Vintage push button mic Identification help needed please?

[SoundChap]

Hi,
I'm new to this forum and this is my first post so please be gentle with me. I recently purchased a microphone from an electronics shop in Lincoln hoping to convert it to XLR to plug into an audio interface to give an authentic 1930's sound (hopefully) I've scoured the interwebs looking for anything similiar and also to find whether the plug/cable is an early 5 pin xlr or otherwise and also to see if I can source a pin-out to convert from 5 to 3 pin but unfortunately I can't find any information that may be relevant apart from it seems that the plug may be to connect to either a public announcement system or an old ham/cb radio setup. I've attached pictures and it appears to be made from bakelite but I'm unsure but it does have 'Marconi Mobile' written on the base which obviously I've checked but it seems to throw no clues as to its origins. I wonder if anyone could please shed some light on this? I don't want to just cut the plug off and try wiring an xlr without checking first that it might have some history that would push me to keeping it in its current form but I did buy with the intention of using it. Thank you in advance for any information you might have wether large or small.

[Graham G3ZVT]

More 1980s than 1930s I'm afraid!
Your microphone can be seen on pg 4 & 5 of this brochure (Pg 8&9 of the PDF)

https://themarconifamily.pbworks.com/w/file/fetch/132968058/Marconi%20Mobile%20Radio%20.pdf

[SoundChap]

Thanks Graham, I would never have found this and yup that's the one! I guess I don't have to worry about it being vintage or valuable then!I don't suppose you could tell me if it would be possible to re-purpose itto plug into my audio interface/Mixer via 3 pin XLR? I just thought I might as well give it a go now and see what it sounds like! Thanks again, Mark.

[Graham G3ZVT]

Can you open it easily?
The first thing you need to determine is what kind of microphone it is, moving-coil, condenser, or given its use involving a telephone line, it might just be a carbon mic.

A picture of the mic insert would give us a clue and some probing with a multimeter would confirm.

[CambridgeWorks]

Its a two way radio base station microphone. The types made by GEC. Has their classic type of plug. Not sure if some were marketed as Marconi?
It will be a moving coil, impedance probably 2k or so.
I have one somewhere. Their radios were mostly fm, in fact not sure if am were made, certainly not in the 70s/80s which this dates from.
Rob

[SoundChap]

Thanks for the further replies! In response to being able to open it there's a small set screw at the back which I've undone and tried to prise the top off with no joy, the bottom has a very well stuck down felt pad which i probably could 'dig' into but I'm thinking it would make a mess and I do like the look of this mic if i was able to re-wire it for purpose and so feel it's best not to. Graham pinpointed it with the brochure he linked to and it is some type of base station mic. I have various microphones for music making/voiceovers but I'm no expert, would this require phantom power when using with an audio interface if (and only if!) I figured out how to re-wire for XLR and do you think it would be possible to rewire due to the fact it has a (i would imagine) press to speak button? The 'plug' does unscrew and so reveals four wires (despite the 5 pins) which I'll send a picture of shortly. It's a little confusing to me as it comes across as a type of DIN (MIDI) plug with the pin arrangement but also comparing it to a MIDI din plug male or female its much smaller.

[SoundChap]

Here's some pics, thanks again for your interest in this I do appreciate it.

[Chrispy57]

Hi - from the details in the linked brochure it's likely the 4 wires are 2 each for the microphone's audio output, and the push to talk switch. You can find which two are for the switch with a meter on the Ohms range, whilst pressing the switch the reading will go from open circuit to short circuit. The microphone's output level is 1mV and its impedance is quoted as 300 Ohms. No phantom power required since it is not an electret microphone.

Cheers
Chris

[SoundChap]

Thanks Chris I've got a multimeter so I will try that, I've never heard the term electret microphone before but obviously that shows my knowledge, I'll get a meter on it tomorrow when see what I can do thank you so much.

[CambridgeWorks]

Mine was last used around 15 years ago on my home made 1.8 -2Mhz solid state transmitter.
Occasionally gave some rf feedback howling, no doubt due to antenna being a couple of metres away.
Rob

[paulsherwin]

Originally Posted by SoundChap

Thanks Chris I've got a multimeter so I will try that, I've never heard the term electret microphone before but obviously that shows my knowledge, I'll get a meter on it tomorrow when see what I can do thank you so much.

https://en.wikipedia.org/wiki/Electret_microphone

[SoundChap]

Thank you! I wish I'd found this group earlier it seems there's a lot of people dedicated to the subject. I appreciate your help, I really do! ??

[SoundChap]

Originally Posted by SoundChap

Thank you! I wish I'd found this group earlier it seems there's a lot of people dedicated to the subject. I appreciate your help, I really do! ??

Sorry about the question marks I don't know how they got there!

[SoundChap]

Originally Posted by paulsherwin

https://en.wikipedia.org/wiki/Electret_microphone

Thanks for the info link