Reaper Routing to 1/2 signal leak problem

[numina]

Hello there,

I am breaking my head about a bus problem I'm having using Reaper on
Windows 10 with both my MOTU ultralite-mk4 and the TASCAM 16x08.

Using a normal stereo master bus, I am not able to pan completely to the left or right in the sense that I will always still hear the signal in the other channel. Also when I pan the concerning channels (for example Computer USB1 and Computer USB2) inside the MOTU Control mixer to left and right the signal is still leaking to the other channel. My workaround right now is that use Computer USB1 as the left channel inside reaper and pan that one to the left inside MOTU and then use Computer USB3 for the right channel inside
reaper and pan that one to the right inside the MOTU Control mixer, but
this is a quite annoying workaround. I haven't been able to find the
solution online. Somehow these channels seem to be paired - so I'm
wondering where I can switch this off.

When I use my Tascam 16x08 I have the same issue, when I use Reaper: the signal is leaking i.e. to the right whenever I'm panning completely to the left. When I use 3/4 of the TASCAM as the master stereo, then I have full separate panning behaviour/.

When I test with Pro Tools, I don't have this issue: outputs 1/2 on both the Tascam and MOTU have normal full panning behaviour. So there's some problem with Reaper.

I am really breaking my head on this one. So any help / advice, would be appreciated. Thanks in advance.

n

[SoundGuyDave]

Obviously, you need to get a control to test with. Download a mono sine wave (400HZ or 1kHz, doesn't matter) from the interwebs, and in a fresh project, confirm the behaviour. I've been caught out on "stupid things" before, like weird panning response because I forgot that I had a plug set to M-S rather than L-R....

If you can confirm panning problems with the mono sine signal, then I would start looking at the hardware drivers.

[numina]

Thanks, Dave. Apologies for not mentioning this - this was indeed tested with a mono sine wave in a fresh project. Yes, it might be a problem with both the MOTU and Tascam ASIO drivers.
I have been in touch with the MOTU support about their native MOTU asio driver, but since the problem only occurs with Reaper - they told me to look at the DAW. So I'm a bit stuck here.
Don't want to switch to another DAW obviously, since I love Reaper.

[SoundGuyDave]

Hopefully one of the IT gurus can offer comment... I just wanted to eliminate the obvious!