Topic: Distortion problem one channel at 192 kHz

I have a MADI HDSPe card with the latest driver 4.38 and two ADI-642 MADI to AES peripherals. A third 642 spare is available and I've used it for debugging. I so rarely work at 192 kHz, but I have not been able to work at 192k for a very long time. Using an external ADC/DAC converter pair I send audio out 2 channels of a 642 to a DAC for analog processing and then back to the ADC which returns on two channels of a 642.

Things work fine at 96 kHz. The problem at 192k is sometimes distortion on the right channel, or considerable white noise measuring around -56 dBFS on the digicheck meters in both channels. Clearly that is that white noise that I hear. I always see the noise on the ADC return at around -56 dBFS in Sequoia. Strangely, the noise is visible but it is inaudible if I route it to my monitor DAC. However, if I route the ADC return to an RME loopback, and then to the monitors, then I can hear the white noise quite obviously.

Measurements correspond with the noise issue. The ADC return measures around -110 dBFS in Digicheck's bit statistic and noise meter and this is inaudible. But as I said, the ADC return shows around -56 dBFS on both channels in Sequoia. Only if I route the ADC out to an RME loopback channel and then return it -- then I can hear and see the noise and Digicheck measures around -56 dBFS on the loopback return, 20-20 khz. Again, all of this goes away at 96 kHz sampling. 

Wordclock is generated by the ADC on internal sync, goes to the MADI card and then the MADI card feeds WC to the 642s, which are all locked to word clock. Of course I am using 48k frame. The problem does not go away if I lock the 642's to MADI instead of WC.

I need to isolate this problem. Could it be the HDSP card (SMUX problem?). It can't be one of the 642s as I have a spare 642 and replaced one of them so far and the problem persists. I am wiling to buy another MADi card and test it if you think it might be the card.

Re: Distortion problem one channel at 192 kHz

I did some further debugging. I disconnected the external ADC/DAC and ran a single AES cable from a 642 output to a 642 input. The signal was clean and channels are properly going where they should at 192 kHz.

This exonerates SMUX and the MADI as far as I can see. But it DOES point to the possibility that the RME ADI-642 PLL is having trouble locking to the AES preamble from my external converter at 192 kHz. All lock lights are good however, but still this points to a problem. I've had exactly this problem with two different models of ADC/DAC, by the way.

Is there any other logical explanation?

3

Re: Distortion problem one channel at 192 kHz

The ADI-642 is built unchanged since 2006, its firmware is unchanged since 2006 (version 2.1), and I have never received feedback that the units have an issue at 192 kHz.

To further examine this we would need to know what the external devices are. Also the quality of the fed AES signal should be checked.

And from your description I am not sure the HDSPe MADI can be ruled out. Which version (PCB) and which firmware is this one running on?

Regards
Matthias Carstens
RME

Re: Distortion problem one channel at 192 kHz

MC wrote:

The ADI-642 is built unchanged since 2006, its firmware is unchanged since 2006 (version 2.1), and I have never received feedback that the units have an issue at 192 kHz.

To further examine this we would need to know what the external devices are. Also the quality of the fed AES signal should be checked.

And from your description I am not sure the HDSPe MADI can be ruled out. Which version (PCB) and which firmware is this one running on?

Thanks, Mattias, for your quick reply. Glad to see you are alive and well!

I've tried this at 192 kHz in the past with a Cranesong HEDD quantum. And recently a Grimm Audio UC-1. In both cases the ADC is the master clock. Currently the WC from the ADC is going into two 642's on high impedance with a T connector and then to the WC input of the MADI card where the WC is terminated. All the sync lights are performing correctly on the ADI-642 and everything is perfectly well at 96 kHz. Only at 192 kHz is there this problem.

When I go to the "About" menu it does not tell me which version PCB it is. All I get is "RME Hammerfall DSP. Windows XP/Vista/7/8/10 driver. Driver date 6/7/2021. Version 4.38." I'm not sure I can find it in Device manager. What kind of device does it show up as in Device manager?

Re: Distortion problem one channel at 192 kHz

I can't find the card anywhere in device manager. I must have hidden it from the operating system at some point? I can't find it in the sound control panel or the device manager and I looked thoroughly. If we are not 100% certain but it's possibly the card I'm willing to buy a new one from Sweetwater. And then have my old one repaired, if it was the card.

Re: Distortion problem one channel at 192 kHz

looking for the board version I can find the serial number in the HDSPe Flash update tool: HDSPe MADI (22694227). Firmware or "revision" is 33. Maybe that's the board number.

Re: Distortion problem one channel at 192 kHz

Dear Mattias: Haven't heard from you in a few days. I have an extra ADI-642 unit and substituted it and got the same symptoms, so hopefully the problem is in the MADI card. If I purchase a replacement MADI card from Sweetwater will it be new stock, a later PC board? Thanks.

8

Re: Distortion problem one channel at 192 kHz

Thanks for all the information. You have the latest driver, and also the latest firmware in the HDSPe card (v33). And I don't think this is an issue of the card being defective.

The card should be visible in the Device Manager, under Audio, Video and Sound controllers. It's there anyway, otherwise it wouldn't work.

To further track this down I like to come back to your first description - the external DAC-ADC loop. The 642 has phones monitor, which can easily be routed to any input channel. If you have distortion on one channel use that tool to check that the 642 does not have (or has) this distortion at its input. If so then check the ADC's output on another receiver. If it's ok there plug it back to the 642. Distorted there then this would strongly point to an issue with the 642 AES receiver.

Another possible issue could be the Matrix having some overlooked routing active that causes issues. Not very likely, as the Matrix is not a mixer, and you should get immediate full level feedback when doing so. Still it might be an idea to use the MIDI Remote app to get a full view on all active routings.

In the same way you should check that TotalMix doesn't have any overlooked routings for the MADI card. Here, due to level control, feedback can indeed be metallic sounds, depending on the level.

HDSPe MADI cards should be in stock, as updated version with a new FPGA and therefore different firmware number (210). No changes or fixes that would explain your issues, though.

Regards
Matthias Carstens
RME

Re: Distortion problem one channel at 192 kHz

Thanks, MC. I will check. Today the problem is just the high noise level and the distortion issue has stopped.

Take care,


Bob

10 (edited by ramses 2022-09-02 14:06:28)

Re: Distortion problem one channel at 192 kHz

Hi Bob (or should I say Mr. Katz),
glad to see it has improved, although it sounds like it has changed now “out of the blue” or did you change something in the setup/routing?
I don't mean to intrude on Matthias' excellent support and knowledge here …. I can't give an exact technical reason for this, pure gut feeling: I would try out if changing the MADI frame size from 48 to 96k causes a change. Even if you find that it doesn't change anything, that would also be a statement that you know it's not related.

BR Ramses
UFX+, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1650v4, Win10Pro22H2, Cub12Pro

Re: Distortion problem one channel at 192 kHz

Well, I thought I had it fixed, isolating it to the manual I/O setup mode of the ADI-642 when at 192 kHz. But I was wrong, once I got the manual I/O correct, the distortion and noise returned at 192k. I'll check in headphones on the 642 monitor now. Stand by, please.

Re: Distortion problem one channel at 192 kHz

The distortion is present in the phones monitor of the ADI-642 as well. I checked all stages of the route and it is distorted. Some kind of clocking or locking problem?

13

Re: Distortion problem one channel at 192 kHz

Your setup is a big ring, so the final proof that the AES signal at the input of the 642 is undistorted is still missing. A simple way to do so is use another 192 kHz AES to analog converter and a simple XLR splitter to attach the ADC output signal to the 642 in the ring and the monitoring device simultaneously. That one then can tell us if the 642 is the culprit or the whole setup has some unidentified clock issue.

Regards
Matthias Carstens
RME