Unidyne III 545 - Broken or wrong cable?

[milet22]

After reading through posts here on mics, I decided to give a Unidyne III 545 (no switch) a try and compare it to my SM57.

The mic has a 4 pin connector (which I've since learned is an Amphenol MC4F). However, the mic came with a cable that has a matching 4 pin connector on one end and what appears to be a 1/4" TRS on the other end and says "Switchcraft."

I tried plugging in the 1/4" to a preamp, and I don't hear anything on when the preamp input setting is 'low-impedence/mic'. When preamp input is instead 'high-impedence/inst' setting, I can hear sound when I tap the side of the mic, but no sound when I speak into it.

So here's my questions:
1) Does it seem like I bought a broken mic, or is it that I don't have the right cable/connector?

2) If it's a cable issue, how do I go about getting the right connectors? I've seen some posts about soldering the necessary 4 pin-XLR cable, but I'm not sure exactly what I need. I would like to use this as a lo-Z mic ultimately.

Thanks for your help...I don't mind building/making a cable, but I definitely don't want a broken mic.

[mbrebes]

Here's a link for the pdf file for that microphone. The mic is wired for high impedance at the moment. There should be three wires and a ground in the cable, if you open the 1/4" plug. You will need to use the two unused wires and the ground, and attach them to an XLR connector. Page 2 of the pdf shows you which connections for low impedance.
******//www.shure.com/ProAudio/Downlo...nt5_NextRow=76

[milet22]

Thanks for posting that data sheet.

Having never wired a cable before, I'm a bit confused.

The data sheet says for balanced, low impedance use, BLACK (pin 3) and WHITE (pin 4) are hot and SHIELD (pin 1) is ground.

On an XLR, pin 1 is shield, pin 2 is hot, and pin 3 is cold.

How do I connect the 3 pins on the mic (amphenol) to the 3 pins on the XLR? I'm guessing ground to ground, but how do the two hot leads on the mic connect to the hot and cold of XLR?

Thanks

[mbrebes]

According to the data sheet, pin 4(white) would be Hot or +, and pin 3(black) would be Cold or -. Pin 1(ground) is ground. So it would be the following:
Amph--------------XLR
4--------------------2
3--------------------3
1--------------------1

Hope that answers your question.

[milet22]

Thanks for the pin info.

I found a cable that works (amphenol to 1/4" TRS) and it's configured for low impedance. However, same problems with the signal level.

I was told that the mic was working before I bought it, and assuming that to be true, any other thoughts?


Thanks...

[mbrebes]

The mic is working. You proved that by getting signal when set for instrument/high impedance input. You just need to understand your interface, which I have no experience with. It sounds like "low impedance mic" looks at the XLR and the other selection looks at the 1/4" plug. If you want it to work as a low impedance mic, you will have to put a XLR connector on the cable and plug it in that connection. If it is a combo connector(XLR & 1/4"), you need to understand that it is still wired as two different connectors. They don't go to the same place in the circuitry.

[milet22]

I understand your point about the low and high impedence selection affecting the XLR and 1/4" combo plug.

However, when I connect the mic with an TRS-XLR adapter, I have the same problem...I can hear "thumps" when I tap the side of the mic, but nothing when I speak into it. Again, this is using the XLR.

Thanks...

[mbrebes]

I would not recommend that you use an adapter. Can you verify with a meter that it is wired as I wrote in my previous reply?

Open the amphenol connector. Are there wires going to all four pins? If yes, then you have all those wires available at the other end of the cable. Remove the 1/4" TRS and install an XLR. If not, then you will need to make a new cable using the existing amphenol connector, with it wired as in my previous reply.

If you choose not to wire as has been recommended, then please don't ask for more help.

[milet22]

I don't have a meter at my house so I can't verify the pin outs right now. However, I opened the cable and I do have all the pins available. After the holiday, I'll be able to wire the XLR straight to the amphenol as you described, and I'll post the results.

I appreciate all your help...

[milet22]

The wiring you suggested still didn't solve the problem.

Shure customer support said it was either a broken capsule or possibly a broken transformer. For a $55 replacement fee, they'll replace it with an SM57.

Thanks for your help.

Anyone want an amphenol cable?

[Steamy Williams]

Originally Posted by milet22

Anyone want an amphenol cable?

PM'ed you.