something with a lot of distortion and any interferences with the signal path would blend in and be unnoticable. Try recording a scratch track with a lot of distortion and see if you're still getting the noticable "digital" distortion at all.
If you were using a true tube amp i'd say get an attenuator and play around with it some more, but your best bet with that amp is to put the cab in an isolated room, or vocal booth and just mic it up into the interface.

or just get a tube head. Im kidding, partially, but one thing i've learned is that there is always a shortcut around spending a bunch of money to get a good sound, atleast in a guitar-equipment-prespective.

Does the waveform have visible clipping?

It read like your clipping the output from the amp if everything else is set properly.

There is actually no reason to use your guitar amplifier if you want to go DI into your box. Especially if all you want is a clean guitar sound. I'd say use a microphone on your amp, if you want to use your amp. If you want to use your amp DI output, make sure you're going into a line input, not a DI input. The DI input should only be used when you take the output from your guitar directly into your box. That is, unless, you are using some kind of effects built into your amplifier? Then you might want its direct output.

Thinking inside the box
Ms. Remy Ann David

I agree... Go straight into the instrument input on your firebox, and apply some light saturation in software if you want an amp sound. The output on your amp isn't speaker emulated, so its like plugging into a stomp box. The speaker of your amp smooths it out and limits the EQ range, adds compression, and lots of other things. If you really want to re-create that, you have to mic it.

If you have software like guitar rig or waves GTR, you can just go DI and choose your sound in software.

What did you mean add saturation in DAW? I use an amp simulator, is that now what you were talking about?

If you are using an amp simulator (or any other plugins) in your DAW, there are more links in your signal chain. You could easily be driving the output signal to clipping with them.

If it was clipping the output signal then I would be able to see it with the level meter though right?

Guitarfreak wrote: If it was clipping the output signal then I would be able to see it with the level meter though right?

That's correct. But it could also be clipping in one of your plugins. Each plugin is part of the gain structure. You can get clipping at any gain stage.

I'm almost positive it is the amp though, I use an amp sim but only after tracking, and in this particular case the clean track came over distorted with no plugs. I can DI just fine straight from the guitar, and it comes out fine, so it's definitely the amp then. I don't understand the physics behind it but...it is what it is.

Just for clarification you are using the Emulated Direct out on the rear of the amp cabled to your firebox?
Are you going in through the ports on the face of the unit? That is the preamp cicuit and it is possible that the signal from the amp is too hot for the preamp which could cause the clipping even though your gain out from the preamp after clipping is not high enuf to clip in the daw.
Try putting the Direct Out from the Marshall into the line in on the rear and see if that works. Let us know. You might have to assign the track in your software to "see" the line in.

Your assumption was correct, however I already thought of that before I posted and tried to plug it in the back. It was the same deal, where it clipped at the top 15-20% of the signal. This was also the case where it made the clipping sound at whatever preamp setting I had it on, i.e. it made the same kind of distortion sound at 5dB as it did +25dB so I figured it was unrelated.

Thanks for the help guys!

My thinking is that there is something wrong with the emulation circuit of the AVT itself.

jg49 wrote: My thinking is that there is something wrong with the emulation circuit of the AVT itself.

Could be, I had it sent in a while ago to Marshall under warrantee and they sent it back saying there wasn't anything wrong with it. But I've noticed that there really isn't much depth to the distortion sound, like it sounds airy and not tight and warm. But whatev.