adding Audio-8 to rack slows VCV Rack down

so I have an clock module running VCV at 140 bmp. I add an Audio-8 to the rack to get audio into my sound card, and VCV Rack slows to half speed.

am I missing a step in set up?

MOTU 828es, OSX


48kHz on both MOTU and VCV Audio-8

what happens when you first add the audio-8 and then the clock module?

it actually doesnt need the clock…I thought adding the clock might force it to stay on time. but no matter what I’m using VCV slows when I add an Audio-8. I’ve even tried start VCV first adding the Audio module, then starting Logic [using it and the MOTU to record] and time in VCV gets cut in half



could you define what is the mean of “slow” (since you said you don’t need the clock, ) what modules do you have in the patch?

if you notice it slow down when the audio module is added , how you know it is going a normal speed have not the audio 8? do you you already have a audio module in your patch?

the vcv rack could not work with two audio modules, instead of two audio 8 use one audio 16

I’ve got 2 Marbles, CV-CC, bass drum module, hihat module. Using one of the Marbles for clock. That’s all there is in this rack.

I know it’s at the proper rate and slows cuz I’m sending CV to my ER-301. I was just adding the Audio modules to get a quick BD and HH from VCV

I add Audio-8, no problem. I choose what it will output to, and VCV drops. The whole thing slows.

This is a known bug feature behaviour of Rack. You need an Audio module for the engine to run at the right speed, otherwise it runs too fast. (So it’s more like “Not having an Audio module in the rack makes it run too fast” than “adding Audio-8 to rack slows VCV Rack down.”)


You always need to add the audio core module first (select the proper audio driver), and then build your patch.

Even if you don’t need audio output.


I have never thought about this…what can I do with vcv rack without an audio module?

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you could just send midi/CV out of VCV and control other hardware synth / Eurorack …

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Control anything that receives CV-midi: art installations, light/video installations, mechanical experiments.

Without an audio core module, that is if tempo sync is not a requirement.

But reading again now through the OP’s posts it seems more like OP was trying to add a 2nd audio module.


If you are using multiple audio modules in Rack 1 @phaelam, that’s not supported.

From the Rack manual

“Note: Using multiple Audio modules is experimental and may crash Rack or render unstable audio.”

ya…no…im not using more than one. BUT, I was using it without one.

thanks @Richie and @Eurikon for pointing out that it actually needs one in the rack to function correctly. :+1:t6:


things of course I have made in the past…but have never thought to work without an audio module!