Frequently Asked Questions

What does “VCV” stand for?

There is no official meaning of the name “VCV”, but some users have suggested “Virtual Control Voltage” or “Voltage Controlled Virtualization”. These are good guesses, but “VCV” was chosen simply because it is easy to remember and type.

VCV Rack is the full name of our flagship software product.

Where is the “Rack user folder”?

The Rack user folder stores data readable/writable by Rack. You can open it by choosing Help > Open user folder in the Rack menu bar, or by navigating to

  • MacOS: ~/Library/Application Support/Rack2/
  • Windows: C:\Users\<username>\AppData\Local\Rack2\
  • Linux: ~/.local/share/Rack2/

When running Rack in development mode, it is your current working directory instead.

Does VCV Rack work with touch screens?

Yes, disable “View > Lock cursor while dragging params” in Rack’s menu and optionally set the “Knob mode” to rotary if you prefer.

VCV Rack does not currently support multi-touch gestures.

What is a VCV Rack plugin?

A plugin is a single software unit typically developed by one company or individual that can contain multiple VCV Rack modules. Plugins are loaded from <Rack user folder>/plugins-<OS>-<CPU>/.

How do I improve performance of VCV Rack?

VCV Rack simulates a modular synthesizer where each module itself can be a challenge to simulate on a modern computer, whether it’s a virtual analog model with hundreds of analog components to simulate, or a digital module designed to be run on an ARM microprocessor similar to your smart phone’s. A common patch of a hundred modules can require billions of floating point calculations per second to simulate and millions of 2D path elements to draw using OpenGL. Therefore, sometimes the following undesirable symptoms can occur when using Rack.

  • audio hiccups: Sparse and random millisecond-long audio delays. Caused by sporadically missing the audio block deadline, due to thread switching due to high CPU of other threads/processes/applications, disk activity, uncommon high-CPU branches in the DSP code, etc. during audio block processing. Depending on the audio driver and device, either zeros or the last generated sample value is inserted until the audio block is ready.
  • audio stuttering: Consistent audio delays every audio buffer block. Caused by the minimum CPU time required to process an audio block being greater than the real-time duration of the audio block.
  • high power usage: Causes laptops to drain their battery faster than during idle or typical use. More power is used by CPUs and GPUs when they are idling less often (on the microsecond scale) and operating at higher clock frequencies (managed by the OS or BIOS based on average resource load).
  • high CPU/GPU/case temperature: Causes the fan regulator to increase fan speeds. Heat is directly proportional to power usage.

If any of these symptoms occur, you can attempt to treat them using the following tips. Note that some tips have trade-offs or might not provide any benefit for your situation.

  • Rack DSP:

    • Use Rack’s CPU meter to identify high-CPU modules that you could remove or replace.
    • Turn off the CPU meter when you don’t need it. Measuring the CPU time of each module in your patch consumes significant CPU.
    • Increase VCV Audio’s block size to the highest tolerable number. This results in proportionally higher audio latency but proportionally decreases block processing overhead and allows higher jitter in sample processing CPU times.
    • Use the lowest tolerable Engine sample rate. Engine CPU usage is almost exactly proportional to its sample rate.
    • Disable modules in your patch that you aren’t currently using by right-clicking on their panels and choosing Bypass.
  • Rack multi-threading:

    • To maximize the number of modules in your patch without audio stuttering, increase the number of Rack engine threads until no stuttering occurs. See Threads.
    • To reduce power usage and temperature, use the smallest number of Rack engine threads that does not cause audio stuttering.
  • Graphics:

    • Decrease Rack’s frame rate to the smallest tolerable value. See Frame rate.
    • Use a dedicated (discrete) graphics card, such as Nvidia or AMD. Rack is not designed for integrated graphics such as Intel HD/Iris. See System Requirements.
    • Make sure your graphics drivers are up-to-date.
    • If using an Apple Retina display on your Mac, set the Rack app to use Low Resolution Mode.
    • Use Rack in fullscreen mode so the graphics card does not need to render the OS user interface and other applications.
  • Audio hardware:

    • Use a dedicated audio interface rather than your motherboard’s audio hardware. This slightly decreases the CPU overhead of sending/receiving audio buffers.
    • Avoid using the DirectSound driver on Windows. Instead use ASIO or WASAPI. If you do not have an audio interface with an ASIO or WASAPI, install the freeware software ASIO4ALL. This installs an ASIO driver that communicates directly with WDM audio interface drivers, bypassing MME and DirectSound.
  • Operating system configuration:

    • Avoid running unnecessary programs while Rack is running.
    • Configure your CPU to run in maximum performance mode (not energy-saving mode). On Windows, see How to enable the High performance power plan by Ableton. Mac automatically adjusts your CPU performance when applications require high CPU.
    • If you are able, plug in your laptop. Operating systems reduce CPU performance and power consumption while running on battery.
  • Audio/video recording:

    • Use VCV Recorder to record audio or video. Unlike non-Rack-specific screen recording software, it operates in Rack engine “time”, not real-time, and therefore does not record real-time audio hiccups/stuttering. This means that any hiccups/stuttering you hear in real-time will not be present when the recording is played back.
  • Computer hardware:

    • Although Rack’s System Requirements suggest that computers as old as 2013 can run Rack, it is recommended to use a computer from 2016 or later that is designed for gaming. There are many gaming laptop and desktop computers on the market for as low as $300, the price of an average hardware Eurorack module. Unfortunately, Apple’s MacBook Air and older MacBook Pro models are not designed for gaming (despite their high price!) and are therefore not recommended for VCV Rack.