Hi Paul--
I don't have a rms multimeter or scope. These are the file saturations I g=
et:
Pink Noise- > NT2000 -> Mix Pre at Full Gain -> Balanced Line Out/In
@ Unity -> 744T =3D -3.3 dB RMS
Pink Noise- > NT2000 -> 744T at Full gain =3D -.66 dB RMS
I haven't heard from Emil yet about the DR680 gain setting he used. Rob D.
=3D =3D =3D
At 1:33 PM +1000 8/21/10, Paul Jacobson wrote:
>
>On 20/08/2010, at 5:29 PM, Rob Danielson wrote:
>
>> Hi Paul--
>>
>> I do understand that gain measurement isn't as easy as one might
>> suspect and that the manuf. supplied specs are often lacking
>> sufficient criteria. 50 dB max gain for the 7XX's sounds very low
>> based on comparisons with SD pres rated at 66dB and other pres I use
>> regularly rated at 60dB of gain. The SD7XX is hotter than both. It
>> would be good to get some reliable numbers, but it doesn't impact my
>> test outcomes.
>
>Hi Rob,
>
>Gain measurements just require the right test gear. Connect a signal
>source to the mic input, increase the level of the test signal until
>you just hit 0dBFS or clipping, then measure the level of the test
>signal with a true rms multimeter or an oscilloscope. The measured
>voltage of the test signal is converted to dBU, and this gives you
>the gain measurement.
>
>Both Raimund's measurements and the Sound Devices specs point to a
>similar maximum gain for the SD 7-Series, so it would seem that the
>discrepancy has it's roots in the comparative assessment, and the
>logical thing to do would be look for the source of this discrepancy.
>
>The MixPre has a "headline" maximum gain of 66dB but this only
>applies to the balanced line output connected to a balanced input.
>If connected line-out -> unbalanced this drops to 60dB gain, and
>connected via tape out maximum gain is 56dB. The SD 7-series has a
>line input which has a maximum gain of -6 to 18dB to -20dBFS, which
>means when referenced to 0dBFS the gain is -26dB to -2dB - so
>effectively provides attenuation only. If you have the MP-2 hooked
>up to a SD 7-series recorder at maximum gain on both devices you'd
>see a total of 64dB gain. If you set the gain on the SD recorder
>line input to 0dB you'll be attenuating the MixPre by 20dB,
>resulting in an overall gain of 44dB. At this setting the MixPre
>would appear to have about 4dB less gain than the SD744. Same
>principle applies to any preamp/mixer run via a line-in.
>
>cheers
>Paul
>
>
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