How to use CV-enabled hardware with Live
What is CV?
CV is an abbreviation of "Control Voltage"; An analog method of controlling synthesizers, drum machines, and other similar equipment. In the context of this guide, however, we will specifically refer to devices made in the Eurorack format.
This guide requires at least an intermediate knowledge of modular synthesizers. If you are completely new to the world of modular synths, however, this video from Benn Jordan is a wonderful resource to get you started.
It is also strongly recommended that even advanced users first refer to our CV Tools: Overview & Technical FAQ. Although the CV Tools pack is not a requirement for using CV with Live, the article contains crucial safety information and provides the necessary context for the rest of this guide.
- Step 1 - Requirements
- Step 2 - Configure Live's Audio Preferences
- Step 3a - Routing and recording (using a MIDI to CV converter)
- Step 3b - Routing and recording (using a DC-coupled audio interface)
- Step 4 - Potential issues when using CV with Live
To integrate synths, drum machines, or hardware samplers into Live, see Using external hardware (with MIDI).
If you are using external effects, see Using external audio effects.
Most audio interfaces can connect modular systems with Ableton Live in some capacity, even if only to record the audio output. However, since Control Voltage is only compatible with DC-coupled inputs and outputs, interfaces tend to fall into one of the following three categories.
Configuration 1: Audio Interface with DC-coupled inputs & outputs
These devices reliably send and receive CV.
Configuration 2: Audio Interface with DC-coupled outputs and AC-coupled inputs
These devices reliably send CV, but cannot receive it.
Configuration 3: Audio interface with AC-coupled inputs & outputs
These devices cannot reliably send or receive CV.
Triggers & Gates: An Exception to the Rule... for those who are careful!
Triggers & Gates are used within a modular system to signify binary events, similar to MIDI "Note On / Note Off" messages. Since these events do not rely on strict DC values, users can sometimes send these signals to and from their DAW without using a DC-coupled interface. However, like any other modular signal, please remember that these can go all the way up to 10 volts! Be sure to attenuate it down to line level (about 1v max) before connecting it to your interface to avoid damaging any hardware.
DC-coupled interfaces are simply normal audio interfaces with different types of input and output jacks. For specific instructions on how to set one up, please refer to our article on Setting up an Audio Interface.
However, it is often desirable to use multiple interfaces simultaneously. For example, you may want one interface to send CV to a modular system and another interface to send audio from Live's Master channel to a set of studio monitors. This can be challenging since Live's Audio Preferences only accesses one audio device at a time. To work around this, you may need to create an Aggregate Device, which combines multiple interfaces into a single virtual device that the user can access simultaneously.
Note: One unfortunate quirk of this method is that Live may not be able to consistently recall custom I/O names saved into Preferences.
When using an external MIDI to CV converter, the instructions from our article on Using external hardware (with MIDI) will still apply.
However, one important stipulation is that users are currently unable to Freeze and Flatten tracks that contain Max for Live devices that utilize external audio routing (such as those found in our CV Tools pack). To work around this limitation, use a pair of MIDI and Audio tracks to record the incoming signal.
When using a DC-coupled interface, CV signals are indistinguishable from audio signals. As a result, the instructions from our article on Using external audio effects will still apply. However, take extra care not to send any CV directly to your studio monitors to avoid damaging the speakers.
- Even the best modular systems tend to carry some amount of DC offset into the resulting audio. To mitigate the effects of this, it helps to place an instance of Live’s Utility device with the “DC filter” switch enabled somewhere in the signal path.
DC-coupled interfaces tend to have a rather high noise floor, which is why most manufacturers opt for AC coupling. Unfortunately, this also means that they often have difficulty maintaining the accuracy of precise voltages (such as 1v/oct signals). That being said, less precise signals (such as LFOs and Envelopes) can often be recorded and played back with very little noticeable difference.
As with most things modular, it is sometimes easy to get lost in a patch! However, one of the benefits of digital integration is the advanced metering options available to users. If unsure how something works, you may want to use a digital oscilloscope to check on various signals in your path. (This one works rather well, in our experience).
Since CV essentially works as an audio signal within Live, many of the same recording and signal routing techniques in traditional audio workflows apply. However, one should always take extra precautions to ensure the results sound consistent upon playback. For instance, a modulation signal may sound fundamentally different when placed into Sampler, where the default setting (a) reduces the amplitude by 12 dB, (b) applies a low-pass filter, and (c) enables velocity control. This is usually desirable for audio but will not work well for precise modulation.