Old fashioned disco valve mixer.

[ckpr2]

Being an electronics design engineer I thought I would travel back in time to the 1960's and design myself a valve mixer for a disco.
It gives a clean sound.
It has 2 stereo channels a line input and a high gain microphone channel.
When people see it they have no idea what it is with two valves stuck out the top.
I just have to be careful when moving around that the glass valves don't get hit.
17147

[DJ Jules]

You've got to be using more than 2 valves for all of those channels? How does that work?

Julian

[dicky]

Probably he is using dual pentode or triode pentode valves and a Class A design which effectively give him four amplification stages with two valves - And modern solid state rectifiers etc for the power supply at a guess.

When I did my City & Guilds in TV Video & Electronic servicing back in the 80s we still had to learn valve circuit design and how to repair it - even though by then the technology (apart from the CRT) had been effectively obsolete for years.

I have a friend who is very much into valve tech and vintage/military amatuer radio - he doesn't call them valves though, he calls them 'bottles'

Rich

[ckpr2]

They are dual triodes.
One valve looks after the mic extra gain.
The other has one triode looking after line level gain.
The channels are mixed together before the gain stage.

[ckpr2]

Circuit diagram.
http://www.ckpr.talktalk.net/mixer2.jpg