Strange waveform

[Resolectric]

I was performing a test to check for the inconsistencies in latency that exist in USB interfaces (16rig included) but while testing i was surprised by the strange waveshape that resulted from a single-sample recording with 16rig.

Let me try to explain, step by step, what i did:

1. i first created a single-sample audio file at 96KHz/24bit. The file has a level of -3dB and, as i said, only lasts for one sample.
   It is a positive half-wave only (green track).

2. i inserted this file repeatedly (as a sequence of short clicks) in one track of Magix’s Sequoia 17.

3. plugged a balanced jack cable connecting Output 10 to Input 16 of 16rig and enabled the “Pad” in input 16 otherwise the level would be too high.

4. Played the single-sample sequence in the first track and recorded in a second track.
   The result is the Yellow track in the middle.

5. Then changed ASIO interface in Sequoia into MOTU’s 24i/o and conneceted Output 20 to Input 20 with the same balanced cable used before.

6. Repeated the test but now with the MOTU 24i/o recording into a third track in Sequoia.
   The result is the brown track in the bottom.

There is something wrong with the waveshape resulting from the Arturia recording.
I have repeated the test with Nuendo 13, repeating the exact same steps and with the same original single-sample file.
The results were the same.

The sample recorded by Audiofuse 16rig displays a clear and very scary difference: there is a decay in the waveshape.
It’s not a sharp sample anymore, it became a decaying sawtooth.

Am i doing something wrong here or did Arturia do something wrong?

EDIT:

Just in case someone argues it might be the Input PAD being enabled that is affecting the shape of the sample, here’s the result without Input Pad (disengaged).
The channel 10 Output had to be reduced by -6.73dB to avoid saturating the input.

[Resolectric]

It later occurred to me that another cause for this problem could be a clocking issue so i performed the same test but this time clocking the 16rig from an External Clock.
The MOTU Digital Timepiece was used.

Unfortunately the problem persists.
The audio recorded by Audiofuse 16rig is severely deteriorated and does not represent the input signal in any way.

[Resolectric]

Same test settings but now with a continuous wave.

Top (green) is the original wave.
Middle (orange) is the direct Out > In for Audiofuse 16rig
Bottom (brown) is the direct Out > In for MOTU 24i/o

Sine:

Square:

Either i have done something wrong or Arturia made faulty interfaces.
I suggest everyone to replicate these very simple tests as, apparently and judging from the results, the 16rig is creating defective recordings.

[valdpsr_arturia]

Hello Resoloctric, I hope you’re doing well,

Valentin from Arturia’s R&D department here

Thank you for reaching out to us and for providing such a detailed explanation of your test process. We truly appreciate the time and effort you’ve taken to investigate this.

We’d like to reassure you that the behavior you’ve observed is not an issue but rather an expected result of the PCM filter implemented in the DAC of the 16rig.

The choice of a PCM filter is a complex and broad topic. For the 16rig, we carefully selected a design that prioritizes the best possible latency, excellent flatness across the audio range (20Hz–20kHz), and a minimization of artifacts such as pre-ringing. These choices ensure optimal performance and sound quality for the majority of use cases.

The differences you’ve observed compared to the MOTU 24i/o interface are likely due to the distinct DAC design or PCM filter trade-offs made by MOTU, which reflect their own design goals and priorities.

We encourage you to explore the topic of PCM filters further if you’re interested, as it’s a fascinating area with many design considerations and trade-offs to balance. It might provide additional insight into why these differences exist between products.

If you have any further questions or need additional clarification, please don’t hesitate to reach out. We’re here to help!

[Resolectric]

Hi Valentin!
Thank you very much for the reply and the interest demonstrated in the topic subject and my tests.

I am aware of certain details of the techniques you mention but wasn’t at all aware of their implementation in 16rig or the effect they have in this specific case.

I will not extend the topic so that your reply doesn’t get lost with further posts.
I will gladly continue participating in the forum, now even more so, knowing that you and other engineers at Arturia really do pay attention.

Next test I’ll probably report is not Arturia specific but relates to all USB interfaces, where inconsistent latency is a measurable problem.
Hoping to find answers!

Thanks again for your reply, wishing you and yours a magnificent 2025.

–

Paulo

[derriz]

Hi @Resolectric - interesting analysis. Is there some way of seeing the scale of the x-axis (time) in the above sine and square comparisons - or what sort for frequencies are the test signals?

[Resolectric]

Hi @derriz .

Both the Sine and the Square waves are 220Hz -6dB at 96KHz Sample Rate.
Forgot to include the info. Thanks for noticing and asking.
They were generated inside Sequoia with its “Waveform Generator” tool.

According to @valdpsr_arturia 's post the ripple is due to the type of DAC filter used in 16rig wich i assume is a Minimum Phase filter.