[sdiy] MC1495 multiplier chip discontinued completely

[Scott Gravenhorst]

And I *still* have not built an audio ring modulator.

I have a need for a very basic ring modulator, I have as choices: 1496
and AD633.  I also have LM13600 and LM13700.  Of these, what is the
best choice for this?  I don't plan to use it in a pitch shifter, just
for timbre modification to get metallic sounds.  Will one of these
work well enough for this purpose?

Also, on the other end of the scale are really poor multipliers, like
using a single FET which I guess is a one quadrant "multiplier".  Very
nonlinear, but does this have viable uses?  After all, if one can do
it to square waves with an XOR gate, an FET should be useful for
*something*.  

Watching this decay into "unobtainium" is depressing...

>From: "Czech Martin" <Martin.Czech at Micronas.com>
>> I just learned from Arrow/Spoerle that the MC1495 multiplier chip
>> is discontinued and they can not ship any more.
>> On Semiconductor has accordingly made an update to their
>> web site. 
>> 
>> So I guess the 1495 is *really* gone.
>> 
>> The good thing about this chip was that it contained more
>> or less matched transistors for the gain cell, so offset and offset
>> drift was under control. I.e. carrier suppression was good.
>> Compander circuits will not make a good job for this carrier
>> suppression, because it is not a wide band noise problem,
>> but very narrow, so masking is poor.
>> 
>> And it had an input linearisation circuitry for the 
>> carrier input, in order to have quite linear behaviour.
>> The (still available) 1496 is designed for square wave
>> carrier and has of course no input linearisation.
>> So you have to use low carrier amplitude (noise)
>> or accept excessive sidebands (distortion, intermodluation).
>> Also the 1495 allowed to taylor the gain cell bias current.
>> For good S/N you need a lot of current.
>> Most other integrated multipliers do not allow for bias
>> current change and are designed for low power consumption,
>> so S/N of 80 dB will be the upper limit, and most devices
>> will not even give that (AD633 for example).
>> For some applications this is still too much noise.
>> 
>> I want low noise and linear behaviour (smooth sound).
>> So next I try the RC4200 (?) and the 1496 with external DIY
>> linearisation stage. If this doesn't work I'll go back to
>> a complete discrete design, perhaps using a couple of
>> japanese dual NPN, glue, expoxyd ... whatever it takes
>> to cope with the offset problems...
>> 
>> 
>> m.c.
>> 
>> 
>> 
>

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