What to do with obsolete microphone inputs?

[Rhodesplyr]

When restoring an older guitar amp that has obsolete screw-mount microphone inputs in addition to 1/4" inputs, what do you usually do with these? Remove them? Disconnect them? Leave them alone?

Does anyone ever make screw-on shields for these?

[g1]

Depends what you mean by "restoring" I guess. To stay true to the original, they should be left in circuit. There are probably still adapters available to plug high impedance mics into these kinds of connectors. Or even old mics that use them. Otherwise, replacing with 1/4" jacks would probably be the way to go.

[Enzo]

There are screw on adaptors, but then you have them sticking out.

If the mic thing is wired parallel to the 1/4", first is it causing noise or not? If not, ignore it. If so, then drop the wire off it and leave it there for appearance. Or do what g said and install another 1/4 jack.

And they used to make the things with grounding contacts even. A metal washer in there shorted across it, then screwing the connector onto it pushed the center down and un-shorted things.


Or tell the customer they will have to get special guitar cords with the screw on ends.

Try to keep a straight face.



Switchcraft call those the 2501. They came in male and femals, the only difference being the thread ring screwed on. I don;t know of commercial caps, but one could take the ring and insert a metal disc and have a screw on shield, maybe a penny or a nickel.

The thread on it is 5/8-27, so you could be creative.

Switchcraft 332A was the adaptor, screw on to 1/4 female.
http://www.switchcraft.com/Drawings/332ax_cd.pdf

They also made the 5501 series which are the same thing but only half the size. I have a bunch of those, I doubt I will ever use.

[Rhodesplyr]

The ones I'm dealing with are parallel with the guitar inputs, so, if they were shorted, the 1/4" inputs would be as well. It is possible to touch them accidentally on the control panel and cause momentary noise. In this case, perhaps it would be best to disconnect them and leave them for appearance--though their aesthetic value would be at least a matter of debate.

[Gtr_tech]

When you pull those old style hi-z mic connectors out, the panel hole should be the same size as the cutout for a 1/4" jack. Replace with those in a non sorting variety.

[Enzo]

Yep, should be 3/8" bushing.

[Rob55]

So I am a completely ignorant novice. I bought a "1920" Coronette tube amp off ebay for $15. It has a small speaker two knobs and one threaded input. This is from pictures. It's not here yet. Sounds like I can perhaps recap it, put a threaded connector on one end of a guitar cable, note my straight face, and play. That's if the transformers work. I only need a 1/4 plug on one end for it to work right. I will send pictures. From my checking out the sight I know you will want me to draw or scan a copy of the schematic. Anyway I'll be looking for help. I hope to have at least the transformers, cabinet and chassis to work up a low power living room amp. Thanks Rob

[Enzo]

Hi, welcome to the forum.



Yep, make up a special cord. Or swap the screw-on for a regular 1/4" jack. Should fit the same hole.


In a beat up ollllldddd amp, the transformers are the part I'd have the least concern over. Caps will be the main issue, age-wise.

We like a schematic when we help troubleshoot. But really, if you recap it and it works, then there you are, no drawing required.