Unbalanced mic wiring question for the tech heads!

[Martin]

hi folks, I've been given an awesome little 60's era national microphone, consumer level i assume but really nice all the same.

it came with a 6.5mm jack on the end, but i'd like to use an XLR connector on the end and stick it in the studio onto the box on the wall.




when i pull apart the jack plug, should i solder the core wire to pin 2 of the XLR and the shield to.....? 2? 3? both?

is there a tricky way i can balance the output of this thing to reduce noise even more?

[chris p]

XLR is pin 1 ground, pin 2 signal +, pin 3 signal -

At the very least, connecting the + to pin 2 and the - to pin 3 will get a signal out there. Most would say to connect pin 3 to the - as well, but if you can, connect it instead to the mic body.

You can get mic balancing transformers or there are other circuits that do the job without transformers (though most require phantom power).

The other approach is to keep the cool outer body, and rip apart an SM57 to replace the guts of the thing. That gives a good all-purpose (balanced) dynamic that keeps those cheeky grills.

[Martin]

thanks chris! the 57 idea could work! i'll see how i go with the wiring you suggested, already tried using pins 1 and 2, but i'll swap 1 for 3 and try again..

its useable but a little bit of noise..

if i can get my hands on a balanced mic i might change them over!

[rob]

you'll definitely need to put the hot onto pin2 and the shield onto pin3. Then you'll probably find to minimise hum you'll need to join pins 1 and 3 together. This could be a high impedance mic and if so will be unhappy talking to a normal mic pre. Sometimes with these old mics if you rip it apart you can find a way to separate the wiring from the capsule from the body and then are able to replace the cable with a twin core and wire it all up balanced with the body connected to pin 1 for grounding the body

[Martin]

thanks rob, it seems relatively happy talking to the mic pre's that we have...

it says the impedance written on it, i'll check it at work tomorrow to be sure

if i can figure out how to open the thing i'll take alook around!

[mfdu]

i have some dinky old unbalanced units that i DI

dynamic range of a puddle, built for a battery powered reel to reel

but they beat a 57 hands down, in the right situation

just a thought

chris
mfdu

[jkhuri44]

dynamic range of a puddle

ill b using that line from now on :P

[chris p]

There's a good idea, Chris MDFU

The DI Joe project (under the DIY heading) would cost less than an SM57 and still deliver a good balanced signal to the preamp.

[mfdu]

good good - all i'm saying is that an sm57 is not the only mic i want. . . and i certainly wouldn't want to pull apart something that sounds unique, only to shove the guts of a 57 in.


chris
mfdu