3-Channel Mono Mute 1-Channel Stereo Mute Click-Less Muting based on Vactrols STRIKE Buttons for Performance Mutes LED Indication MUTE or GATE Mode for Channels 1-3 Wrong polarity protection 3U Eurorack module, 6 HP wide Power consumption: 25 mA at +12 V and 14 mA at -12V

The module consists of three boards:

Front PCB Panel Main PCB Vactrol Board
ONCE IN A WHILE6HP 3-Channel Mono, 1-Channel Stereo CV Click-Less Mute ONCE IN A WHILE is a 3-channel mono and 1-channel stereo mute switch with CV control. Any audio or CV signal fed into the IN jacks and taken from the OUT jacks can be muted and unmuted with a latching MUTE button per channel. If a channel is not muted, you can also mute it momentarily with the dedicated STRIKE button. Conversely, you can unmute a mono channel with the same STRIKE button if it is muted (this is not possible with the stereo channel). LEDs indicate whether a signal is being passed. You can also use CV signals to mute channels. Just connect a gate, LFO or envelope to the CV inputs and the channel will be muted from a voltage of about 2 volts. Even if you apply a control voltage to the CV inputs, you can mute the signal with the MUTE (latching) or STRIKE (momentary) buttons.   Before soldering the module, you can decide if you want to use one of the mono channels alternatively as a low-pass gate. It's a single resistor you need to change and a mono channel becomes an LPG when a CV signal is patched into its CV input. So if the channel is muted, it will be unmuted again when the CV input is high. Mute mode = CV mutes the signal when it is not muted. LPG mode = CV unmutes the signal when it is muted.  The first input is normalized to the other inputs. Therefore, you can also use ONCE IN A WHILE as a 1 to 4 buffered multiple with individual mute switches. ONCE IN A WHILE was designed to provide click-free muting for audio signals, but has become much more performance-oriented with the addition of momentary STRIKE buttons and CV inputs. It was optimized to be used with the VTL5C9 Vactrol. You can also use other vactrols, but then you may get clicks when muting audio.