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Old February 20th, 2005, 12:26 PM   #1
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Help connecting mixer to AD converter

I just bought a SoundDevices 302 mixer (Yeah!) and want to make sure that I'm connecting it correctly. The AD converter has two balanced mic level inputs. I called the manufacturer and asked how much attenuation I would need to connect it to a pro line level mixer and they said -20db. That makes no sense to me, but I figure they know their equipment better than I do. The 302 has software adjustable attenuators that go from -2 db to -16 db, and then from -40 db to -56db. The manual also says that the default line level output is 0, instead of +4 dbu like most other professional mixers. My question: since the mixer output is 4 db lower than other mixers, is -16 db enough attenuation, since 4 plus 16 equals 20? I had hoped that I wouldn't have to deal with external attenuators anymore.

Here are the specs for the AD converter -- http://www.micsupply.com/ad20.htm

And for the 302 -- http://www.sounddevices.com/products/302master.htm
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Old February 20th, 2005, 12:37 PM   #2
 
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That SHOULD work, but I'm confused about why they're not following the +4 or -10 standard.

Regarding the converter, keep in mind that -20dB in the digital realm is equal to 0dB in the analog realm based on the ATSC spec. You'll find various manufacturers have played with that spec over the years, but the standard is -20dBFS equals 0dBFS, so it may be, and likely is, that the converter is basing on FS rather than VU.
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Old February 20th, 2005, 01:27 PM   #3
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Wow that was fast. Thanks Douglas. There does seem to be a way to set the VU reference to +4 or +8, assuming I understand all this correctly.

From the manual:
NOTE: Unlike other analog mixers, the 302 is caalibrated with 0 VU reference at 0 dBu, not +4 dBu. If you primarily interconnect with analog video cameras, set the 0 VU reference to +4 dBu by making the change in the Setup Menu. The 302's scale is designed for digital recording devices, providing maximum information between -30 dBu to 0 dBu where typical peaks occur (-50 to -20 dBFS).
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