09-12-2016, 05:41 PM
A HANDY HEADPHONE MATCHING UNIT
This headphone matching unit was devised and built today. It is for matching normal low-impedance headphones with a stereo jack plug to, small valve receivers, in order to remove the need for a matching transformer in each project.
Basically, it is an LT44 audio transformer with the high impedance leads going to a mono 3.5mm jack plug. The low impedance leads (one half of the centre-tapped section) goes to a 3.5mm stereo jack socket wired for mono.
I had to rack my brains for a suitable container, but when my glue stick dried up, it occurred to me that it was perfect for the job. I sawed off the end, and pulled the insides out, and washed it thoroughly. I fitted a wooden plug in the open bottom end, and filled in the gaps with P38 car paste. The whole thing was then rubbed down with wet & dry paper to obtain a suitable surface for painting. I drilled a hole in each end, one for the input lead, and the other for the output jack socket. I sprayed it with aerosol grey matt primer car spray from Halford's. After wiring it up, I packed each end with a bit of bubble wrap for insulation, and snapped the top (containing the 3.5mm output socket), back on.
In the image, it appears to have a pinkish colour, but that is because I photographed it in artificial light. It is a light, matt grey in the light of day. It has quite a professional look to it, is light and handy. No-one would imagine it was a glue stick. Works a treat.
Bob
This headphone matching unit was devised and built today. It is for matching normal low-impedance headphones with a stereo jack plug to, small valve receivers, in order to remove the need for a matching transformer in each project.
Basically, it is an LT44 audio transformer with the high impedance leads going to a mono 3.5mm jack plug. The low impedance leads (one half of the centre-tapped section) goes to a 3.5mm stereo jack socket wired for mono.
I had to rack my brains for a suitable container, but when my glue stick dried up, it occurred to me that it was perfect for the job. I sawed off the end, and pulled the insides out, and washed it thoroughly. I fitted a wooden plug in the open bottom end, and filled in the gaps with P38 car paste. The whole thing was then rubbed down with wet & dry paper to obtain a suitable surface for painting. I drilled a hole in each end, one for the input lead, and the other for the output jack socket. I sprayed it with aerosol grey matt primer car spray from Halford's. After wiring it up, I packed each end with a bit of bubble wrap for insulation, and snapped the top (containing the 3.5mm output socket), back on.
In the image, it appears to have a pinkish colour, but that is because I photographed it in artificial light. It is a light, matt grey in the light of day. It has quite a professional look to it, is light and handy. No-one would imagine it was a glue stick. Works a treat.
Bob
