Hi,
A friend of mine, professional user of Reaper, found something to make it work on Surface Pro 4.
The problem seems to come from the Windows Mixer.
If I tell Windows in the notification area to use the Surface pro 4 builtin speaker (Realtek High Definition Audio) instead of the iRig Keys outputs, suddenly, the cracks disappear and I can use UVI Workstation and Miroslav Phliharmonik in Reaper with no latency at all, in ASIO4ALL at 128 samples.
The surface pro 4 core m3 / 4GB and this iRig Keys 49 alone allowed me to perform live yesterday. It's a really interesting, lightweight, fully configurable setup that only needs the irig Keys 49 bag for transport, because the surface pro 4 has the perfect size to fit inside, below or on top. Here are some pics of the setup on stage :
https://photos.app.goo.gl/4d2uMtHMToM4NSR48
You just have to get the surface pro 4 integrated support to go behind the irig iPad support because the surface pro 4 is just 1,5-2 mm too wide to stand in it (see last photo). Then it stands perfectly.
The only problem I encountered was on extremely complex sounds : the power of this version of surface pro 4 couldn't manage a big polyphony (above 50) or a lot of effects. That said, I could use EQ, Drive, SparkVerb and Delay easily on multiple sounds from UVI Augmented Piano and PX V8. Sounds from IK Multimedia are easier because they often are a lot lighter for the CPU and RAM.
Overall, you can have equivalent sounds than those of a Nord stage Clavia for a third of the price and a tenth of a weight !
Has anyone tried this ?