Simulating a mod on my Linux PC


I’m having the same problem. I’ll try the mod-app


mod-ui by default assumes you want to do development, and for that it skips mod-host integration (which needs jack running).
set MOD_DEV_ENVIRONMENT=0 environment variable before running it to make it connect to mod-host.
this of course assumes you have mod-host running before.


Thanks! Now works fine!


Hi, I’m tring to do the same things, and I’m able to load Jackd, Mod-host and mod-ui… but I’ve a very newbie question… Where I’ve to put the .lv2 plugins?? 'cause I can’t see its on mod-ui, but I’ve compiled and put some .lv2 on /home/user/.lv2 folder…

Thanks in advance and sorry for this maybe stupid question!


LV2 has an official page documenting where we should put the plugins.

if you can’t see them, you did something else wrong…


Hi @maoz

the LV2-plugins live in $LV2_PATH. You can try to do the following as the user which runs “mod-ui/mod-host”:

echo $LV2_PATH # shows where your LV2-Plugins live

Or you can change this variable before starting mod-host/mod-ui pointing to the right folder:

export LV2PATH="/my/favorite/path"

Regards, Holger


Hi all,

just FYI:

On a Raspi3 (with pisound audio card) I have trouble using mod-host loaded into jackd. Loading with jack_load mod-host works. Also running mod-ui and creating a pedalboard. But when loading another pedalboard or erasing the current one, I often got a hanging jackd.

I tried a little bit around and looked at some information on stdout. The problem seems to happen when mod-host is calling jack_deactivate():

Output of
[I 170908 17:05:17 host:987] [host] popped from queue: feature_enable processing 0
[I 170908 17:05:17 host:1014] [host] sending -> feature_enable processing 0
[I 170908 17:05:17 host:987] [host] popped from queue: remove -1
[I 170908 17:05:17 host:1014] [host] sending -> remove -1
[I 170908 17:05:18 host:999] [host] received <- ‘resp -203\x00’
[I 170908 17:05:18 host:987] [host] popped from queue: feature_enable processing 1

-203 means:

… and is called at effects.c:3406:
if (jack_deactivate(effect->jack_client) != 0) return ERR_JACK_CLIENT_DEACTIVATION;

I don’t know if this may also happen on other architectures. My Mod-Duo works fine - I don’t know if it is using the mod-host embedded into jack. So this is not an error report - only a hint for others who may run into the same problems.

BTW: Loading mod-host as a normal process instead of jack-embedded works fine…

Regards, Holger


Hi everyone,

Any recomendations about the best Linux Dist to run MOD?


Works best for me on *buntu or *bian distros. I personally use Kubuntu.

Regards, Holger


Thx @Codeman!


I would recommend checking the version of Jack running on the distro. The one on Debian is very old and prevent making the most of your duo (such as inserting it inside your workstation jack network and recording from it with Ardour as described in other posts here. It works with Debian but performance really doesn’t make justice to the gear).