At 8:04 AM +0000 6/11/10, Raimund wrote:
>
>
>Eric Benjamin wrote:
>
>> Making the generous assumption that the Quadmic noise is -129 dBV,
>>it's 10 dB quieter than the microphone. That's good, but maybe not
>>good enough. If you rms those two noise sources together that gives
>>you a 2.4 dB increase in noise relative to the microphone with a
>>'perfect' preamplifier. OK, 2.4 dB isn't a substantial hit in
>>performance. But you pay a lot for those quiet microphones!
>
>Hmmmm... Here is something wrong! If the preamp noise voltage is 10
>dB lower than the noise voltage of the microphone, then one would
>get an overall increase of the noise floor by 0.4 dB only (see
><http://www.rane.com/note148.html>http://www.rane.com/note148.html
>or
><http://www.avisoft.com/tutorial_mic_recorder.htm>http://www.avisoft.com/t=
utorial_mic_recorder.htm).
>I guess that this slight increase is inaudible and therefore
>irrelevant.
>
>> I have enjoyed using the Earthworks ZDT1024 in the past, and it
>>has input noise of -143 dBV at a gain of 60 dB, 14 dB better than
>>the Quadmic. On the other hand, it's $3200 for four channels as
>>opposed to $550, and that's a huge price penalty.
>
>I'm afraid that a preamp noise figure of -143 dBV does not provide a
>significant advantage in conjunction with any real microphone under
>real-world conditions...
>
>Regards,
>Raimund
>
I'm sure the extra cushion gives Eric more confidence in lab tests,
but yes, if the Quadmic introduced additional noise with AT3032's or
NT1-A's (mics with 8 dB[A] and 6 dB[A] self-noise respectively,
several of us would have noticed it by now.
If I needed four channels of pre for surround work at this juncture,
the DR 680 would be tempting to me. There's no quality drop and one
rental fee for job calling for 6 channels would cover the cost
difference. A couple of more mics for insurance or to try something
different seems attractive to me. Rob D.
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