1 Topic by jvalenzuela

  • jvalenzuela
  • Initech programmer
  • Offline
  • From: Orlando, FL
  • Registered: 2007-10-10
  • Posts: 223

Topic: AES Noise

I was working on a system today and noticed a slight 'buzz', rather low in level, but noticable. I traced it back to an Nio AES input of all things. When I mute the mixer input that is fed from that AES input, it definitely fixes the problem. The funny thing is that nothing was currently attached to that input. If I look at the associated slot's tab in the NioNode, it shows the error LED on and the sampling rate and emphasis set to none, exactly what I would expect from a digital input not currently receiving anything.

2 Reply by ivorr

  • ivorr
  • ivorr
  • DSP Geek
  • Offline
  • From: West Des Moines, IA
  • Registered: 2007-08-17
  • Posts: 56

Re: AES Noise

It has been found that if an AES input is disconnected during operation, digital noise will result at the level the signal happened to be when it was disconnected. It is a known issue and is being addressed. In the mean time, I have developed a workaround.

Open the NIO-AES block on the NioNode's Schematic page > Show tabs > Show Schematic > open the Fix To Float block > Copy the two mute buttons associated with the input in question to a block > Copy the input's Audio LED into the block with the mute buttons. Give the Audio LED a master wiring node and slave nodes to the mute buttons. > Place a logical NOT device in the block > wire the Audio LED to the NOT input > wire the NOT output to the mute buttons. Save and recompile.

If audio disappears from the AES input, the LED will go out and the inputs will be muted.

Last edited by ivorr (2008-08-27 17:01:39)

The only true wisdom is in knowing you know nothing. -Socrates

ivorr's Website

3 Reply by JoshM

  • JoshM
  • JoshM
  • Recording Engineer at Burnt Orange Studio
  • Offline
  • From: Meridian, MS
  • Registered: 2007-08-13
  • Posts: 1,498

Re: AES Noise

I am going to offer a slight modification on Ivor's setup...

Do everything that he suggests, exactly as he suggests with these exceptions:

Do not use the "Audio" LED, use the "Error" LED, and there is no need for the logical NOT device.

This means that when there is an error (i.o.w. no input signal), the input is muted, but when the input is connected and receiving correct clock and data information, the error state will go away and thus the input will unmute.

Josh Millward
Burnt Orange Studios

JoshM's Website

4 Reply by draudio

  • draudio
  • Member
  • Offline
  • From: Glendale, CA
  • Registered: 2007-09-18
  • Posts: 32

Re: AES Noise

I have tried this, using the Error indicator, and I find that the response is not fast enough to completely eliminate the noise. I still need to use a ramp with a separate trigger to make sure I get no noise.

Has the root cause of this been addressed?  I know we don't experience this when using a CAB 16d...so why such a problem with the AES card. As it is, the card is not really usable...but it's too late in the project for me to swap it out now!

Thanks!

Thanks!

Dave

5 Reply by JoshM

  • JoshM
  • JoshM
  • Recording Engineer at Burnt Orange Studio
  • Offline
  • From: Meridian, MS
  • Registered: 2007-08-13
  • Posts: 1,498

Re: AES Noise

A little update from the front on this topic...

There is an interesting behavior of the Sample Rate Converter on the NIO-AES card. When it loses the incoming clock signal, it continues to output the last bit that it knew was correct instead of transmitting silence. This is perceived by us as noise. This is why we get different amounts of noise when disconnecting a signal.

So, the nice thing is that it is possible to adjust the behavior of this via firmware modification to tell the SRC to output silence instead of repeating the last value. The really nice thing is that this is accomplished simply by updating the firmware in the NION. The cards in the card slots on the NION upload their firmware from the NION when the unit starts. So, with the next release of NWare, this fix will be implemented.

If you are currently experiencing a problem of this nature and need a fix now rather than waiting for the next release of NWare, please let me know. I will send you the Alpha release that has this fix in it. I provided this to Dave and have not heard back, so I assume that it has remedied his problem.

Dave- If you are still having trouble, please let us know so we can address it.

Thanks!

-Josh

Josh Millward
Burnt Orange Studios

JoshM's Website

6 Reply by kjhyland

  • kjhyland
  • Member
  • Offline
  • Registered: 2007-09-14
  • Posts: 2

Re: AES Noise

Josh:
Which version of NWare will fix this problem?

Thanks, KH

7 Reply by draudio

  • draudio
  • Member
  • Offline
  • From: Glendale, CA
  • Registered: 2007-09-18
  • Posts: 32

Re: AES Noise

I have installed the alpha version of the fix last week and it works well...no more noise and no side effects that I could find. This is on an Nx...

Thanks!

Thanks!

Dave

8 Reply by JoshM

  • JoshM
  • JoshM
  • Recording Engineer at Burnt Orange Studio
  • Offline
  • From: Meridian, MS
  • Registered: 2007-08-13
  • Posts: 1,498

Re: AES Noise

kjhyland wrote:

Josh:
Which version of NWare will fix this problem?

Thanks, KH

Kevin-

This fix will be rolled into the upcoming NWare 1.5.1 release. This release will be out before InfoComm09.

It looks like NWare 1.5.1 will have quite a lot of updates and fixes for things in it. You will want to be sure to read the release notes when it is made available.

If you have a system that is currently problematic, I can send you the same firmware I sent to Dave. We tested it here and it fixed the problem, and Dave tested it with the system that was problematic and it fixed his issues too. So, I'd say it seems like it is fixed.

Last edited by JoshM (2009-05-06 21:56:45)

Josh Millward
Burnt Orange Studios

JoshM's Website