General tech questions



I am (no kidding) posting for a friend — a tech question concerning his 1940s National lap steel he's in the process of selling. So, not a sale posting, a tech question.

I figure if someone knows, it would be here. My pal John wrote:


I have a late-40s National lap steel that I never play. So I'm going to sell it. But it's got a totally whacked plug. I stumbled across this photo on Reverb, as I was pricing, and I've added BIG yellow arrows (I hope they're visible). Does anyone know what kind of jack this is called? I 'think' I have a working cable for the guitar (stashed somewhere), but I'm curious what this plug is called for the listing I'll create, when I post it for sale. The 'jack' next to the bottom arrow, apparently allows for a ¼" guitar jack to be used. Anyone know where I can find a jack like that? But first, the name for this particular plug. Anyone?


AKA an Amphenol plug / Amphenol jack.

Used mainly on old crystal mics, but also found on other vintage gear from time to time. It's usually a high-impedance 2- conductor connector, impedance is often around the same as modern 1/4" inputs, but sometimes (in the case of certain microphones, like old ribbon transducers) it can be lower than standard "high impedance", which can result in an impedance mismatch. However, I would suspect that for a lap steel, you'll be OK on the impedance matching.

And yes, you can still get parts-- these connectors are still used very frequently by harmonica players using vintage microphones.


Amphenol connector is correct. '40s-'50s tech. Used before Cannon plugs, then XLR. Same 5/8"-28 threads as a mike stand. Glad to see they can still be acquired.


Youse guys rock. I think I can speak for my friend John, "thank you kindly" ...


I have one of those jacks on my 50’s Supro lapsteep.


Amphenol connector. You can get them at any real electronics place.

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