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Re: impedance matching

Subject: Re: impedance matching
From: "Rob Danielson" danielson_rob
Date: Fri Jun 16, 2006 2:44 pm (PDT)
Thanks for the rundown on your experiences and the radio shack number, Vick=
y.

I've done one test with A96F "stock."  It produced +3.9dB gain (from
nt1a->art phantom->NH900 to nt1a->art phantom->A96F-> NH900 Maximum
gain). I do detect some noticeable changes in tonal quality and
perhaps noise difference too. I'll  change the A96F to the "150 ohm"
setting, run more tests, then do a report with sonograms. Rob D.


Rob D.

At 7:07 AM +1000 6/17/06, vicki powys wrote:
>Re impedence matching, for what it's worth I've successfully used a Tandy
>impedance adapter with a Sennheiser ME67 mic going into a Sony Walkman WMD=
6C
>cassette recorder, (the recorder is ancient but I carry it on longer trips
>as a backup for DAT).  The sound to the walkman is definitely louder using
>the adapter, and it also serves to connect XLR mic to the mini-plug walkma=
n.
>The impedance adapter brand was 'Archer' "Lo-Z balanced to Hi-Z unbalanced=
"
>274-016.  Maybe they don't make them any more, but they were relatively
>inexpensive.  The transformer had female XLR to quarter inch pin so I need=
ed
>to get an inline RCA adapter, then made up a lead RCA to minijack.  Works
>with stereo too, using 2 adapters.  The cassette recordings were definitel=
y
>better when using the impedance adapter, maybe 6-10 db gain.
>
>Vicki Powys
>Australia
>
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>on 10/6/06 3:54 PM, oryoki2000 at  wrote:
>
>>  I have read conflicting points of view about impedance matching:
>>
>>  1. Matching the impedance of the mic output to that of the recorder
>>  input reduces the power lost when a signal is transmitted.  The result
>>  is a louder recording without needing to boost the signal through the
>>  recorder's preamp.  For a brief discussion, see:
>>
>>  http://hyperphysics.phy-astr.gsu.edu/hbase/audio/imped.html#c4
>>
>>  2. Modern transistor designs (meaning any audio device made since the
>>  1980's) use voltage transfer rather than power transfer.  Voltage
>>  transfer is actually improved when there is a large difference in
>>  impedance between mic and recorder.  So matching impedance will reduce
>>  the volume of a recording.
>>
>>  http://www.shure.com/ProAudio/Products/us_pro_ea_imepdance
>>
>>
>>  Perhaps these two points of view are not mutually exclusive.  I have
>>  little understanding of the physics and electrical engineering
>>  principles involved here.  In my limited experience, however, I find
>>  impedance matching to be a valuable way to gain some volume without
>>  adding extra preamp noise.
>>
>>  The impedance of my Sennheiser ME62 is 200 ohms.  The impedance of a
>>  Sony minidisc recorder is about 2000? 5000? ohms.  (If I remember
>>  correctly, Sharp minidiscs have a mic input with 10,000 ohm
>>  impedance.) When I use a Shure A96f impedance matching transformer
>>  ($40) to raise the ME62 output to 2500 ohms, the minidisc records a
>>  considerably louder signal.
>>
>>  A member of this list had similar results by employing the Hosa
>>  MIT-156 impedance transformer ($20).  This device is also calibrated
>>  for 600 ohm mic output and 2500 ohm recorder input.
>>
>>  Both cables have the added advantage of having an XLR female connector
>>  on the mic end, and a 3.5mm male connector on the recorder end.  So
>>  either cable will let me connect a pro mic to the minidisc recorder.
>>
>>  --oryoki
>>
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>>
>>  "Microphones are not ears,
>>  Loudspeakers are not birds,
>>  A listening room is not nature."
>>  Klas Strandberg
>>  Yahoo! Groups Links
>>
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>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>


--
Rob Danielson
Peck School of the Arts
University of Wisconsin-Milwaukee
http://www.uwm.edu/~type/audio-art-tech-gallery/





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