Re: SimpleP48 -- Polarity
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I just checked my Pin 3 SimpleP48 against my U87 and more scientifically, looked at the waveform from an impulse. Both show that Pin 3 for the "+"of the capsule provides the signal swinging positive upon sound wave moving the diaphragm?in.? My thoughts here are that the polarity?of the electret film is such that its increase in voltage as the capacitance?goose?down results is opposite that of the bias voltage on the gate of the FET. I believe?Henry mentioned this.?
Jules
I'm a little confused, myself... all the SP48 mics I've ever made
have capsule + to XLR pin 3. A few years ago I went through all of
my microphones (commercial and DIY), and all of my devices and
preamps and 1/8" jacks and cameras and such, to confirm polarity
on everything... I do a lot of stereo recording, mid/side, etc, so
I needed to be sure, in order to avoid confusion and delays when
mixing.
The only things that tested "wrong" were some PiP inputs (e.g.
Zoom H4N PiP inputs are "inverted" polarity), an EV666 dynamic, my
dbx RTA-M measurement mic, the 12AX7 stages on a tube amp project,
and a few other minor things. All the SP48 mics tested as normal
(i.e. matched all the commercial mics), which if I'm understanding
this thread correctly should not be the case... ?
I just tested a SP48 mic again (against an AKG C-535-EB) and it
seemed to be of correct polarity.
Looking back through all my old project schematics, it's always
pin 3 to +... (with one exception, which is the RCA mod SP48, but
my understanding is that that circuit is supposed to be reversed
from normal.)
When testing polarity, I hold two mics right next to each other,
make a deep "p" pop sound, and in the DAW confirm that the
wavefront excursion for both mics is in the same direction.
Jules -- have you confirmed anything recently one way or the
other?
-Casey
On 12/17/23 05:52, Jules Ryckebusch
wrote:
Wow, lightbulb
moment?for me on this one. You are correct. Now my conundrum.
I have? multiple mics out there wired with "+" to Pin 3. It
works but the absolute phase is?obviously reversed.
Hmmmm....??
Jules
Think it over.
If capacitance increases, voltage goes down because C.V is
constant.
Le 17/12/2023 ¨¤ 03:51, Jules Ryckebusch a ¨¦crit?:
Hmmm. ¡°When
the air pressure rises, the capacitance increases, Vgs
& FET current goes down¡±?My understanding is
that when air pressure rise capacitance goes up and that
as the charge on the capacitor can not change
instantaneously the voltage goes up. ? Thus voltage across
the Drain and Source goes down as it conducts more.? Love
some insight on this here if I am looking at this
incorrectly.?
Best Regards,
Jules Ryckebusch?
When the air pressure rises, the
capacitance increases, Vgs & FET current goes
down,
--
Best
Regards,
Jules Ryckebusch
214 399 0931
-- Best Regards,
Jules Ryckebusch
214 399 0931
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