Differing latency using two different aggregated interfaces

[rlcartwright]

Hi All:

I use my Metric Halo ULN-8 3D pre/interface for remote recording with my late-2016 MacBookPro (TB3 + USB-C). I wanted to find a way to backup (mirror record) on to another device that would work standalone, without the ULN-8 or a computer, so I found the new Sound Devices MixPre-10T. I’ve used it to backup record, and I compared the mic pre with the ULN-8 (expecting to have a slight decline in audio quality) and found it to stand up very well. So far, so good - I could backup record on a completely separate standalone recorder in case of ULN-8 or computer problems.

I also want to use it as an aggregate device within DP9.51 when I need more than eight tracks at a time, and have been checking it out for that usage. It works fine, except that there is a latency difference between the ULN-8 and the MixPre-10T in the DP-printed tracks. I’m not talking about the latency caused by going through the computer and DP software, but different latency in the tracks being printed to DP. Both devices have zero-latency listening where it picks off the audio signal before the conversion and computer and sends it to the headphones immediately. My problem is that the printed MixPre tracks are between 256 and 430 samples late in the DP project. This is between 6.7 to 9.7 milliseconds. Obviously, I would have to keep individual instruments on either the ULN-8 OR the MixPre so that, for instance, both sides of a stereo track would have the same latency.

I’ve emailed the Sound Devices tech support (they’ve been very helpful) to ask about this and to see if it’s possible to write drivers (there are no drivers for the MixPre now) or firmware to achieve faster throughput, but I don’t know if it is possible to do. I know if I bought another ULN-8 it would solve the different-latency problem, but it would not be a recorder or standalone.

Is anyone else using a non-Metric Halo interface as an aggregate device with another brand of mic pre/interface? I have no idea what kind of latency others are experiencing in doing this. Other than figuring out the latency after the fact and shifting the MixPre tracks earlier, I can’t think of a solution. Unfortunately, the latency doesn’t seem to be always consistent, so I can’t just type in a set number of samples to advance the MixPre tracks.

An odd question, I know, but if anyone else has dealt with this, I’d love to hear how much latency other non-MH interfaces have and how you deal with it in DP9.51.

Thanks!

Robert

Robert Cartwright
perfectwavedigital.com
San Diego, CA