Hex VC mixer

[Magnus Danielson]

From: "Paul Maddox" <paul.maddox at ndirect.co.uk>
Subject: Hex VC mixer
Date: Mon, 10 Jul 2000 13:53:35 +0100

> Dear all,

Dear all,

I am just back from 2 weeks of holiday without an Internet connection, so I
have a huge backlogg... so I will not even consider checking for a proper
reply to this email...

>   I remember a while back a schematic for a 4049 based (I think) voltage
> controlled
> 6 channel mixer..
> 
>   anyone have a link/schematic?

No, but I recall the trick.

The 4049UB is an hex inverter consisting a N-channel and a P-channel MOSFET
transistor. The trick here is to use one of these transistors as an ordinary
FET variable resistor (using two resistors), use the common wiring of these
interters, namely the powerline as the summation point of the six channels.

So, for each channel you feed the CV into the input through an 1 Meg resistor,
you hook another 1 Meg resistor from the inverter output to the inverter
input. Now, feed your signal into the inverter output (yeah, you heard me!)
and use the 4069UB ground as an virtual ground summation point. Wire the
Vcc to ground to disable the upper half of the inverter.

Its pretty wierd and el-cheapo, but hey! It works! ;)

If I recall it correctly this thing was used by no other than Paia ;)

Cheers,
Magnus