Anyone else have issues with OmniMic and active USB extensions?

[curt_c]

Bill, first let me add my kudos for providing us with such an excellent product. I’m sure there was a lot of hard work in making it so dead simple to operate that even a graybeard like me can obtain meaningful results.

By necessity, I have my measurement computer located away from my normal testing location. I purchased a 10m active extension cable for this purpose but it exhibits a puzzling issue when utilized. The measured level intermittently increases by something like 70 dB, causing the warning on the OmniMic panel. The lowest level setting on the OmniMic panel will not resolve the issue, and the response appears to be reasonable other than peaking around 140 dB. Half the time it responds with normal levels. Switching to a shorter passive cable resolved the issue. I attribute this to a faulty amplifier in the cable, but surprisingly, the active cable seems to work fine when used for my wireless internet dongle on the same machine.

Is there any issue with using OmniMic with an active extender, or other then the normal USB 2.0 limitations, is there a length limitation on USB cables used with OmniMic? I read through the manual, but easily could have missed it.

Thanks again for a great product.

C

[bwaslo]

USB standards say to stay within 5m on passive cable length, though I've done ok with somewhat longer. An active cable would theoretically let you go longer, but it may depend on the cable. The thing about USB audio (unlike USB networking) is that the audio stream is continuous and can never be resent -- if the stream gets broken because anything on the path gets too busy to keep up, then that portion of data is just simply lost (and apparently in your system appears as a big noise spike when it happens).

OmniMic looks to the computer system just like any USB stereo microphone, uses the built-in Windows USB drivers even. An active extender is essentially another USB hub, something else the main computer has to now manage without losing bits. You might find that it will work smoother with the extender if you turn off all wireless and bluetooth hardware attached to the computer -- wireless/bluetooth can both be time resource hogs and may be keeping the main system from keeping up with messaging from the OmniMic and the active extender.

[Face]

I've had no issues using this cable: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=130-568&FTR=130-568

[curt_c]

You might find that it will work smoother with the extender if you turn off all wireless and bluetooth hardware attached to the computer -- wireless/bluetooth can both be time resource hogs and may be keeping the main system from keeping up with messaging from the OmniMic and the active extender.

Thanks Bill, Face,
As a matter of course, I always turn off the wireless network and the antivirus programs, but it’s been working fine with a shorter, passive cable. I think the most likely cause of the issue is a poor quality active extender.

One thing I really like about the response and distortion sweeps is it appears to average the last few sweeps to eliminate impulse noise. If this is the case, in general terms, (I'm not looking for proprietary information) what is algorithm used for the averaging?
-Just curious.

BTW, the HD routine is great, and so much faster than the stepped sine wave program I used previously. I’ll never go back…

C

[arlis_1957@yahoo.com]

I have used a three meter extention from time to time and have not had a problem. I agree, good system.

[exojam]

Curt,

So I see you are now using an Omni. I will be interesting in seeing how things go in your measurements with it.

James