What are your jack settings to get VCV Rack running fine in Linux

Hello everybody,

I would be pleased to share experiences about jack and VCV on Linux. I’m on ubuntu studio 21.10 and was experimenting many xruns. I run a old MOTU 828 MKII device with FFADO drivers (developed by crazy devs who did an incredible reverse engineering job to have it work nicely). Very surprisingly the solution was the opposite of what I thought were the good settings for jack. I first tried to increase the buffer size (up to 1024) but I still had xruns. And the solution, at least for me, was to decrease the buffers size down to 128, with 2 jack periods.

Did you observe the same thing on your side ?

check this

jack should have real time access (also in the same link)

Of course, ubuntu studio comes with low latencies kernels, I’m currently on 5.13.0-22-lowlatency. Ubuntu Studio comes “factory” with rt access. And the KXStudio repos are not really maintained (many obsoletes stuffs). I was just asking for other linux users about their best settings for jack for VCV, as I’ve been testing a lot of them (btw ubuntu studio comes with a very handy app named studio control, an equivalent to qjackctl that also bridges pulseaudio with jack which is realy complicated and hazardous to do with qjackctl). I was just surprised that I had to go towards very small buffer size and jack period to have a clean run of vcv, just wanted to know if other linux users experimented the same thing because VCV can create lots of xruns (even with RT access and lowlatency kernels). And this guide doesn’t really take in consideration the specificity of FW sound devices, FFADO firewire is prefered to alsa firewire to have low latency.

I use whatever settings my soundcard requires.

Which for me is:

What is your sound card ? Do you experiment xruns ? I’ve never seen this soft mode and Force 16 bits in jack settings. Do you use Jack ?

This is jack, configured via Cadence. I have an M-Audio Fast Track Ultra and I’ve never experienced xruns with Rack (v1 or v2).

But again, these are specific settings for my card. It doesn’t make a lot of sense to compare different settings for different soundcards.

Do you have a specific patch that you see problems with?