Here was how I solved the problem:
- Make sure only the channel in use is turned up - keep the others turned right down.
- Install the ASIO USB audio driver from this site (it says that it does not support the Alesis USB mixers, but I found that it did, although it took a couple of attempts to install). This driver is a demo version which puts a beep in audio every thirty seconds. It costs 59 euros for the full version - which I ultimately had to pay just to get the mixer working.*
- Select the correct USB driver (probably marked something like "USB Line in") in your recording software.
- Right click on the speaker icon in the taskbar. Select "Recording Devices" then select the "Recording" tab. Right click on the USB driver, select "properties" and turn the level down. You should keep the gain in the USB driver turned down as low as possible.Start at 50%.
To adjust the other levels do as follows:
- Set the gain control in the Audacity software to about two thirds up.
- Plug in the microphone and bring the "Gain" control on the Alesis mixer up until the light LED marked "clipping" starts flashing.
- Turn the "gain" control down just far enough to stop the flashing the flashing.
- Reduce the "level" control till the levels are correct in Audacity or your other recording software.
This should give you a nice clean and hiss free recording. This worked for me and I hope it will work for you too.
*This being due to the way Microsoft changed their USB audio driver to one optimised for use with communication headsets which has a high level of pre-amplification hard wired in with no option to disable it.