Latency measurements for 16 input recording with Tascam USB 2.0 interface

[des0free]

I've been experimenting with a USB interface for recording live performance with Reaper with only software plugins for all FX (first mentioned here: https://songcrafters.org/forum/index.php?board=88.0), and a relatively cheap but new Acer Swift 3 i5-1135G7 laptop. The setup seems to have sufficiently low latency for real time tracking.

I did some measurements of the latency. I really just want a set up where I can record guitar and mic playing along to backing tracks (e.g., see: https://songcrafters.org/forum/index.php?topic=32997.0)

But since the interface has 16 channels I was curious to test recording all 16. I recorded a click track and then played it out and then back into an input channel and recorded it, and measured the delay. This is with a Win10 laptop with everything possible uninstalled or turned off (e.g., no antivirus, no wifi). Using 96 kHz/24 bit and a 64 sample buffer (I think about the lowest before you start to get glitches), I measured ~6-7 ms. Turning on/off hardware (DSP) EQ and compressor didn't change this. If there is a 64 sample buffer on both input and output then ~1.2 ms of would be the buffers (2*64/96000), so ~5-6 ms must be the USB and/or computer speed. Interestingly recording all 16 channels simultaneously doesn't slow it much, so maybe it is mostly "overhead" in the drivers.

I then added EQ and compressor input VST plugins (the basic ones free in Reaper) to every channel and the master track, and a track with a reverb VST (free Voxengo "old school verb") with all 16 channels routed to it, and those don't slow it much. Then I put an Amplitube 5 "American Tube Amp (with spring reverb)" VST on one channel and that alone added about 2 ms, so that VST runs much slower than the others. But adding it to two other channels did not increase this, probably because the laptop has 4 processors/8 threads? So in the end, regardless of whether you record 1 vocal + 1 guitar with amp sim, or 16 channels with 3 amp sims, the overall latency is ~8-9 ms. And that seems tolerable for real-time monitoring (though I read that some people claim to be bothered by latency as little as ~2 ms). (* I'm assuming that the VSTs run at the same speed regardless of whether or not significant signals are going into them, because I only have the click signal going into one channel while the rest are recording nothing/just noise...)

[Flash Harry]

Interesting.

I've used Reaper for quite a few years with a Scarlett 8i6 and an XAir18.I've not had latency issues that I can recall - I have had to fiddle with the monitoring on a cheap Behringer adaptor, but it's not a biggie.

I have recorded all 18 channels from the XR18 simultaneously into a really old old laptop that I put an SSD into - it seems that disk speed is far more important.