K3/K2 - Microphone Question

Just came into possession of an ElectroVoice PL91 microphone.  The specs says it has 150 ohm impedance.  I think that the K3 would like to have 600 ohms.  I would imagine that this could be used on the K3 if you used an impedance transformer.  Comments?

Lee - K0Wa


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[Jim Brown-10]

On Sun, 26 Jul 2009 21:51:23 -0700 (PDT), Lee Buller wrote:

>Just came into possession of an ElectroVoice PL91 microphone.  The
specs says it has 150 ohm impedance.  I think that the K3 would like
to have 600 ohms.  I would imagine that this could be used on the K3
if you used an impedance transformer.  Comments?

NO TRANSFORMER REQUIRED. The K3 designers do not understand audio.
It will work just fine. Just wire it properly, following the diagram
in

http://audiosystemsgroup.com/HamInterfacing.pdf

The only shortcoming of this mic is proximity effect -- extreme bass
boost when it is very close to the sound source. To correct for
that, you will want to tweak the TXEQ on the K3 to roll off the
bottom three bands to their maximum, and boost the top two EQ bands.  

73,

Jim K9YC


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[George & Jan]

Lee,
In broadcast & pro-audio (probably other services) - microphones aren't
impedance matched. Normally you want to have the microphone load impedance
(amplifier mic input) at least 10 times the microphone's characteristic
impedance. My K3 schematic shows a 10k input pad-out resistor to a 100k
feedback resistor so the 600 ohm microphone should have no issues.
George - AI4VZ

Just came into possession of an ElectroVoice PL91 microphone.  The specs
says it has 150 ohm impedance.  I think that the K3 would like to have 600
ohms.  I would imagine that this could be used on the K3 if you used an
impedance transformer.  Comments?

Lee - K0Wa

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Please help support this email list: http://www.qsl.net/donate.html