[sdiy] returning to the chronic disappointment of the 1496...

[Tom Farrand]

An AD633 is "prohibitively expensive" at $7?  No, a Z-80A I paid $200
for was "prohibitively expensive" when I was making < $8/hour!

Peace.
Tom Farrand


On Thu, Jan 14, 2010 at 12:36 PM, <alfred.pear at gmail.com> wrote:
>
> Alright, apparently I was premature in denying the existence of AD633
> in an otherwise chaotic and indifferent universe.
>
> However, the $7 IC is prohibitively expensive when compared to the
> lure of a 50 cent LM1496.
>
> Jurgen, the doubled carrier frequency is the exact problem. I will
> take a much closer look at the modulation stage in your Frequency
> Shifter.
>
> I'm also very interested in your solution, David.. I'll commence
> pestering shortly.
>
> Thanks SDIY!
>
> -AP
>
>
> On Thu, Jan 14, 2010 at 1:31 PM, David G. Dixon
> <dixon at interchange.ubc.ca> wrote:
> >> Has anyone found any workarounds for the signal bleed-through problems
> >> with 1496s used as 4Q-Multipliers?
> >> I've read and re-read mailing list archives, message boards, and tried
> >> almost all the schematics I could find...I cannot seem to get the two
> >> signals to actually *balance* with real precision.
> >>
> >> With the 633s and 1495s off the market, there has to be a cheap,
> >> effective solution to ring modulation, right? Have OTA approaches
> >> yielded worthwhile results?
> >
> > Alfred, I have developed, built and tested a 4Q multiplier based on the
> > linearized SSM2164 (actually I use the Coolaudio V2164 -- $3.50 each at
> > Small Bear, or $3.00 for 10 or more).  It works very well.  I originally
> > developed the circuit based on the LM13700, and this also works very well,
> > but is a little bit trickier to set up.  In either case, I arranged the VCAs
> > in a "push-pull" arrangement.  One processes the carrier signal as is, and
> > the other processes the inverted signal.  Also, one is controlled by the
> > modulating signal as is, and the other is controlled by the inverse of the
> > modulating signal.  In the case of 13700, the carrier signal must be
> > dramatically reduced to avoid distortion, and the modulating signal must be
> > shifted carefully, but things are much more straightforward with the
> > linearized 2164.  I also have a pot which pans between the two carrier
> > signals such that at either extreme one obtains 2Q multiplication, in the
> > middle one obtains very well balanced, symmetrical 4Q multiplication, and in
> > between one obtains various degrees of unbalanced, asymmetrical 4Q
> > multiplication.  Finally, I've also brought both signals in through
> > variable-gain ideal rectifiers fitted with 3-way switches which allow either
> > +, +/-, or - polarity.  This adds a lot of unique functionality in CV
> > modulation, and creates some very subtle and interesting effects in audio
> > modulation.
> >
> > This circuit grew out of the desire to avoid spending beaucoup bucks on
> > "proper" multiplier chips like the 633, and also from the painful
> > realization that the (very simple) ring-mod circuit in the LM13700 datasheet
> > sucks really hard!
> >
> > Please email me if you are interested, and I can send you my design files.
> >
> >
>
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