Noise, dropout questions (long post)

[Ed Snape]

This is more in the realm of hardware and was originally posted to the RME forum, but many of you have the knowlege to help.

I do symphony orchestra recording with minimalist(4)mic techniques. The last 3 recordings have been marred by tick, spit noises occurring every few minutes. The noise occurs on all 4 tracks. Examination of the waveforms does not reveal any spikes, but rather a series of distorted waves of the same amplitude as the program. On occasion, use of RME HDSP meter bridge has caused numerous and continuous spitting noise under the same conditions. The noises can be heard on Digiface analog out monitor during recording, and are recorded in Saw Studio. They did not seem to be present in the SPDIF output upon spot checking.

THE SETUP

HP ZD7000 laptop, XP professional sp2, RME Digiface & Cardbus, RME Octamic, Behringer Pro 8. DSP mixer and SawStudio used to record 4 tracks only.

Digiface set as master wc generator, Octamic and Pro 8 set to slave to Digiface. Indicated processor load never exceeds 4%. HDSP buffer size 512. SawStudio output and input buffers set to 4 @512 samples.

I have read RME’s laptop optimization suggestions but they seem to be specific to Win98 and 2K. Any XP optimization instructions?

In my own effort to troubleshoot this problem I noticed that I had left numerous unused input and play faders open in the DSP mixer. Even after all of these were closed, there was still a continuous dithering of the digital level indicators on unused input and playback channel strips. I then went into SawStudio setup and switched unused output assignments to “none”. This stopped the dithering of the mixer level indicators. So, did all these unwanted inputs load down my system to the point of introducing noise or dropout?

What other suggestions can you give?

Thank you, Ed

[Leadfoot]

This is more in the realm of hardware and was originally posted to the RME forum, but many of you have the knowlege to help.

I do symphony orchestra recording with minimalist(4)mic techniques. The last 3 recordings have been marred by tick, spit noises occurring every few minutes. The noise occurs on all 4 tracks. Examination of the waveforms does not reveal any spikes, but rather a series of distorted waves of the same amplitude as the program. On occasion, use of RME HDSP meter bridge has caused numerous and continuous spitting noise under the same conditions. The noises can be heard on Digiface analog out monitor during recording, and are recorded in Saw Studio. They did not seem to be present in the SPDIF output upon spot checking.

THE SETUP

HP ZD7000 laptop, XP professional sp2, RME Digiface & Cardbus, RME Octamic, Behringer Pro 8. DSP mixer and SawStudio used to record 4 tracks only.

Digiface set as master wc generator, Octamic and Pro 8 set to slave to Digiface. Indicated processor load never exceeds 4%. HDSP buffer size 512. SawStudio output and input buffers set to 4 @512 samples.

I have read RME’s laptop optimization suggestions but they seem to be specific to Win98 and 2K. Any XP optimization instructions?

In my own effort to troubleshoot this problem I noticed that I had left numerous unused input and play faders open in the DSP mixer. Even after all of these were closed, there was still a continuous dithering of the digital level indicators on unused input and playback channel strips. I then went into SawStudio setup and switched unused output assignments to “none”. This stopped the dithering of the mixer level indicators. So, did all these unwanted inputs load down my system to the point of introducing noise or dropout?

What other suggestions can you give?

Thank you, Ed

I have had similar clicks and snaps using HDSP 9652 and behringer ada8000.
But, only on the channels 1 & 2 for example, which just happened to be the ones that were used for outputs to the monitors. In other words, say I'm recording 10 tracks of drums, hardware channels 1 thru 10.. and my main outs going to my monitors are on outs 1 & 2, those are the tracks that had the snaps and crackles. I never could figure why that was, so I just started using channels 15 & 16 on the 2nd Beri, for monitoring since I usually never have that many recording ins at once. No more crackles.. but still that should not happen. I don't know if it's a problem with the Rme or the behringer at this point. Don't know if that helps you, but you never know. Thought it was worth mentioning. Thoughts, anyone?
Tony

[MMP]

I have heard slightly bad clock sync appear as ticks on one pair of inputs on ADAT lightpipe devices. No sync light error, but still out.

I would test all possible clocking combos to see if one is more stable than another.

Regards,

MM

[Naturally Digital]

Hi Ed,

Hmm... spit noises does sound like a sample rate issue. Either a sync or one of the devices actually operating at the wrong rate (48K vs 44.1).

Just a thought.
Dave.

[Craig Allen]

I have read RME’s laptop optimization suggestions but they seem to be specific to Win98 and 2K. Any XP optimization instructions?
http://www.musicxp.net/

Also, how have you got the RME's clock set up? Is it set to Autosync? I would try using a word clock cable between the Digiface and Behringer with the Digiface as the master. That's how I do my Multiface and I never have any popping/clicking issues.

[Bob L]

In my current 35 track recording setup at the Goldun Nugget, spread across two machines running in Master/Slave combination, I have had no clocking issues, once I paid close attention to the setup.

If you can, you might try setting the RME card driver to MASTER. Then set the converters to slave direct from the optical pipes plugged into them. The exact settings will be labeled differently on different gear.

On my Behringer ADA8000 they are labeld as ADAT... the other choices are master 44 and master 48, or wordclock... I leave them to look at the optical.

Between my two machine RME digiface boxes, I take a WordClock cable from the first one (on the Master machine) and connect to the WC in on the second... that slave computer has the RME driver set to autosync, with WC In as the prefferred choice. This has worked flawlessly for the so far collected 4 hours of audio recording.

My guess is that you are having a clocking issue... In your setup, it doesn't sound like you should need to use WC at all... simply set the RME card to be master and let the other converter devices chase the optical... not looking for WC.

Bob L

[Carey Langille]

I used to get occasional Glitches using just my lighpipe for sync, with RME being the master, but now i use RME as WC out and the 3 ada8000's set to WC i have Never had another glitch... Hmmm.... Works for me... :)

[Leadfoot]

I used to get occasional Glitches using just my lighpipe for sync, with RME being the master, but now i use RME as WC out and the 3 ada8000's set to WC i have Never had another glitch... Hmmm.... Works for me... :)


That's cool, thanks for the heads up. Maybe the adat lightpipe is just trying to do too much at the same time. I don't know, but I'm gonna try your setup with the wordclock stuff, see what happens. Then the light pipe can just handle the audio.. if I'm guessing correctly.
Thanks,
Tony

[Ed Snape]

Thanks everyone. At least 3 different sync setups have been proposed.

Currently in my problematic system, the Digiface, set as master, w/c out feeds a coax T which feeds directly into the ADA8000, and thru short coax cable to the OctaMic. ADA8000 is set to slave to w/c in, and Octamic is set to slave to w/c in, 44.1, and its w/c-in jack is terminated. Monitors are fed by output channels 7 & 8 in the ADA8000 which is seen as ADAT #2 I/O by the Digiface.

I will try Bob's suggestion first."setting the RME card driver to MASTER. Then set the converters to slave direct from the optical pipes plugged into them. ...In your setup, it doesn't sound like you should need to use WC at all... simply set the RME card to be master and let the other converter devices chase the optical... not looking for WC."

Another problem is that I can't get the present setup to misbehave here in the studio, only at the concert hall, but I should be able to test the new alternate setup for several hours during rehearsal at the hall.

[Craig Allen]

Another problem is that I can't get the present setup to misbehave here in the studio, only at the concert hall, but I should be able to test the new alternate setup for several hours during rehearsal at the hall.

This type of behavior awalys makes me suspicious. Have you considered that the problem may be a power related issue? Are you running any power conditioning in your remote setup? Just a thought.

[AudioAstronomer]

ACtually Ive had similiar problems when using UPS's to supply power to wordclocks (or similiar) could be similiar...

[Bob L]

WordClock can be finicky... that's why I would try the ADAT light-pipe slave idea first.

Bob L

[Ed Snape]

In reply to Buck's question about power: Currently the only power treatment is a surge suppressor plug strip in the portable rack. It is plugged into house technical power, orange recepticles with home run grounds. There have been some posts in the RME forum about staticky computer noises being caused by ground loops. Some have suggested ground lifting the computer power supply cord. Instead, I have run #10 copper from the Digiface to plugstrip ground. In earlier tests, this hard ground greatly reduced computer hash.

In the studio, all equipment but the monitor amp and printers is on UPS.

What do you suggest?

Ed

[Craig Allen]

It's just a thought, but if there was some sort of issue with power - a voltage drop or something, then the laptop would still run fine on battery power, but everything else would drop out for the duration of the voltage drop (if it was a significant enough drop) and would cause an audible glitch. If it's quick enough, the lights wouldn't even dim. This could happen if a large inductive load started up (HVAC system), but usually the duration of a voltage drop when something like that happens is a few seconds, and would be noticed elsewhere. It's a long shot, but I thoght I'd mention it.

[Ed Snape]

I

My guess is that you are having a clocking issue... In your setup, it doesn't sound like you should need to use WC at all... simply set the RME card to be master and let the other converter devices chase the optical... not looking for WC.

Bob L

Hi Bob, Finally back in the studio and attempting to implement your suggestions. I now realize that RME OctaMic is only able to slave to WC as it has no ADAT ins to slave from?.

What do you think about letting the OctaMic be master generator, Digiface slave to ADAT in from Octamic, and ADA8000 slave to Digiface Adat out?

I will also verify the integrity of the BNC cables used for WC in the troublesome setup. Its hard to tell which position the OctaMic's 75 ohm load toggle is in, so I will verify that with an ohm meter.

Thank you.

[Bob L]

I've never used the OctaMic, but the steadyclock low jitter claim may make it a perfect choice for the master...

Give it a shot and let us know the results.

Bob L