Timing: Syncing Rack with External Synthesizer

VCV Rack
1

I had not tried it before, so I loaded up a CC-MIDI module to see if I could control my Behringer Neutron with the SEQ-3. After some fiddling with the Neutron to get its oscillators in a usable range, it … worked.

Next, I loaded up a KNOCK drum module to add a bass thump, also triggered by a step on the SEQ-3. At this point I noticed that the KNOCK and Neutron were slightly out of SYNC. If I put a Bogaudio CV delay between the SEQ-3 and KNOCK, I can more or less dial in the timing.

Is there any way to know, upfront, the amount of time compensation Rack and an external device will need?

1 Like
2

Yes, try to set sample delay according to the buffer size selected in your Audio module.

3

I found these figures on Sweetwater’s website in an article about latency:

At 44.1kHz sample rate:

32 samples = 0.73ms delay
64 samples = 1.45ms delay
128 samples = 2.9ms delay
256 samples = 5.8ms delay
512 samples = 11.6ms delay
1,024 samples = 23.2ms delay

At 96kHz sample rate:

64 samples = 0.67ms delay
128 samples = 1.35ms delay
256 samples = 2.7ms delay
512 samples = 5.8ms delay
1,024 samples = 10.7ms delay

I’m running at 48kHz, so I guess I will extrapolate unless someone knows of a calculator.

4

Ehm, just do 1s/48000Hz*<numberOfSamples>.
No calculator needed…

5

OK, well this is not what I was expecting. At 48kHz/512 samples, I would have imagined that I would need to introduce about a 9 or 10ms delay to the gate going to the CC-MIDI and then to the Neutron to align it with the gate going to the KNOCK kick in Rack.

It actually takes about 10 times more delay, about 1/10 of a second.

6

Yes, the calculation you provided returns the expected ~1/100 of a second.

Yet it takes ~1/10 second delay to align the beats.

7

Then there must be something different introducing this large latency. Can you describe the whole signal flow out of Rack and back in again?
Are you using something like ASIO4All?

8

I’m using WASAPI on Windows 10 right now. I can try it with the ASIO driver that came with my PreSonus USB audio interface.

In Rack, I have a clock from CLOCKED going to the SEQ-3. From there, the GATE output is connected to both the GATE IN on KNOCK and the GATE jack on the CC-MIDI. The Neutron is connected to the computer via USB.

EDIT: Yes, the PreSonus ASIO is faster. About 30ms. Also, I should note that I am using a fairly ancient computer … if that matters. i7-3770 3.4GHz.

EDIT-EDIT: I guess I don’t actually care — I’ll just line 'em up by ear. :stuck_out_tongue_winking_eye: