[sdiy] MC1495 multiplier chip discontinued completely

[Czech Martin]

>http://www.oldcrows.net/~jhaible/tonline_stuff/jh1_ring.gif

I saw a similar one OTA circuit in EN, also temperature
offset problems.


>The most funny thing in terms of RM design is that there is a circuit
>which deliberately uses class B (a real gap, though ever so tiny) instead
>of class AB or whatever. That's from ARP (as used in the 2500
>or 2600, maybe in both, I don't remember), and it has a reputation
>of being especially *clean* !!
>
>Why? Because clean can mean two different things: No higher sidebands
>from nonlinearity and/or no carrier bleedthru when you stop playing.
>Obviously the latter can be achieved even without perfect trimming
>if the *signal* (not the modulator) is fed into the input that suffers
>from the dead band.

!
True
I have the circuit somewhere...
!

The linearised 4 Q gain cell has a slightly similar behaviour.
The log input suffers from distortion, but at least my
discrete application shows some dead band. Maybe due to mismatch
and low base current behaviour (recombination will destroy
ideal expo behaviour for low currents), there is liess current then
predcited, similar to dead band somehow.

The other input is linear , and suffers more from offset problems.
Multiplication is commutative in theory, but both inputs
in this realisation are not equal by any means.
I think I liked audio-> log, carrier -> lin.

btw. it can be great fun to feed both inputs with the same signal.
One track of my CD #2 shows this: original on input a,
slighly delayed version on input b, so you get echo, octaving
and other strange stuff at the same time.
Still sounds musical to my ears.


m.c.