Strange fix for pops in USB audio output

[MizeSoundGuy]

I have used SCS for several years now at several theatres and with lots of different computers and many kinds of output devices (either headphone outputs or low-end USB however). My main output box has always been a Tapco/Mackie Link.USB 2x2 device and it has never given me problems before. For a production of Shakespeare in Hollywood I just put up, I put off buying a new output device because the old one worked fine with a re-purposed Dell M65. Until last night (opening night, no less) when we started getting sharp pops in the FoH channels driven by the Link.USB. We somehow limped through the night rerouting all the audio through the headphone output that was supposed to be used for two hidden upstage speakers. An additional problem was that the audio from the opening video routes only to the Default Output and I could not (until I read another post on this forum) figure out what I had done wrong because it worked properly through all the rehearsals (Windows 7 change the Default Output while I wasn't looking). We opened the house 20 minutes late and believe you me, the Eyes of Texas Were Upon Me because of it.

I brought the computer home after the show and spent all day trying different things. I bought two different USB audio devices locally and both of them had even worse pops than my device. I tried tinkering with buffer sizes, measuring latency (http://www.thesycon.de/deu/latency_check.shtml), different USB ports, disabling everything that I could think of -- nothing worked.

I came across one posting in a computer audio forum (can't remember which one) that I discounted at first but when things got desperate, I tried it: Connect the USB audio device to the computer through a USB hub. I tried it and it worked. No popping, no clicking. Strange.

What do we learn from this?
1) Never put 32-bit Windows 7 on a laptop with no Windows 7 drivers (I ran great until opening night -- what changed? I have no idea) -- the M65 has no Win7 drivers for it.
2) In the show notes for the board operator, remind them to go to Sound in the control panel and make sure that the Default Output is the one you want it to be -- Win7 will change these things randomly and for no apparent reason.
3) Once you settle on a USB port for your output device on your computer, stick with it. This may be superstition but I think Win7 changes settings just to mess with you .

I'm still going to replace my Link.USB (it's USB 1.1 for goodness sake) with a Behringer FCA610 but I will either get proper Win7-capable computer or re-image the existing one with WinXP.

Live and Learn.

--Jeff
Mainstage Irving-Las Colinas

[Mike Daniell]

Interesting notes, Jeff. The Dell M65 looks like a good machine, even for Windows 7, so I'm puzzled as to why you would get pops in audio, unless there's a problem with the performance of the USB port. But having said that, I'm confident you'll get better performance from a new Windows 7/8 machine, assuming it's well configured for audio and video.

Is the SCS Audio Driver set to DirectSound or ASIO?

Make sure your PC is optimized for audio - particularly that processor scheduling is set to "Background services". To do this:
- In control panel select "system"
- Go to "Advanced system settings" and then the "Performance" tab
- Set processor scheduling as "Background Services"
- Click "Apply" then "OK"

I agree that sticking to the same USB port is best. I've found that a USB device I've been using for ages comes up with 'initializing device' if I plug it into a different USB port, so Windows does seem to keep a record of what ports you use for each device.

[MizeSoundGuy]

Mike, thanks for the quick reply. No doubt, the M65 is a nifty machine but Dell has not published ANY Windows 7 drivers for it because it's an obsolete machine. For that reason, I suspect there is an issue with the USB ports. I tried all of them and they all glitched. Adding the unpowered USB 2.0 hub fixed it. Go figure.

The system is already adjusted for Background services and all the visual effects are turned off.
I am using DirectSound (using BASS) because I do not have an ASIO driver. If you can point me to a good one, I'll try it.
I will be trying a different computer shortly to see if there is a difference. One that was "Designed for Windows 7".

Cheers,

--Jeff
MainStage Irving-Las Colinas

[Mike Daniell]

I am using DirectSound (using BASS) because I do not have an ASIO driver. If you can point me to a good one, I'll try it.

The only ASIO drivers I recommend are those that are supplied by respective audio interface manufacturers. For example, I use a Roland Octa-Capture which comes with an ASIO driver (as well as a DirectSound driver).

I do not recommend ASIO4ALL or any similar utility. I had poor results when I tried ASIO4ALL sometime ago.

[MizeSoundGuy]

The Link.USB comes with an ASIO driver but it's old, for XP and when I use it, I cannot use the laptop headphone output.
Time to replace the box with something more modern I think. Or reformat the laptop as XP (and never connect it to a network).

Cheers,

--Jeff