Four-quadrant mult

Freq Band · Joined: Sep 05, 2006 Posts: 57 Location: Los Angeles

By "deep" I mean, it seems to wear many hats. The web reveals it could be a VCA, RingMod, oscillator, and help prove various chaos theories.....
http://www.urel.feec.vutbr.cz/ra2007/archive/ra2006/abstracts/005.pdf
Razz

I'm attempting this one:
"4ch Four -Quadrant Multiplier" by Jonatan Liljedahl
http://www.synthdiy.com/files/2005/kyma_multiplier.pdf

First off, might there be a reason he uses 2 tl072's ?
I'm going to try it with a quad opamp.
What do 'ya think the pots' values might be ?
Do you have any good ideas on what I could do with the other unused half of the MLT04 ? (I might put a duplicate circuit on the other half of the board.)
I happed to find 4 of these MLT04's (pulls).

mosc · Posted: Sat Sep 16, 2006 2:07 pm Post subject:

I think one quad op amp would work, that the pot might be 100K.

Check out http://www.musicfromouterspace.com/analogsynth/RingModulator/RingModulator.html

State Machine · Posted: Sat Sep 16, 2006 6:49 pm Post subject:

The LM1496 is a neat chip to play with also. It can also be used to produce product terms. For example, inputting the same signal on both carrier and modulation will product a squaring circuit that produces double the frequency when using bipolar signals. The PAIA 9710 VCA/Mixer uses this IC. I have a few extras in my parts bin also.

http://web.mit.edu/6.301/www/LM1496.pdf#search=%22LM1496%22

Mosc, I like that AD633 chip also !! The Blacet "Klanc Werk" module uses this IC and I can get some CRAZY shit out of this thing when modulatiing from complex waveform sources! Very Happy

http://blacet.com/KW.html

Bill

mosc · Posted: Sat Sep 16, 2006 7:26 pm Post subject:

The 1496 is fine, but it needs trimpots. The AD633 is laser trimmed. For so little money, you might as well go hi-tech...

State Machine · Posted: Sun Sep 17, 2006 7:45 am Post subject:

bugbrand · Posted: Sun Sep 17, 2006 9:46 am Post subject:

...&, as ever, AD633 is available as a free sample from www.analog.com - I've had plenty of them over the last 6 months and they're great for really simple but powerful ringmods yes yes yes!

mosc · Posted: Sun Sep 17, 2006 12:33 pm Post subject:

Back to the topic.

The AD633 has some great freaturs other than laser trim. It has builtin op amps on the two inputs, and one on the output.

Why not use these anytime you need a mixer? It's just as easy to use as an op amp, but it makes the mixer stage voltage controlled.

These multiplier ICs can be used as single chip VCAs and the can be used like a voltage controlled resistor in many applications.

Why not use them on any input? and for that matter, on every output? Then you have the potential to add voltage control to just about every point in the circuit. You can choose not to use that voltage control, but it's nice to have easy to wire it up.

It's a good building block to master - like the op amp.

Funky40 · Posted: Sun Sep 17, 2006 3:06 pm Post subject:

That is very very interesting what you are telling mosc.

Really as easy as with op amps ?

What you say is maybe the solution for many things i was thinking about the last Days.
But i just learned to build a mixer on Breadboard this Days.

Dou you know (simple? )schematics where this things are done allready ?

edit: do i understand right: you suggest to use the AD633 instead of normal OP amps ?

Scott Stites · Posted: Sun Sep 17, 2006 4:07 pm Post subject:

Yes - Mosc sprecht the truth I use mine as a voltage controlled attenuverter quite often, for example.

Cheerio,
Scott

Freq Band · Joined: Sep 05, 2006 Posts: 57 Location: Los Angeles

Can these chips be used as oscillators?

I've built the circuit, but have not yet powered it up. I need to build a +- 5v psu (for the MLT04......the AD633 is "up to" +- 15v I believe ??).

This may be off topic, but Mosc mentioned "...voltage controlled resistor..... ", and I remembered seeing datasheet apps using opamps configured as a FDNR (frequency dependant negative resistor). Is this of some use in a synth module ?

=FB=

mosc · Posted: Mon Sep 18, 2006 6:09 am Post subject:

I mentioned using the multiplier as a building block on inputs and outputs as food for thought. I don't do building myself anymore and I can't provide schematics. Maybe someone else can do that.

As for a voltage controlled resistor, the multipler itself won't do that too well I don't believe. A resistor has the E=IR response. So if you want to control a currant, then the OTA is a much better choice. What I was saying is that in many applications people use a Varactor as a sort of voltage controlled resistor to makie voltage controlled gain stages. While a little bit more expensive, the 633 would do that function, and much more accurately.

I'm sorry if my thinking out loud was confusing...

State Machine · Posted: Mon Sep 18, 2006 7:49 am Post subject:

mosc · Posted: Mon Sep 18, 2006 10:27 am Post subject:

Yes, the op amp is pretty easy to understand for non-engineers. I think something like the 633 is too. The OTA is more difficult. Much for DIY synth design involved glue - finding useful and creative ways to hook up modules. OTAs are almost invaluable for building filters and oscillators, but the 633 could make designing glue a lot easier.

As DrJustice says, and now back to our regularly scheduled program... Very Happy

bugbrand · Posted: Mon Sep 18, 2006 1:23 pm Post subject:

...most interesting...

I wish I was more understanding with the engineering / electronics.

And, yes Freq Band, the AD633 datasheet does give an example of VC quadrature osc (along with some other things such as squaring and division that I really oughta try out on the g2)

State Machine · Posted: Tue Sep 19, 2006 6:53 am Post subject:

bugbrand · Posted: Tue Sep 19, 2006 9:42 am Post subject:

Hehe -- I've done a plenty of maths over the years up to degree stuff (yup, engineering based) - but, you know, it was never particularly tied in to anything really practical - always seemed abstract and kind of kills the creative buzzes. Maybe it was the way it was taught - I love the crossing of science and art but there wasn't much of that in the department (Son, you need to get yourself a proper job!) Never had more than a fraction of actual electronics taught to me - all been picked up by all the wonders of info about on the net and a few books..

State Machine · Posted: Tue Sep 19, 2006 10:10 am Post subject:

mosc · Posted: Tue Sep 19, 2006 1:32 pm Post subject:

Well, I have a masters degree in electrical engineering and specialized in IC design. My advice is don't worry one bit about what goes on inside an IC, its very complicated and everything changes over time as the technology evolves anyway.

Just learn the simplified model for an ideal op amp (infinite input impedance, infinite gain, zero output impedence, zero input offset voltage) and use the multiplier and other chips as ideal black boxes.