• Registered: 2011-11-02
  • Posts: 57

Topic: Digiface and Mac Mini - Round Trip Latency

Despite some extensive searching in this and other forums I can't seem to find many real-world reports of the the ROUND-TRIP latencies achievable with a Digiface.

I'm thinking of getting a Digiface (with HDSPe ExpressCard via Sonnect Echo Express Thunderbolt adapter) running off a Mac Mini Server (Core i7-2635QM 2.0 GHz Quad-Core).  The Mac Mini is roughly equivalent in power to a current generation MacBook Pro.

My converters are Prism Orhpeus and Steinberg MR816, which I'll be running off ADAT into the Digiface.  I'll be using Logic as my DAW.

I'd be interested to hear from other Logic users whether they think I'll be able achieve a ROUND-TRIP latency of no more than 5ms or less?  What round-trip latencies are other people getting with their MacBook Pros/Mac Minis, or similar?

My other option would be to get a Raydat with an entry level Mac Pro (Xeon "Nehalem" W3530 2.8 GHz Quad-Core) but I need to spend money on other gear if I can.

Logic 10.7.2 - macOS Monterey 12.7.5
HDSPe Digiface via ExpressCard Adapter
Fireface UFX III & UCX I
  • From: Houston, TX
  • Registered: 2007-05-11
  • Posts: 1,191

Re: Digiface and Mac Mini - Round Trip Latency

A Digiface will have an inherent DIGITAL I/O latency of 96 Samples when using 32-Sample ASIO Buffers (32 in, 32 out, 32 Safety Buffer).  Add any latency your DAW might add (should be close to zero assuming no latent plug-ins are used in the session) and the conversion latency of your converters - and that's your RTL on any platform (MAC, PC, Laptop, etc).

I believe it has been stated that the Thunderbolt PCIe adaptors don't add any measurable RTL latency.

Now, how much DSP load a system can handle at 32-samples will vary wildly.  I DIY some pretty serious PC's to be able to cope with larger sessions with lots of I/O and VST's at 32-Samples (4GHz i7 Quad Cores and beyond!).

So, the platform itself shouldn't affect the RTL that much (Digiface on a Mac Mini vs a Raydat on a Mac Pro vs MADI HDSPe on a DIY PC) - but how much horsepower you will actually end-up with at 32-Samples will be what determines your computer hardware requirements IMO...

cool

MADIface-XT+ARC / 3x HDSP MADI / ADI648
2x SSL Alphalink MADI AX
2x Multiface / 2x Digiface /2x ADI8

3 Reply by DanRand (edited by DanRand 2012-01-20 02:12:19)

  • Registered: 2011-11-02
  • Posts: 57

Re: Digiface and Mac Mini - Round Trip Latency

Thanks for that info.

However, I'm a bit confused about the safety buffer in Logic (which I'm new to).

In the Digiface manual it's stated that "Under OS X...The Digiface uses a safety offset of 32 samples. This offset is signalled to the system...".  But Logic also has an I/O Safety Buffer checkbox, which can be switched off.

Is the "safety offset" in addition to & separate from Logic's I/O Safety Buffer?


EDIT:

Just found out that the I/O Safety Buffer is gone in Logic 9, so no need to answer that.

However, is the safety offset [buffer] applied to BOTH input AND output (i.e. 2 x 32 = 64 samples)?

Also, does anyone know the hardware latency that's imposed/incurred with the Digifaces input and outputs?  Obviously, there will be no AD/DA converter latency added by the Digiface itself.

Logic 10.7.2 - macOS Monterey 12.7.5
HDSPe Digiface via ExpressCard Adapter
Fireface UFX III & UCX I
  • From: Houston, TX
  • Registered: 2007-05-11
  • Posts: 1,191

Re: Digiface and Mac Mini - Round Trip Latency

Just as stated above.  The safety buffer is a playback buffer IIRC, and only affects the RTL with a single instance.  32 Samples In, 32 Samples Safety Playback, 32 Samples out.

I don't believe ADAT itself adds any further latency, but if it does, it can't be more than a sample or two...

As a reference, I think I recall my Multiface (analog version of Digiface) reading RTL's of 3.1x ms RTL (or so) with the 32-Sample Buffer using the Centrance RTL tester.  Well below 5ms with the RME converters which aren't all that fast on the Multiface (I believe your 816 has lower conversion latency than the AD/DA's on the old MF-I, but won't be a drastic decrease)...

With regard to Logic's buffers - I have no clue, but sounds like you got it figured out...

cool

MADIface-XT+ARC / 3x HDSP MADI / ADI648
2x SSL Alphalink MADI AX
2x Multiface / 2x Digiface /2x ADI8