LZX Cadet X - DIY Video synthesizer - Multiplier

There is a old saying in the audio world: "You can never have enough VCAs"
Maybe this is a bit simplistic, but I'm seeing the Multiplier as a VCA for video.
(its much more than this too).

These are some pics of the Cadet DIY modular video synth build.
I am an independent builder and have nothing to do with LZX industries.
These aren't official build notes, just my records to help me trouble shoot.
It's a work in progress.
Do let me know if you spot any errors or omissions.
This is module no.10 (Multiplier X).
It doesn't require the 14 pin sync cable.

It's described as "Cadet X Multiplier is a variation on the Cadet VI Fader circuit,
 configured as a switchable 2-quadrant or 4-quadrant multiplier".
So if I understand this correctly, in 2-quadrant mode it it acts like a VCA and in 4-quad mode it behaves like a ring-modulator..... "it crossfades between an inverted version of the input signal
and a positive version of an input signal"

2-quadrant mode = VCA.
You can control the amplitude with a control voltage (0 = no signal & 1V = max signal)

4-quad mode = Ring Modulator
The amplitude of the output is again controlled by CV.
When CV is negative ( -1V for LZX = max inversion) signal gets inverted.
When CV is positive  ( +1v on LZX = max amplification) signal is non-inverted.

..

This video amp ic is out of stock at mouser. (marked U2 on the PCB)

Mouser No:

584-LT1251CN#PBF

Mfr. No: LT1251CN#PBF 

I'm using this instead:

Mouser No: 584-LT1256CN#PBF

Mfr. No: LT1256CN#PBF

LT1251CN#PBF - iTS a 40MHz Video Fader and DC Gain Controlled Amplifier
It's probably the core component of this module. Looks very useful if you are designing your own circuits like the fader and amp below. But its not cheap. Mouser sell them for $16 AUD each.

And yes, this same chip is used in the Cadet VI Fader module.

ICs and special parts:
TL072IP
LT1251CN#PBF  ---- 40MHz Video Fader and DC Gain Controlled Amplifier
LM6172IN/NOPB
TL431BQLPR

to be continued ... waiting on some parts

Links:
LZX official
Muffs - Cadet series DIY/assembled

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