Audio clipping on output in Modep

Patchbox OS MODEP
1

Hi,

I’m testing out MODEP using PiSound and a Raspberry Pi 3B - it seems to work great at a certain level, but I get an awful lot of clipping.

I’m trying a simple setup with a reverb unit (like Roomy) into GXAmplifier-X, then straight to the output. The input is my guitar, the clipping light on the PiSound never lights up (I’ve got the gain down to a sensible level). It’s also not clipping on the way out to my mixer - I’m generally always at about -6dB or more. The problem seems to be when I use a lot of attack playing the guitar, I get some great distortion sounds out of GXAmplifier-X, but at a certain level I get digital clipping on top.

Changing to a clean-sounding amplifier setting, I can still get the clipping if I strum full chords, especially using the lower-octave strings. It’s like I’m running out of headroom?

I figure the clipping is happening in the digital domain within MODEP itself, so I thought maybe if I put a limiter at the end of the signal chain, I can stop it from happening… but, bizarrely, any limiter I use just clips like crazy as soon as I hit the threshold level! Turning the threshold level down makes the clipping worse, turning it up all the way generally gets it back under control.

I’ve found by turning the output level down on the GXAmplfier-X seems to help, and I can virtually eliminate it, but I still occasionally hear some clipping and I have to get the output down pretty quietly. It’s also find by switching guitar to something with more gain, of course the clipping can come back, and I therefore need to set up my volume levels really carefully on a per-guitar basis, which means setup time on a guitar-by-guitar, patch-by-patch basis. I’d just love to be able to plug-and-play with this thing but I can’t.

Is there something I can do in MODEP to prevent clipping? Or would something like a DI box help?

Thanks,

Chris.

2

Does the clipping happen without any pedals on the board, when input is connected directly to output?

3

Thanks for the reply!

It doesn’t clip if I run the clean signal through without any pedals - I’m starting to wonder if it’s primarily the amp modeler. But the two things that cause clipping are GXAmplifier-X (unless I turn it down so low it doesn’t really want to break up using the modeled distortion), and the limiters.

The fact the limiters are clipping so badly makes me think it’s something wrong with my setup.

My primary aim for this is to try to model different amplifiers via the piSound, taking a clean guitar signal in to begin with, but I’d also like to try using my hardware guitar pedals, and I just know as soon as I start that I’m going to get more clipping.

4

Hmm, if the signal is fine when the input is connected directly to output, that means the issue is in the software processing of the signal. You should try to play around with the parameters to find whether there are some combinations that work.

Or some plugins might just be doing something wrong, try looking for alternatives.

5

Thanks - having experimented more, to me it seems like the GXAmplifier-X and the limiters I’ve tried (sorry, forgotten the names of them!) just seem to clip badly.

The GXAmplifier-X is working fine 90% of the time, but if I push the gain too hard or use a lot of attack while playing the guitar, it’s going to clip. The trouble is that I’ve tried other amp modelers in MODEP, and none of them seem to work very well. The AmpVTS CAPS looks promising, but I get zero output from it when I put it in the signal chain - I guess this doesn’t work either?

Anyway, I’ll keep playing around with this, hopefully I can find some sort of setup that does work.

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