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DIY Amphenol Mic to Phone Cable

If you have an old lap steel, PA amp, or amateur radio transmitter, you might be familiar with the screw-on Amphenol microphone connectors - the ones with one connector in the center.

The Amphenol series for these are 75-MC (with an M or F suffix for male or female), also numbered 8075-MC.  Switchcraft made them too - they'd be a 2501F or 2501M.

 At any rate, millions of these things were made and are still in circulation.  I have a handful which I use to make up cables with the Amphenol plug on one end and a 1/4 phone jack on the other. Some folks will convert their instrument or gear to a 'modern' jack, but there are enough of these connectors still around that we can make up a proper cable instead.

Here's how we make one up.  I like working with these connectors - they're easy to assemble and they're super reliable.

I try to buy these up when I can so that I have a few on hand. Usually they've been used and frequently have a hunk of old cable attached.

Easy to take apart. Step one is to remove the screw on the shell.

Unsolder the center (hot) connection from the button in the center of the connector.

Nice and clean now.

The spring and cable will now slide out.

Note how the shield on the cable was soldered to the spring.

Unsolder the shield from the spring and you'll have a disassembled Amphenol connector.

I used desoldering braid to get all the old solder off the spring. Then I cleaned it up with an abrasive soldering tip block.

We're going to solder our new coax shield to the spring, so cleaning it up will made soldering easier.

Line up our new cable alongside the connector and mark the cable where we'll strip the jacket off.

Here's the stripped cable read to be prepared to go into the connector.

That piece of cable jacket looks like some kind of pasta shape - maybe it's Cavolini No. 2 or something. (Cavo = cable in Italian).

This is Canare GS-6 cable, by the way. Great stuff.

Slide the cable into the spring and pull the shield back over the smaller end of the spring.

The shield will have to be trimmed back - this is a bit long.

Solder the shield to the spring.

Don't use a lot of solder - if it's too thick it will be hard or impossible to fit into the body of the connector.

Then trim the center insulation to expose the center lead.  Sorry, I didn't get a picture of that. Easy to figure that out.

Slide the body down over the cable.  You can leave enough of the center lead so it protrudes from the middle of the connector.

Then solder it in place.

How easy is this?

Trim the center lead and there you have it - a little button which will connect the mating surface on the jack.

Don't forget to put the screw back on.

The whole thing is quite rugged and will resist having the cable pull out of the connector.

The built-in spring strain relief is a great touch.

Really a clever design, don't you think?

Solder your connector of choice on the other end of the cable. I put a Neutrik phone plug on this one - it's going to be used with an old Supro lap steel.

Phone plug ready to go.

The whole cable is about 10 feet in length.

I forgot to get a shot of the whole thing - it took like 10 minutes to do this so I was just working away and forgetting to take pictures of everything.

You can probably visualize a red 10 foot long cable with an Amphenol connector on one end an a phone plug on the other! :-)

I test the cable for continuity with a DMM, then the 'reality' test is with my old Supro lap steel.

Works perfectly. This one is going off to a lap steel player in Florida. Another vintage lap steel back in service with the proper connector.


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