about ASIO4ALL

Normally you need ASIO4ALL but is there anything like that for linux mint that really works with REW

ASIO4ALL is a bridge between ASIO API and standard windows audio interface. It allows multichannel transfer and bypassing windows mixer for audio devices without ASIO drivers provided by their manufacturer.

Since ASIO was not designed for simultaneous input and output to different audio devices with independently running clocks (the ASIO transfer call bufferSwitch passes input and output data of same length in one call), ASIO4All cannot work correctly in such configuration. For windows the way for REW is using its Wasapi exclusive driver instead which separates the input and output streams and runs them independently (java device names starting with EXCL: ). Wasapi exclusive was released with Windows Vista in 2007, ten years after ASIO in 1997.

In linux the audio subsystem alsa from designed for simultaneous acces to any number of soundcards in any direction. There is no third-party API like ASIO needed. REW can output directly to hw alsa devices (called cards, listed by command aplay -l) using native java interface, or to PCM alsa devices (listed by command aplay -L) using a custom java interface for PCM devices distributed with REW (java names starting with PCM: ).

Most linux distributions come with a sound server (Pulseaudio or recently Pipewire) which commonly reserves all alsa audio devices for its use. Therefore prior to using a raw alsa device it's important to disable such alsa device in that sound server - e.g. https://askubuntu.com/questions/666...rtain-device-from-being-grabbed-by-pulseaudio , https://unix.stackexchange.com/questions/620961/disable-remove-audio-source-pulseaudio , or with udev https://lukas.zapletalovi.com/posts/2020/force-pulseaudio-to-ignore-a-card/ https://jamielinux.com/blog/tell-pulseaudio-to-ignore-a-usb-device-using-udev/

Or using pavucontrol or the built-in audio GUI for the given distribution. In Mint Mate (the system I use) it's like this (Vypnuto means "Off")

I have a UMC22 with a measurement microphone but when I try to run REW it just goes round and it says to low signal. I have tried connecting out to L and in to R and vice versa. It has worked perfectly fine in Windows 10 but I can't get it to work in Linux, what am I doing wrong? I thought it might have something to do with ASIO4ALL, that it is not available in Linux.

Did you disable your UMC22 card in pulseaudio?

Did you chose the UMC22 card in java driver of REW?

Did you check the card controls (volume, muting, etc.) with alsamixer -c CARD_ID?