Homemade Microphones - UK Vintage Radio Repair and Restoration Discussion Forum

Goldieoldie · 28th Aug 2014, 10:09 pm

When I was a young lad (many moons ago ) I used to make carbon Mics by filling a miniature polish tin (Betterware ?) with filed down dust from a battery carbon centre electrode .
The top was covered with tin foil forming the mouth piece.A wire insulated from the tin was poked through a hole in the base of the tin into the carbon dust.It worked quite well wired with a 4.5 v light battery in series with a home made receiver which was made winding a coil around a magnet and a baked tin lid as the earpiece!

unitaudio · 30th Aug 2014, 12:21 am

This is a good illustration of just how basic you can make something and still have it work! How did you arrive at the idea?

Regards,
Paul

lesmw0sec · 30th Aug 2014, 9:19 am

I made a couple of condenser mics many years back, with an insulated back plate having a thin stainless steel membrane stretched over this with a small air gap. A built in pre-amp using an ECC81 in cascode gave a very good performance. The extreme HF response was a bit poor though, probably due to the thickness of the membrane.

Herald1360 · 30th Aug 2014, 6:03 pm

When I were a lad.....

My father made a microphone based on some pictures in a BOP annual from the 1890s in a series on how to make your own telephones (literally from the sort of materials that were available to an enthusiastic youngster then). Dad's version involved the carbon rod from a U2 and a couple of dynamo brushes (he was a mechanic). A hole was drilled in each brush and the ends of the rod turned down to be a loose fit between the two brushes- the shoulders on the rod stopped it from falling out. The brushes were fixed to a piece of wood by passing their tails through suitable holes and retaining them with choc block terminals. In series with a 3V battery and a headphone set it worked quite well!

Goldieoldie · 30th Aug 2014, 6:51 pm

Hi Paul,
It was so long ago I can't remember how I came up with the idea.Possibly at the age of 10 ish it was driven by lack of funds!
Cheers,Pete

jay_oldstuff · 31st Aug 2014, 10:52 am

I remember building a carbon granule MIC back when i was 9 years old and had seen it done on the TV show The secrete life of mashies. it used a plastic coffee jar lid with two pieces of silver foil stuck to the base. this was filled with carbon granules and a plastic disk put on top to act as the diaphragm. it worked quite well connected to a 6v lantern battery and an old HiFi speaker

Jay

jim_jobe · 1st Sep 2014, 5:30 pm

One that I made back in 1963 consisted of an inverted cigar box with two razor blades stuck in so that they were parallel to each other. A carbon rod, ex battery, was laid across the tops of the blades and wires and a series battery attached to them. It worked a treat.

28th Aug 2014, 10:09 pm	#1
Goldieoldie Octode Join Date: Jul 2014 Location: Petersfield, Hampshire, UK. Posts: 1,043	Homemade Microphones When I was a young lad (many moons ago ) I used to make carbon Mics by filling a miniature polish tin (Betterware ?) with filed down dust from a battery carbon centre electrode . The top was covered with tin foil forming the mouth piece.A wire insulated from the tin was poked through a hole in the base of the tin into the carbon dust.It worked quite well wired with a 4.5 v light battery in series with a home made receiver which was made winding a coil around a magnet and a baked tin lid as the earpiece! Last edited by AC/HL; 29th Aug 2014 at 2:57 am. Reason: Thread split

30th Aug 2014, 12:21 am	#2
unitaudio Heptode Join Date: Sep 2013 Location: Manchester, UK. Posts: 862	Re: Homemade Microphones This is a good illustration of just how basic you can make something and still have it work! How did you arrive at the idea? Regards, Paul __________________ ...No, it's not supposed to pick up the World Service, it's not a radio!

30th Aug 2014, 9:19 am	#3
lesmw0sec Octode Join Date: Jul 2009 Location: Carmel, Llannerchymedd, Anglesey, UK. Posts: 1,509	Re: Homemade Microphones I made a couple of condenser mics many years back, with an insulated back plate having a thin stainless steel membrane stretched over this with a small air gap. A built in pre-amp using an ECC81 in cascode gave a very good performance. The extreme HF response was a bit poor though, probably due to the thickness of the membrane.

30th Aug 2014, 6:03 pm	#4
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Homemade Microphones When I were a lad..... My father made a microphone based on some pictures in a BOP annual from the 1890s in a series on how to make your own telephones (literally from the sort of materials that were available to an enthusiastic youngster then). Dad's version involved the carbon rod from a U2 and a couple of dynamo brushes (he was a mechanic). A hole was drilled in each brush and the ends of the rod turned down to be a loose fit between the two brushes- the shoulders on the rod stopped it from falling out. The brushes were fixed to a piece of wood by passing their tails through suitable holes and retaining them with choc block terminals. In series with a 3V battery and a headphone set it worked quite well! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

30th Aug 2014, 6:51 pm	#5
Goldieoldie Octode Join Date: Jul 2014 Location: Petersfield, Hampshire, UK. Posts: 1,043	Re: Homemade Microphones Hi Paul, It was so long ago I can't remember how I came up with the idea.Possibly at the age of 10 ish it was driven by lack of funds! Cheers,Pete

31st Aug 2014, 10:52 am	#6
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Homemade Microphones I remember building a carbon granule MIC back when i was 9 years old and had seen it done on the TV show The secrete life of mashies. it used a plastic coffee jar lid with two pieces of silver foil stuck to the base. this was filled with carbon granules and a plastic disk put on top to act as the diaphragm. it worked quite well connected to a 6v lantern battery and an old HiFi speaker Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

1st Sep 2014, 5:30 pm	#7
jim_jobe Heptode Join Date: Nov 2004 Location: Ripon, N.Yorkshire, UK. Posts: 782	Re: Homemade Microphones One that I made back in 1963 consisted of an inverted cigar box with two razor blades stuck in so that they were parallel to each other. A carbon rod, ex battery, was laid across the tops of the blades and wires and a series battery attached to them. It worked a treat.