Phantom Power for Tandy/Realistic PZM mics
Anthony Sawford
Tandy/Realistic PZM mic to convert it to phantom power. Can anyone
enlighten me as to what it is, please?
--
Tony Sawford, PowerSolve Ltd | asaw...@cix.compulink.co.uk
Cambridge | to...@ratfink.demon.co.uk
UK | CompuServe 100044,2673
Alan Macaluso
Chris Christensen for an excellent 'how to'. I couldn't have done it better.
---------------------------------------------------------------------------------
THESE MODS ARE DONE AT YOUR OWN RISK; I WILL ASSUME NO LIABLITY FOR
YOUR ACTIONS.
With the low power consumption of the electret capsule of the RS PZM
you should only have to use a simple voltage divider to supply 12V,
or 9V or 6V or 1.5V to this capsule.
This modification requires skill in tracing out wiring both flexiable
and printed. It also requires the correct use of a soldering iron.
The parts for this modification are: 3-10K ohm metal film resistors,
1-15uF 35 Vdc capacitor and a Male XLR connector.
THESE MODS ARE DONE AT YOUR OWN RISK, I WILL ASSUME NO LIABLITY FOR
YOUR ACTIONS.
The RS PZM used to have a transformer in the battery box. This
transformer works fine in suppling a balanced output from the PZM's.
And is desired for this mod.
First of all cut off the 1/4" plug and wire in a XLR, the shield goes
to pin 1 the red wire to pin 2 and the black wire to pin 3.
Open up the battery box and throw away the battery. Trace out the
wiring and locate the series supply resistor that goes to the capsule,
it will be coming from the + battery terminal. Lift the end of the
battery that went to the battery.
Find the ends of the red and black wire that come into the battery box
from the XLR connector that you put on.
Connect a 10K ohm resistor to the PC board where the red wire
connects. Connect another 10K resistor to the place where the black
wire connects. Connect the free ends of these resistors together.
You should be able to connect the XLR to the mixer and with the phantom
power on you should be able to measure 24Vdc between the junction of
these 10K resistors and the shield of the cable (the mic won't work yet).
Connect another 10K resistor between the junction of the other 10K's
and the shield wire. With the XLR connected and the phantom power on
you should measure less than 24 Vdc and probably very close to 12 Vdc.
This 12 Vdc source can be connected to the capsule series supply
resistor that you found eariler. You may wish to put an polarised cap
across the last 10K resistor you installed as a filter cap.
THESE MODS ARE DONE AT YOUR OWN RISK, I WILL ASSUME NO LIABLITY FOR
YOUR.
THESE MODS ARE DONE AT YOUR OWN RISK, I WILL ASSUME NO LIABLITY FOR
YOUR.
Am I clear?
--
Chris Christensen The opinions I express are my own,
chr...@gold.gvg.tek.com and sometimes they are wrong!
916-478-3419 FAX 916-478-3887 After all, I AM only human.
Chris Christensen
>Got this mod off the net. I've used it succesfully for years. Thanks to
>Chris Christensen for an excellent 'how to'. I couldn't have done it better.
I sat here and read this posting intently. I had skipped over the header so
I didn't see the note above...... So anyway I am reading this posting,
saying to myself "hey this one looks like it'll work? Then I get to the end
and saw my .signature.... :-)
So it really works! I haven't tried it.... I got a box of those damn PZMs
in the warehouse, I guess I gotta try it myself!.
Here is an idea for someone who has the time and tools.
You should be able to modify a Switchcraft mic connector to mount up to the
plate of the mic. You put the transformer, resistors and caps inside the
shell* and there you have it!
* you need to drill or machine out the strain relief bosses inside the
connector housing. Then you need to cut the shell lengthwise on the end of
the connector to provide a flat place to mount the shell. A coupla small
mounting holes drilled and tapped to attach the shel to the plate and you
will have a durable connection point.
--
D.R. "Chris" Christensen Grass Valley Group (the day job)
chr...@fuggles.gvg.tek.com P.O. Box 1114 mail Stop N32B
916-478-3419 FAX 916-478-3887 Grass Valley, CA 95945
Neither I nor my employer is responsible for anything I say or do.
C.M. Hicks
Christopher
======================================
HOW TO PHANTOM POWER A RADIO SHACK PZM
======================================
Introduction
============
This article describes two ways of powering electret capsules (with
built-in FET), such as that used in the Radio Shack PZM, with phantom
power. The first method is the simpler; the second is more complex,
but provides a lower output impedance, thereby allowing longer lines
to be driven.
Both remove the horrible transformer, and both remove the equally
horrible electrolytic capacitor from the original RS circuit.
Method 1
========
10u
+---------o-------------||------o----------------- HOT (2)
| | |
| |- |
| CAPSULE 22k
| |+ |
| | 10u |
| o-------------||------|------o---------- COLD (3)
2k2 | | |
| 2k2 | 22k
| | | |
| +---------o----o------o------+
| +| |+
| 12V 10u
| -| |-
--o-------------------o----o------------------------ GROUND (1)
Notes:
1) The component "12V" is a 12 Volt zener diode
2) The 10u capacitors in the HOT and COLD signal leads should be
high-quality plastic film types. The values of these may be
reduced to 2u2 if the preamp input impedance is 10k or greater.
3) The 10u capacitor in parallel with the zener should be a tantalum
type, and can have a 10n plastic film cap in parallel if you wish.
4) The cable to the capsule should be twin+shield. The shield should
be connected to ground near the zener diode, and left unconnected
at the capsule.
5) The polarity of the capsule is important. The + side is the one
connected to the casing. (Odd but true, at least in the case of
the RS PZM.)
6) The pinout given is the standard for XLR3 mic connectors.
7) If you want to use the existing RS box you will find that the 10u
capacitors do not fit. If you *must* then use electrolytics for
these (>50V working) and bypass them with 100n plastic film caps.
Method 2
========
+---------------------------------+
| |
2k2 +---22k----+ |
| | | |
| | E--o---|--------------- COLD
o---------||----o--o-------B |
| 1u0 | C |
|+ +-100k-+ | |
CAPSULE |---o------o
|- +-100k-+ | |
| | C |
o---------||----o--o-------B |
| 1u0 | E--o---|--------------- HOT
| | | |
| +---22k----+ |
| o----+
2k2 +| |+
| 12V 10u
| -| |-
+---------------------------------o----o---------- GROUND
Notes:
1) Notes 1, 3, 4, 5, 6 from above apply here too.
2) Component EBC is a PNP bipolar transistor, eg BC479
3) The 1u0 capacitors should be high quality plastic film types
4) Noise floor *may* be lowered by filtering the 12V supply for
the capsule with a series R parallel C arrangement.
5) This circuit will fit in the existing RS box, but a metal one
is recommended for the additional screening it affords.
THE END
=======
--
=====================================================
Christopher Hicks http://www.eng.cam.ac.uk/~cmh
c...@eng.cam.ac.uk Voice: (+44) 223 332767
=====================================================
Chris Christensen
>In article <31tiur$7...@cmcl2.NYU.EDU> a...@cns.nyu.edu writes:
>>Got this mod off the net. I've used it succesfully for years. Thanks to
>>Chris Christensen for an excellent 'how to'. I couldn't have done it better.
BTW....... the mod posted was for a 24 vdc phantom supply. You will need to
alter the resistor ratio to divide a 48 volt supply down to something useful
to the RS-PZM's.
Increase the value of the pair of 10k resistors that are connected to the
red and black wires.....
Technically Sweet
mike stuck behind a junky transformer. I've built the original
Phil Rastocny mods for unbalanced operation and they sound fine,
except they don't feed my DAT mic inputs. So, try the Christopher
Hicks ones first if you want to use the PZMs with a mixer.
Getting rid of the xformer adds ~10dB to the dynamic range of
the mic. It was pretty startling.
--
Lance Norskog
thi...@netcom.com
Artisputtingtogether. Art s th ow n aw y.
C.M. Hicks
>The whole point of chopping up the RS PZM is that it's a decent
>mike stuck behind a junky transformer. I've built the original
Hold on... It isn't *that* good a microphone. Its main endearing
feature is its price, and in this world you get what you pay for,
and the RS PZM is no exception. Yes, it is good for the money, but
that is all. Yes, the transformer is ghastly and should be exorcised
as rapidly as possible.
>except they don't feed my DAT mic inputs. So, try the Christopher
>Hicks ones first if you want to use the PZMs with a mixer.
If I find a dull moment over the next couple of weeks I may just
design a little PCB for a truly-balanced phantom-powered line driver
for electret mics such as the RS PZM. Don't hold your breath though.
Christopher
David Cutts
>If I find a dull moment over the next couple of weeks I may just
>design a little PCB for a truly-balanced phantom-powered line driver
>for electret mics such as the RS PZM. Don't hold your breath though.
>
Well, speaking as one who knows nothing about electronics (perhaps I
shouldn't admit that in a "pro" newsgroup) but can make up a PCB and
wield a soldering iron, I'll be eternally grateful if you do make the
time. I read your circuit descriptions re the RS PZM but I've no idea
how to turn circuit diagram into functioning article.
David.
woahder...@gmail.com
This post was made a few days before i was born O_o