With the release of firmware version 22.214.171.124 the mono switch feature is now available for V25 preamps. Please see the clarifications and qualifications listed below. This firmware version will be uploaded and made available for download from our website later today (7.17.17).
1) Mono mode is toggled on/off by pressing the Enter button on the remote 2 times in a row within one second. A single press does nothing.
2) You need firmware version 1011 or later to enable this feature. You can tell which version firmware your V25 has by observing the 4 digit number displayed a few seconds after plugging in its power supply.
3) Mono Switch only works if your V25 board is equipped with an LDR in the mono switch position on the V25 board. If you update your V25 with version 1011 or later firmware and Mono Switch doesn't toggle between stereo and mono then you don't have a Mono LDR in your preamp. It's a simple matter to buy one and plug it in.
4) Unfortunately, the Mono Switch feature does not work with V25's pairs wired up in the default balanced audio arrangement. Let me elaborate on that. There's a design trade off with V25s used in balanced pairs. You can either have the channel balanced adjustment feature or mono switch feature but not both. If mono switch is more important to you you can change the signal wire hookup to the V25 boards to make Mono Switch work but after that channel balance adjustment will be wonky. I don't have documentation on this posted online yet so if this is something you want to do please contact me.
5) All V25 preamps shipped from July 17th going forward will have this feature enable in the firmware. Folks ordering the DIY V25 board will have to specify adding the Mono LDR if you want to use this feature.