|
Grex > Hardware > #47: XLR connector to mic. cartridge. HELP! QUICK! | |
|
| Author |
Message |
klaus
|
|
XLR connector to mic. cartridge. HELP! QUICK!
| 
Mar 16 23:33 UTC 1993 |
Can someone tell me how XLR or A3M 3 pin, low-Z microphone connectors
should be wired to the mircophone? I have a low-z microphone cartridge
that I want to wire to such a connector. The two wire microphone cartridge
has one shield wire and one signal wire. The XLR connector has three
pins. How do I wire them together? Help! I need this information before
the weekend!
|
| 42 responses total. |
tsty
|
|
response 1 of 42:
|
Mar 18 19:55 UTC 1993 |
Yoour michroophone is a 2-conductor , lo-z mic, accoording to
yoour description. That's unusual, but not unheard of. Lo-z mics
are almost always 3-cnductoor,
But,
The xlr/a3m wiring key is as follows. Pin 1 is ground! Pin 2 is the
poxitive (or hot) lead foor the audio signal. Pin 3 is the cold (or
opposite-poliarity) lead foro the audioo signal.
Yuu are going to have to make some decisiions PAST just wiringhte
mic to the cable. The cord goes into a pre-amp (mixer/whatever) and
there are a multitutde of input configurations avaialble.
Hi-z 2-wire, Hi-z 3-wire, and Lo-z 3-wire. are the most common.
Btw, the 2-wire configurations are also named UN-balanced.
3-wire are TYPICALLY named BALanced, cause there are two audio-signal
wires and one groound. The balance is achieved by haveint pins 2 and 3
and equal ammount of voltage above the pin 1 ground connection.
Balanced connections don'T pick up nooise adn buzz from "other stuff."
UN-balanced connections +do+ pick up noise and buzz from "other stuff."
If you are lucky, this 2-wire mic woo'T cause you too many prooblems, but
there are TWO wiring configurations to use. (again presuming that
the preamp-mixer is a pin-2-hot input). If it's a pin-3-hot input, neither
of these wiring schemes will work, which is you only clue to having
a renegade mixer.
First scheme: mic shield wire soldered to pin 1, only. mic hot lead
soldered too pin 2, only. Ignore pin 3 - no attachment. Plug it in
and try it out.
Second scheme: mic shield wire soldered to pin 1 +and+ pin 3. mic
hot lead soldered to pin 2, only. Plug it in try it out.
If that doesn't wrk wither, then you have either a bad mic or a
renagage mixer. Can't do anything abut the mic - but the connections
can be changed: First, use shieldon pin 1 , leave pin 2 unatached
and connect the mic hot lead to pin 3, only.
plug it in a try it oout. If there are problems, use the second
scheme, and tie pins 1 and 2 together (sield/ground) and leave
the mic hot lead on pin 3.
If that also fails - you are simply SOL.
All of the above PRESSUMES that this mic is 2-wire lo-z.
good luck
|
klaus
|
|
response 2 of 42:
|
Mar 19 12:41 UTC 1993 |
Thanks tsty! Yea, I have since tried to figure out what was going on
and a hi-z to balanced line adapter in my Radio Shack catalog gave me
a clue. I figured from that that there was probably a transformer
involved. One with a center tap so as to achieve the balanced signal
you mentioned. I didn't know how to wire it though. I figured that
the center tap should go to the center pin, while the remaining two
signals, 180 degrees out of phayse with one another, to the remaining
two outside pins. I'm not sure about the pin No's. I will have to
look into that under the light you have shed. Thanks again.
|
tsty
|
|
response 3 of 42:
|
Mar 24 04:29 UTC 1993 |
The pin numbers on a XLR connector are MARKED on the facing of the
connector where the pins are, easiest to read on the female style.
mechanical key \
pin 2 . . pin 1
. pin 3
If you aare thinking abut a RAdio Shack transformer notice that
it is hi-z to lo-z, with the mic connected tothe hi-z end, but yur
mic is a lo-z mic. Wrong connections! Might get some "sound" through
but you'lll be fortunate if it sounds very good (not impossible, just
fortunate).
And if you have to "wire" the Radio Shack adapter, things get into
mathematical combinations WayFast. Bal to un-bal adapters (passive,
like many <not most>) require a transformer. And the wiring can get
very confusing. Here is the basic (only basic)
Bal side un bal side
_____ ______
) || (
) || (
center tap/gnd ----) || (
) || (
______) || (_______ ground
The unlabled connections (not labled ground) are for audio the 2-wire
on the right side and the 3-wire on the left. please note that NOTHING
is herein mentioned about the "z" level of either winding. Either
winding can be hi-z, either winding can be lo-z, the windings can
be the same "z" or different "z's."
*Typically* the 2-wire side is hi-z and the 3-wire is lo-z. But no
guraantees. *If* this is what you get, notice that you'll be connecting
a your lo-z, 2-wire mic to a hi-z, 2-wire transformer winding, with
the lo-z,3-wire winding going tothe cable and then to the mixer/whatever.
That is NOT NECESSARILY better than connnecting without the transformer,
but you'll proabably get _some_ "sound" through anyway.
|
klaus
|
|
response 4 of 42:
|
Mar 24 13:17 UTC 1993 |
I got to this item too late but figured it out any way. The information
you gave me on wich pin did what was correct. We used it this last weekend
and it all worked great! Murphy, where were you?
In all honesty I was not wiring a microphone to the motel's PA system, but
and inductive "loop". Think of it as wiring a telephone pickup coil to a
PA system. (The thing with a suction cup used to record phone conversations)
In this case it was a conferance for hearing impared people, many of whome
have "tele-coils" built into their hearing aids, used in much the same way
as the telephone pickup. I had built a room loop (giant coil of wire hooked
to the output of a 100W PA amplifier.) so the speaker could "broadcast" over
this audio loop which could then be picked up those with telecoils on their
hearing aids. Odd concept, but it works quite well! Since I didn't want the
speaker holding 2 mikes (1 for the loop and the other for the motel's PA.
Not everone there was hearing impared.) I wanted to couple the one mike into
both systems. I didn't have access to the motel's PA, except for the mike
input jack, so I decided to use the loop's mike and some how couple it into
the motel's PA system. I didn't have much time to do it electronicaly
(make a splitter.) so I did the simplest thing I could think of. I wound
100 turns of #28 enamal wire in a 2" coil (z is about 8 ohms) and connected
that to a small 8 ohm to 1000 ohm audio transformer from Radio Shack. The
1000 ohm, center taped end was then connected to the XLR connector, just as
you mentioned above. By moving this little coil closer to the room loop. I
was able increase the coupling, thereby control the volume from the PA. It
was cheap, simple and worked great, though next time I'll take the time and
build a splitter.
|
danr
|
|
response 5 of 42:
|
Mar 24 16:53 UTC 1993 |
Interesting project. Sounds like there might be a (small) market for
portable loop antennas.
|
klaus
|
|
response 6 of 42:
|
Mar 25 12:05 UTC 1993 |
Yea, maybe some day. I have also designed and built a X-10 doorbell/phone
interface. Too much to do.
|
tsty
|
|
response 7 of 42:
|
Mar 25 15:30 UTC 1993 |
Great!
|
klaus
|
|
response 8 of 42:
|
Apr 1 14:45 UTC 1993 |
Oh, more April antics. Even the weather decided to chip in.
|
rcurl
|
|
response 9 of 42:
|
May 24 17:51 UTC 1996 |
An electret microphone question: I bought an electret lapel mike from
Alltronics. Its specs are: 3-9 VDC, 55-100 uA, output impedance ca 10K
ohms. However the plug on its cable is just 1/8" mono (two-wire). How do I
wire this (including battery polarity), and does it need an IC amplifier
for lower output impedance (and some gain)? I've inspected the electret
mike element from RS, and it is 3-wire - two the audio coax, and one for
the battery, and the diagram appears to show it includes an amplifier
(with an output impedance of 1K).
|
tsty
|
|
response 10 of 42:
|
May 24 18:23 UTC 1996 |
ummmm, just the element you bought? or the mic as an assembled unit?
what is the dbm output level? was there a batterybox included with
teh mic assembly? (apparently not, but i thought i'd ask anyway since
there is a 1/8 mini-jack apparently hardwired to the assembly.)
|
n8nxf
|
|
response 11 of 42:
|
May 24 20:22 UTC 1996 |
Two wire electrets are common. The power goes to the hot (audio) wire
through a ~10K resistor. Audio comes form the the same wire and is
isolated from the DC power source via a capacitor form .1 to 1 uF. The
negative side of the power supply and audio shield are connected to the
second wire on the element. It would be a good idea to check with the
manufacturer of the mic as to the recommended resistor value. You could
also put in a 10K resistor and measure the current (55 - 100 uA) for a
given voltage. Have fun! Electrets are neat!
|
scott
|
|
response 12 of 42:
|
May 24 21:40 UTC 1996 |
Interesting item! However, one note about balancing transformers: You almost
never do with with a center tap. The +/- pair just go into the windings of
the transformer. If you grounded the center tap then you can screw up phantom
power that might be present on the mixer.
(Phantom power is a 48 VDC microphone supply, between ground and the balanced
pair.)
|
rcurl
|
|
response 13 of 42:
|
May 25 20:34 UTC 1996 |
The unit is a mike (ca. 0.75"Lx0.5"D) with a lapel clip (and foam cover)
and a cable to the plug. No dB info is given. No battery box and no
identification. Wait! It came in a conductance-grid bag with the name
HONLYCO, and a sticker "Made in Taiwan" on it. KIaus, you are saying the
plug tip takes the (+) and the shield the (-), right? I think I'll start
at 1M and drop from there (with a 9 V supply). I want to use this for
input to a Powerbook. I don't know the input specs on a Powerbook, but it
works OK with a dynamic mike.
|
scott
|
|
response 14 of 42:
|
May 26 02:10 UTC 1996 |
Yes, Klaus was essentialy correct on how to use that type of mic. The power
is usually for a little preamp, since electret mikes have a permanent charge
on the element itself, but a little boost is needed. Probably similar specs
to a high impedance dyamic mic.
|
rcurl
|
|
response 15 of 42:
|
May 26 06:19 UTC 1996 |
The dynamic mike I have that works OK on the powerbook is a very cheap
Sony with 500 ohm impedance. RS's electret mikes indicate 1000 ohm
impedances. What is says in the Alltronics catalog is therefore a bit
puzzling, unless they really mean the needed resistor. I guess there is
nothing for it but to put the iron to the wire.
|
scott
|
|
response 16 of 42:
|
May 26 13:25 UTC 1996 |
I wouldn't consider your application to have a critical need for exact
impedance matching, Rane. Besides, a low impedance mic can plug into a high
impedance input just fine, as long as it can provide enough voltage swing.
Most buffered mics like electrets have low impedance and higher voltage
outputs. It's only dynamic or transformer balanced mics where you have a big
worry about a lower impedance input to allow current flow to contribute, and
you've already successfully tried a dynamic mic.
(Hint: What is the impedance of a wall output compared to the impedance of
a light bulb?)
|
rcurl
|
|
response 17 of 42:
|
May 26 22:19 UTC 1996 |
I understand the point. I am only concerned about trying to drive a low
impedance input from a high impedance mike. If the Powerbook input impedance
is 500 ohms, and the mike output impedance is 10,000 ohms, then there is
a problem.
|
scott
|
|
response 18 of 42:
|
May 26 23:08 UTC 1996 |
I'd be real suprised if the PowerBook had a 500 ohm input impedance. Just
doesn't make sense, unless it is Apple and they have an expensive mic to sell.
Still, active outputs usually do just fine even feeding low impedance
transformer inputs.
|
rcurl
|
|
response 19 of 42:
|
May 27 07:14 UTC 1996 |
A "PowerBook" *is* Apple, and they *do* have an expensive microphone to
sell (it says in the User's Manual - but I haven't seen them for sale
in catalogs, probably because people have discovered that any dynamic
(and maybe electret (!) microphone works fine anyway). [I better just
rig this thing up now, and report back how it works.]
|
scott
|
|
response 20 of 42:
|
May 27 13:34 UTC 1996 |
(Yes, I knew that the PowerBook is an Apple product... That was a joke about
Apple and standards. :)
|
n8nxf
|
|
response 21 of 42:
|
May 27 13:38 UTC 1996 |
Most sound cards, cassette players, etc. have 600 ohm input impedances. 600
ohm mics are common, common, common! Your electret should work just fine
Rane. I'll bet the tip on your mic plug is for power in (Through a ??K
resistor) and audio out (Through a .1 to 1 uF capacitor). The sleve on the
plug is than common for power and audio. Give it a go and see what happens.
BTW, 500 ohm impedance is plenty close enough to 600 ohm...
|
rcurl
|
|
response 22 of 42:
|
May 27 18:02 UTC 1996 |
With an input impedance of 600 ohms, I would need a 5 ufd coupling
capacitor for a half-power point at 50 Hz. Lo-and-behold, the RS electret
element has with it a circuit showing "3-10 ufd" cap being used, and I
just happen to have a 10 ufd rated at 35V....things are coming together
(now, where is that spare project box...). All this trouble, by the way,
is to tune my harpsichord with this Powerbook and LabMeter v2.0 - my tin
ear has always had trouble with equal temperment.
|
n8nxf
|
|
response 23 of 42:
|
May 28 13:52 UTC 1996 |
10uF than ;) The positive side goes to the electret end and the negative
side to the audio input. Many years ago, an engineer told me that Tantalum
capacitors were better than Electrolytic for audio coupling applications.
I don't remember why. (Perhaps it had to do with the memory effect displayed
by the dielectric they use.)
|
rcurl
|
|
response 24 of 42:
|
May 28 16:42 UTC 1996 |
Tantalums are "electrolytic" too. Now, here's another puzzle - my 10 ufd
cap is not marked (+) and (-), but rather has an arrow symbol pointing to
the "can" end (though the arrow has a sort-of dash in it....). Anway, I
presume the "can" is (-) - at least it was when I was a kid!
|