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Re: decent portable mic pre with optical out

Subject: Re: decent portable mic pre with optical out
From: "Rob Danielson" danielson_rob
Date: Wed Nov 15, 2006 12:21 pm ((PST))
At 2:42 PM +0000 11/15/06, oryoki2000 wrote:
>The problems with the UA/5 are (1) its self-noise
>is relatively high when you need to crank up the
>pre-amp's volume, and (2) it's relatively heavy and
>bulky with an external 9V power source.
>If you need to use a preamp with a Hi-MD recorder, I'd
>suggest using one that provides analog line out rather
>than optical out.  The A/D circuit in the Hi-MD recorder
>works very well.

Astute. With 45dB, 53dB and 50dB of gain respectively for Oryoki's
list of ext pres, compared to 75dB for the internal Hi-MD mic pre
(and the same A/D as line), using any external pre -> line
analog/digital input for quality purposes might not prove effective.
Quite likely, one would elect to use the analog input to make up for
the lower pre gain if recording ambience in quiet locations.  I'm
basing this on Richard test of the Hi-MD's internal mic pre concluded
that the noise from Hi-MD mic pre is faintly audible when used with
mkh 40's mics with dB12B(A) self-noise and 25mV/Pa sensitivity. My
listening test suggested the Hi-MD mic pre is a little quieter, but
his test is a safe reference.  So, one would need very quiet and
sensitive mics hoping to improve on Hi-MD recordings using an eternal
pre. There would be A/D differences, but at this price range of
converters, they are very likely insignificant and probably not as
much of a factor as the 22-30 dB of gain that would be forfeited with
these external pres if the Hi-MD's digital input was used.

What I thought was "neat" is the possibility of tricking the UA-25 to
work in the field for only $160 more than a portable phantom power
supply and getting a computer interface too. It seems I can get
considerable above-unity gain using the Hi-MD analog line input at
record level "30"  though I've not measured it. Rob D.

>  Let me know if you'd like information
>about small preamps with analog output.
>Attached are specifications of the three models mentioned
>typical price...$325
># of channels...2
>A/D conversion...20/44.1
>input...XLR balanced
>output...SPDIF optical and coax
>max gain...45dB
>gain control...continuous, 0 dB to 45 dB
>noise rating...-125dB
>power source...9V battery
>battery life...8 to 10 hours
>battery access...external pocket, no screws
>indicator lights...none
>dimensions...3" x 5.75" x 1.25"
>weight...approx 16 oz
>Manufacturer...Core Sound
>typical price...$550
># of channels...2
>A/D conversion...24/96
>input...5 pin mini-XLR
>mic power...9V or 48V phantom power
>output...SPDIF coax and optical
>headphone jack...
>max gain...53 dB
>gain control...continuous, 13 to 53dB
>noise rating...-135 dB
>power source...9V battery
>battery life...5.5 hours with no mic power
>battery life...2 to 4 hours when supplying 48V phantom
>battery access...external pocket, no screws
>indicator lights...power, activity, clip
>dimensions...5-1/16" x 3" x 1-3/8"
>weight...278g  9.75 oz
>typical price...discontinued, available used
># of channels...2
>A/D conversion...24/96
>input...XLR, phono, SPDIF optical and coax
>mic power...48v
>output...USB, SPDIF optical and coax, RCA, phono
>headphone jack...yes
>max gain...50dB
>gain control...continuous
>noise rating...-95dBu
>power source...AC mains
>battery life...n/a
>indicator lights...peak, power
>battery access...external
>dimensions...218 x 137 x 47
>dimensions...8-5/8 x 5-7/16 x 1-7/8
>weight...0.7kg, 1 l lb 10 oz
>comment...Oade mods, battery power mods

Rob Danielson
Peck School of the Arts
University of Wisconsin-Milwaukee

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