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Mystery feedback?

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Rich Swartzwelder
Mystery feedback?
on May 10, 2013 at 2:43:31 pm

Hello,

I've noticed a high-pitched noise in our system lately and I was hoping someone could help me discover the source. We have a mic running to a Mackie CR 1604. Audio from the board goes to a Behringer UCA202 which is connected to a MacPro. Audio is recorded with Soundtrack Pro. Everything sounds great until I arm a track for recording in Soundtrack Pro. Then the high-pitched noise appears. Feedback? I'm not an engineer by any stretch, so I'm a bit over my head here and any help would be greatly appreciated. Thanks.


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Richard Crowley
Re: Mystery feedback?
on May 10, 2013 at 7:21:17 pm

The high-pitch noise appears WHERE? WHEN?
Where are you hearing this? In headphones? In speakers? In the same room with the open microphone?
When are you hearing this? While recording (or setting up for recording)? Only when playing back the recorded clip?

Does disconnecting the audio inputs from the UCA202 make the noise disappear?
Does disconnecting the UCA202 from the computer make the noise go away?


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Rich Swartzwelder
Re: Mystery feedback?
on May 10, 2013 at 7:29:36 pm

Thanks for the reply. The noise is heard in whatever I'm using to monitor the recording (speakers or headphones). It is heard during the recording and is in the recorded clip. Like I said, the noise appears when I "arm" a track for recording in Soundtrack Pro. I tried Audition and get the same noise as soon as I arm a track. When I disconnect the audio inputs from the UCA202 the audio from the booth cuts out (of course) but the noise remains. Disconnecting the UCA202 makes the noise go away.


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Richard Crowley
Re: Mystery feedback?
on May 10, 2013 at 9:48:40 pm

"When I disconnect the audio inputs from the UCA202 the ... noise remains. Disconnecting the UCA202 makes the noise go away."

That would appear to implicate your UCA202, wouldn't it?


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Rich Swartzwelder
Re: Mystery feedback?
on May 10, 2013 at 11:40:23 pm

It would. I'm just wondering why the noise only occurs when the track is in record mode? When I listen to the audio through the headphone jack on the 202, it's clean.


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Richard Crowley
Re: Mystery feedback?
on May 11, 2013 at 1:51:36 pm

Without a sample to listen to, we are really just guessing. You may need someone to help you who is familiar with Mac hardware and software.


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Peter Groom
Re: Mystery feedback?
on May 11, 2013 at 9:04:00 pm

Where is the audio to hear
Peter

Post Production Dubbing Mixer


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Ty Ford
Re: Mystery feedback?
on May 12, 2013 at 2:31:10 pm

Hello Rich and welcome to the Cow Audio Forum.

Hate to say it, but Behringer doesn't have a sterling reputation for gear. I normally don't even bother to read about their products due to the rip off of the Mackie mixer some years ago.

After reading your post, I googled UCR202 and whine. Among many posts the ones below should give you a real warm and fuzzy that you are not alone.

http://forum.cockos.com/archive/index.php/t-51568.html

http://forum.audacityteam.org/viewtopic.php?f=27&t=69080

So, it appears that it's not feedback at all, but caused or generated by the UCA202. You can't expect too much from a $29 converter I/O box. If you're not doing professional work, it doesn't matter as much.

If you are doing professional work, you can't afford to "buy cheap." A real I/O box like the Sound Devices USBPre2 costs many times that of a UCA202 but is engineered and built properly. See here:

http://www.bhphotovideo.com/c/product/734341-REG/Sound_Devices_USBPRE_2_USB...

It's not the only USB I/O out there, but it's solid and you won't have to make excuses for it.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Richard Crowley
Re: Mystery feedback?
on May 12, 2013 at 3:26:49 pm

I have a UCA202 and I have not encountered any such behavior. It may be possible that you have a bad unit, but that could happen with any brand. I don't share others' low opinion of Behringer. We don't all drive Lamborghinis or use Sound Devices or Nagra, etc.


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Ty Ford
Re: Mystery feedback?
on May 12, 2013 at 3:50:43 pm

Richard,

I don't think I'v ever seen you hyperbolize! What fun!

I see Sound Devices gear as Ford, GM, Cadillac, not made of unobtanium or youcantaffordium. :)

I have never owned a Nagra. Given the amount of time you've been collecting and using gear, I daresay, much of it is well above Behringer quality.

That your device seems to work properly is a good thing. That many others have made similar complaints about this device and the whine tells us you got lucky. At best, perhaps computer systems are all so subtly different that Behringer's R&D money was exhausted well before they went to market with this device.

Bottom line. Noisy interface with evidence pointing to a compliance issue.

Perhaps you would favor us with an outline of your bits and pieces and settings to see if that would resolve Rich's problem and be of continued aid to anyone else who landed here with the same complaint. Are you running Mac or PC?

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Richard Crowley
Re: Mystery feedback?
on May 12, 2013 at 4:20:47 pm

I use only PCs which is why I suggested that someone with Mac experience would be of better help. I must say that my strong suspicion is that this is an operational (or configuration) problem, and not a hardware problem.

It would be good to know whether the "Monitor On-Off" switch position has any effect on the symptoms. And a comprehensive description of the setup and operation would be necessary for any significant assistance.


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Richard Neill
Re: Mystery feedback?
on Sep 5, 2014 at 12:28:13 am

I've used several of these devices, and usually the result is perfect, while on the most recent amplifier I've tried (which happens to be a 30-year-old design), I hear the whine. When I looked at the output with a scope, (while playing a wav file of silence), I see a large amount of noise: about 200mV pk-pk at 180 kHz or so! I think that the idea here is noise-shaping (the DAC moves all the noise out of band), though I'd have expected the amplitude to be much lower.

Anyway, my *guess* is that when such a signal is fed into most amplifiers, the input is band-limited, and the RF is cut off entirely, resulting in excellent audio. However, some amplifiers don't have a low-pass RC filter at the input, and the RF goes into some kind of diode junction (anything non-linear), which will cause mixing/aliasing of the RF down to ~ 1kHz, resulting in the observed whine.

I'm going to experiment with a simple RC filter on the phonos to see if it helps.


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