Gxjcm800pre crashing


I just recieved my mod duo and I’m blown away by how awesome it is. The sound of the gxjcm800pre is fantastic but if I try to load two instances of it cpu goes to 100% and the mod crashes. Is it possible to get the same sound out of gxamplifier? I’ve tried using the jcm800 tonestack in gxamplifier but it sounds different to me.

Any advice would be great.


Before anything else, please update the plugins in the plugin store.
There’s likely to be quite a few plugin updates since the Duo was shipped to you.

(tip: remove all plugins from the pedalboard before updating all the plugins)

Yep, mod duo is updated and so are all plugins. If I add two instances of gxjcm800pre and two instances of gxcabinet the mod duo reaches 100% cpu.

update: If I instead add one instance of gxjcm800pre and one instance of gxjcm800pre st then it doesn’t happen.

cpu usage is still quite high compared to gxamplifier


The GxJCM800Pre plugin uses quite a lot of resources indeed, it is quite a heavy amp simulation to run, which is why it sounds so good.

Are you sure that adding the stereo version does not cause the problems? If the CPU usage monitor is blinking it is also overloading. The reason it is not showing 100% and is instead blinking is quite complicated, but it can be summarized to a bug in JACK (one of the services running on the MOD Duo).

What did you want to achieve with the two JCM800s? Perhaps I can assist you with an alternative solution.



Ah thank you, that is good to know. It sometimes blinks and sometimes does not… anyway it is definitely an unstable setup.

My goal is a double tracked guitar sound live. I used to do it with hardware; A guitar with dual outputs (neck and bridge pickups) running into two amp rigs.

On the duo I was going to split the mono guitar signal, send one through the fractal doubler 100% wet, the other 100% dry and run each to separate amp simulators.

It sounds ok using the gxamplifier but jcm800pre is very nice :smiley:

After some more playing around I realize I was being very optimistic! Just once instance of gxjcm800pre with a big muff already maxes out the cpu. Oh well, I guess that amp sim will have to stay out of my pedal boards for now.

One of my gripes about the DUO is that simulators take up a lot of CPU. I play the NS/Stick which has a bass side and melody side and I process each side separately. I’ve had to get pretty creative with how I come up with my sounds by using different effects and blending them together. In your case you may want to try just the cabinet simulators, they sound pretty great on their own after some effects. It’s a whole new way of thinking because you are unleashed from the thought that you need the traditional preamp… or even need a cabinet. You can take a cabinet plugin and go into a preamp… :fearful:

That just gave me an idea…
I have been struggling to get a good reverb sound. I’m looking for a smooth hall or chamber sound. Maybe putting it through a cabinet will smooth it out. Hmmm… :thinking:

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Thanks for your suggestions. I’m not sure I follow you though. You mean mod duo input > effects > cabinet plugin(s) > mod duo outputs > physical preamps?

I’ll take a look at the pedalboards you posted.


I really have no real suggestion…
For me… I find that I can do things that are physically impossible and I have come up with some solutions from thinking outside the box…

Try having the reverb in a side chain and using a low and high pass filter before it to limit the signal going to it. Most times, you’ll get a more natural reverb sound if you pre-process the signal, rather than post… though not always, so experiment :slight_smile:

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Thanks for the suggestion. I’ve been putting a low pass after… didn’t think to try it before the reverb. :+1:

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