neil's webbly world
Academic Pages
learn Russian

Voltage Controlled Mute Daughter Module

After much development the 3-channel voltage-controlled mute module is now ready for release. Ideally suited to the 3-channel mixer, it provides three channels of audio mute, each of which is controlled (muted) either by an external control voltage (CV), or by a front panel switch.

Of note is that this design supports both momentary push buttons and toggle switches as build options -- you can even mix them to suit your installation.


For interested parties the following documentation is provided.
Please note that all these documents are Copyright © 2011 Neil Johnson.

Switch Configuration

This module can be operated by either momentary changeover push button switches or with SPDT toggle switches, configurable per channel. The following table describes the build options and switch connections for both types of switch for each channel:

Note: a momentary push switch has three terminals: Normally-Closed (NC), Normally-Open (NO) and Common (COM). A toggle switch has terminals for "ON" (un-muted), "MUTE" and Common (COM).

ChannelResistorMomentaryToggleSwitch PadMomentaryToggle


I have identified a small number of issues with version 1 of the PCB. These are listed below.

  • Change R5, R17 and R36 to 1k0 (corrected in the parts list)

  • Replace R20, R29 and R33 with wire links (corrected in the parts list).

  • The top end of R2, R15 and R34 should go to V+ NOT Vref. To make this change solder the relevant end of these resistors to pin 8 of the nearest 7555. These mods are shown in the PCB overlay.

  • If you are using the expansion input on the mixer then you will need to add a strap between pins 9 and 10 of CN1.

Completed Module

Photo of the test board during testing. This is quite a dense board so best tackled by experienced constructors.

The first photo shows the VC mute mounted on the VC mixer board, showing the two boards together. The second photo is a close-up of the VC mute board by itself. As you can see it is quite densely packed for a through-hole board.


The PCB is no longer available for sale.

Copyright © 2001-2019 Neil Johnson