[sdiy] Cool 'ring modulator' schematic

[David Brown]

I built this as well.  It is interesting.  No LO input bleeds through 
to the output. I tried a variety of waveforms on both inputs. You get 
all sorts of interesting artifacts out. I did try a comparator on the 
input to the LO.  That makes it interesting as it limits the effect 
ot just flipping polarity (e.g. it eliminates the other artifact)s. 
Then, you can play with the comparator level to generate a very 
narrow pulse for the LO input.  I put a quick scope image at
http://modularsynthesis.com/images/EN-mixer.jpg

I think I might build this with input buffers, an RF attenuator, and 
a LO input that is selectable through a comparator with a variable 
reference level.

Dave


At 09:01 PM 2/11/2006, harrybissell wrote:
>Hi Tim...
>
>ok you asked for it.
>
>Its VERY COOL. A must-have imho.
>
>It works well throughout the audio range. And don't believe the
>BS about the square wave. Use any waves you like.
>
>The article warns of 'distortion' but you will LOVE the distortion.
>I didn't find a setting I did not like ...
>
>I'd set it up with VCAs on the inputs.  Overall sound is dead
>quiet.  I used TL072s and 1% resistors.
>
>You can add a cap across the feedback resistor in the output
>summer... for HF rolloff. Might be neat to make that switch
>selectable.
>
>10K inputs are kind of low, a couple of buffer amps are a nice
>add.  Don't forget to put some series resistor in the output or
>the TL072 will go nuts !!
>
>BTW... check the schematic carefully. R11 and R4 are in parallel,
>so replace them withone 10K instead of two 20Ks
>
>H^) harry
>
>Tim Parkhurst wrote:
> >
> > On 2/8/06, harrybissell <harrybissell at prodigy.net> wrote:
> > > in the latest issue of Electronic Design (under Design Briefs)
> > >
> > > This is an opamp based design... it would be above the ARP
> > > 'exclusive or' design but below most true four quadrant
> > > designs in terms of functionality.
> > >
> > > READ the last paragraph... note the schematic says "rf"
> > > but in reality... 'radio frequency' in this design
> > > is probably not more than 10KHz   :^P
> > >
> > > Still, some may want to play. I might whip one together...
> > >
> > > H^) harry
> > >
> > ************************
> > Hey Harry,
> >
> > Could be interesting. Here's a link
> > http://www.elecdesign.com/Articles/ArticleID/11935/11935.html
> >
> > The writeup states that the design is 'limited to lower frequencies'
> > which sounds like it would work for audio just fine. Also looks like
> > it works with a variety of waveforms (unlike the square-only ARP XOR
> > design).
> >
> > Let us know how it works if you knock one out.
> >
> > Pretty please? ;)
> >
> > Tim (could be interesting) Servo
> > --
> > "Imagination is more important than knowledge." - Albert Einstein