How low can you go (latency that is)

[Guest bassman7755]

OK so I've been messing about with various bits of kit trying to get a setup where I can play through VSt modelers etc and monitor and record on my DAW (studio one pro). I wanted to pursue this approach because of the obvious advantages of recording the dry signal but you really need to hear the effected sound as you play.

I've worked out a way to measure the real world total record monitoring delay on the DAW: I record a reference sound with a sharp attack (in my case just playing a picked note on my guitar) on two mono channels simultaneously, directly on one track which has monitoring switched on, and recording this monitored sound via a microphone on the monitor speaker to the other (turn monitoring off on that track for obvious reasons).

So channel 1 the signal path is
instrument -> audio interface -> daw
and channel 2
instrument -> audio interface -> daw -> audio interface -> speaker -> mic -> audio interface -> daw

I then use the timescale view to measure the difference in timing between the waveforms.

This has yielded some interesting and surprising results. In all cases I used the shortest ASIO buffer I could without audio glitches which was generally a combined input and output buffer latency of 4-5 milliseconds and had no VSTs running in the DAW.

Using a presonus VSL 22 USB interface my results varied from 11 to 18 ms (which subjectively equate to "bearable" and "intrusive" respectively) depending on which USB port I plugged into. This was the first surprise - that what port was used had such an influence, I can only put it down to different USB hubs on the motherboard having different polling frequencies or something. The lowest latency was when plugging into the "legacy" USB 2.0 ports.

For shits and giggles I then decided to see how my humble soundblaster X-Fi pcie card would measure up to the supposedly purpose built low latency recording presonus interface, and here was the second surprise, the X-FI turned in a blazing 5 ms complete round trip latency time i.e. it was adding almost zero extra latency over and above the base ASIO buffering delay.

So with the X-FI even when monitoring a daw channel through a typical guitar processing chain e.g. amp sim - delay - reverb my total latency is 7 odd ms (subjectively "barely detectable") so a result there. At this sort of latency it feels like playing though a hardware amp sim like a pod if not slightly better.

Now some observations on how VSTs affect latency. Studio one has a very nice feature where it tells you max processing delay that your active effect plugin chains are causing. Amp sims seem to range from 0.5 to 2 ms (towards the latter mostly when your using a cab sim as well), reverbs delays etc add no additional latency, neither do dedicated E.Qs or tuners or any of the other analysis plugins.

However beware compressors, limiters and gates and any plugin that has a compressor or gate built in such as a channel strip - these all added 2ms each. A bit of playing around suggested that this was due to these plugins generally doing a small "look ahead" to process the signal - I came to this conclusion because if I use a compressor with a defeatable look-ahead the plugin latency goes back to 0 when I disable the look-ahead.

If only I had done this before buying the presonus interface ...

Hope this info is useful to someone.








I

[Greggo]

What are the specs of the PC you are running?

I've recently started using a better laptop to record and I'm recording dry and monitoring the wet signal same as you. The interface I'm recording with costs £20 and it gives me ridiculously low latency - it's a Rocksmith USB guitar lead!

Using WASAPI drivers set to 64 samples it's next to no latency and even adding on amp sims / cabinet emulators etc does not add much latency. No glitches at all sk far with up to 10 tracks Inc .

I think latency is low on the USB because the processing of sound is by the processor not the sound card absit's absolutely perfect for recording!

I've tried this on a 2.4ghz dual core and a 2.5ghz i5 and it's a spot on in both!

[Guest bassman7755]

[quote name='Greggo' timestamp='1437937322' post='2830208']
What are the specs of the PC you are running?

I've recently started using a better laptop to record and I'm recording dry and monitoring the wet signal same as you. The interface I'm recording with costs £20 and it gives me ridiculously low latency - it's a Rocksmith USB guitar lead!

Using WASAPI drivers set to 64 samples it's next to no latency and even adding on amp sims / cabinet emulators etc does not add much latency. No glitches at all sk far with up to 10 tracks Inc .
[/quote]

Its a very high spec PC, i7 4ghz, like you I'm running a 64 sample buffer.

[biro]

Interesting! However, after years of tinkering, I believe the short answer to the question in your title is: you can go low, but you can't get rid of it altogether -- which doesn't necessarily need to be a problem.