• Registered: 2021-03-09
  • Posts: 27

Topic: which interface offers the pot. lowest RTL?

Setup MacBook Pro 2020, Main Stage, Guitar Rig, Logic etc
My main application is playing live with a range of VST/AU plugins and I want to know whether I get lower RTL with the Babyface Pro FS or the UFX+.
I know the BF has faster ADC/DAC, the UFX+ TB connection. Which minimum RTLs can be expected with 32samples 192 kHz? Would also be interested in how the UCX compares to these figures.
(is there a comparison somewhere, listing potential RTLs of a range of RME interfaces?)

2 Reply by ramses (edited by ramses 2021-03-09 20:06:50)

  • ramses
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  • Registered: 2012-10-14
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Re: which interface offers the pot. lowest RTL?

Please search forum (extended search) for RTL and my name. You will find several hits like these:

https://forum.rme-audio.de/viewtopic.ph … 21#p166621
https://forum.rme-audio.de/viewtopic.ph … 82#p166282
https://forum.rme-audio.de/viewtopic.ph … 22#p166122
https://forum.rme-audio.de/viewtopic.ph … 00#p165800
https://forum.rme-audio.de/viewtopic.ph … 59#p165659
[.. and more ..]

It will explain a lot in that regards and point you to some interesting information in blog articles that I wrote.
https://www.tonstudio-forum.de/blog/ind … Cbersicht/

In the UFX+ blog article (https://www.tonstudio-forum.de/blog/index.php/Entry/68-RME-UFX/ ) you'll find the RTL round trip latency of different RME recording solutions:
https://www.tonstudio-forum.de/index.php/Attachment/2343-UFX-UFX-RayDAT-Latencies-v2-jpg/


If your budget allows .. go UFX+ !!! This is the flagship interface, the best package on the market available in regards to every aspect you might want / need for smth like a recording interface and very scalable by MADI.

This is the way I work ....
https://www.tonstudio-forum.de/blog/ind … -DURec-DE/

... and here my current setup .. combination of Recording and HiFi corner.
"Corner stones" of this setup: UFX+ / 2x ADI-2 Pro FS R BE (Includes also a mobile setup)

This is meant only as a "real world" scenario, how versatile you can combine RME components.

https://www.tonstudio-forum.de/index.php/Attachment/2703-05-UFX-in-Current-Setup-jpg/

List of USB/FW/TB interfaces, see my excel, here you can compare technical data and other information that I collected from forum and manual:
Blog article: https://www.tonstudio-forum.de/blog/ind … B-MADIfac/
Direct link to Excel: https://www.tonstudio-forum.de/index.ph … 0-08-xlsx/

Briefly in terms of your low latency requirements:
- RME ASIO driver are written so well that it doesn't matter much, which one you choose
- the RTL across USB/FW/TB is bigger compared to converter latency
- playing guitar over a virtual amp (Kuassa VSTi) I still get managed with UFX+, ASIO buffersize of 256 and RTL of around 13ms

Will all RME solutions you will stay below 10ms with an ASIO buffer size of <= 128.

Note: recording at 192 kHz is overkill and not required, it only puts more stress to your system (CPU, I/O) bigger files ...

I am recording at 44.1 and am still very satisfied. This CD-Quality.
For high quality music with very high dynamic (Classic, Jazz) I would choose 88.2 kHz.
There are some esoteric discussions about, that some VST should sound better with double speed (88.2/96).
If you think so ... do it .. but 192 kHz ... I have doubts about the usefullness and also most VSTi do not support this..

Please take your time and "digest" this information, later we can talk about your concrete budget and requirement to put together a nice solution for you.

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13
  • Registered: 2021-03-09
  • Posts: 27

Re: which interface offers the pot. lowest RTL?

Thank you Ramses, for your thorough reply!

ramses wrote:

I still get managed with UFX+, ASIO buffersize of 256 and RTL of around 13ms

13ms would definitely be too much for me, I'd like to end up at not more than 5ms
And of course, for recording the live-stuff I would never need a high sampling rate,  I just thougth of 192kHz for minimizing the RTL. BTW is there a possibility to engage the DURec function with downsampled data, e.g. let the UFX work with 192kHz and record with 48kHz. Or send to the DAW just a 48kHz data stream? Or would that need an extra step afterwards?

Other question regarding the Babyface (or ADAT ports in general). When I use an ADAT 8-channel expansion, like the Focusrite Clarett OctoPre, are the 8 ADAT channels imposed with a little processing delay because of the serial ADAT data stream? Plus the ADC/DAC time that could be longer than the ADC/DAC time of the Babyface built-in channels?
In other words, can the ADAT channels result in another RTL than the Babyface built-in channels?
Thank you !

  • ramses
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Re: which interface offers the pot. lowest RTL?

VayouApp: 13ms with an ASIO buffersize of 256 was only meant as an example, how well the RME drivers are written and to show you  how low RTL with RME is even at 256 sampels ASIO buffersize..

From the overview you can see, that UFX+ RTL is 2.6 and 3 ms (USB3/TB) with the lowest ASIO buffersize that the MADIface driver allows which is 32 samples, like with the HDSPe drivers.
The older ASIO driver for USB and Firewire have 48 samples as lowest value.

BTW .. its IMHO not worth to record with 192kHz with the sake of reducing RTL.
Converter latency is so  much smaller compared to the time that it takes for the transfer over PCIe/USB/FW/TB.
Check yourself in the manual, for my UFX+ this is documented in chapted 40.2
https://www.rme-audio.de/download/fface_ufxplus_d.pdf
https://www.rme-audio.de/download/fface_ufxplus_e.pdf
There you can find the converter latency for severy sample rates
AD and DA @44.1 kHz: 0,28   + 0,16   =  0,44ms
AD and DA @192  kHz: 0,052 + 0,036 =  0,088ms
The difference is only 0,35ms

Compared to the whole RTL at different ASIO buffersize you can ignore this little difference.

> In other words, can the ADAT channels result in another RTL than the Babyface built-in channels?

The ASIO driver doesn't know the converter latency of devices connected through ASIO.
There will be a very small delta that you do not need to be worried about.

BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13
  • Registered: 2021-03-09
  • Posts: 27

Re: which interface offers the pot. lowest RTL?

Thank you for these numbers! May I ask once more to get a better understanding of what all makes up the RTL?
As I see, your UFX+ RTL table is made at 44,1 kHz

Buffersize 32 * 1/44100 = 0,726ms
Does this have to be counted 2 times for -> into PC -> Processing ?ms -> out of PC ?
This would give >= 2 * 0,726 = 1,45 ms as the theoretical minimum RTL for 32 samples at 44,1 kHz ?
So the difference of 2,612 and 1,45 = 1,16ms is the time needed for TB-interfacing and CPU processing?

for Buffersize 512 * 1/44100 = 11,6ms
times 2 = 23,22ms
24,332 - 23,22 = 1,112ms is fairly similar

does it go like that?

shouldn't  these numbers be even smaller at 96 or 192kHz at 32 samples? (given that the used plugins, CPU etc.  can handle the audio stream continuously = crackle free)

I just want to understand it properly, so thank you very much again!!

6 Reply by torbenscharling (edited by torbenscharling 2021-03-15 00:55:44)

  • Registered: 2019-02-14
  • Posts: 148

Re: which interface offers the pot. lowest RTL?

The latency is different on the input vs output, so you can't just "count it 2 times" (usually output is slower than input latency, at the lowest buffer sizes at least)
Yes, the numbers are smaller at higher Khz, but neglible, as it's below 0.XX samples and you have to take into account the buffer size doubles when you double in Khz..you can go to 32 buffer at 44 but not at 192, regardless how beefy your PC is wink

  • Registered: 2021-03-09
  • Posts: 27

Re: which interface offers the pot. lowest RTL?

Thank you!
Slowly it's getting clearer...

Does anybody know, is RME working on an updated version of the UCX? The model is getting 10 years old...