Replace 566?

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man0111
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Replace 566?

Post by man0111 » Tue Feb 11, 2020 6:19 pm

There are a couple Thomas Henry circuits that I'd like to build which call for 566s. 20$ for a (maybe) original is out of my limited budget, and playing the Chinese lottery for 5$ each doesn't sound much better.

How realistic would it be to just replace with a simple op-amp oscillator, for example?
The datasheet mentions that the 566 is very temperature stable, is it somehow compensated internally beyond what I'd achieve with the matched transistors/tempco method?
The first thing I was thinking of building was his "tunable noise" circuit which is quite simple. I thought maybe I could get away with kludging in a simple vco, since the circuitry for 1v/oct doesn't seem that in-depth, (no tempco or trimmers, although that comes back to my first question), and I'm assuming it isn't really meant for precision playing.
A thread on electro-music mentioned replacing with xr2206, which is 10$.. and I found a few other oscillator packages.

I guess the point is that I don't really know what I'm trying to replace other than a simple vco.
Any help? :help:

Edit: forgot to drop in the circuit in question
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I gotta take a minute here to say thanks to everyone out here since it's my first few posts. I've been lurking around here and electro-music for a long time and the knowledge sharing is immense, something that's occasionally awe- inspiring in the world we live in.

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Re: Replace 566?

Post by guest » Tue Feb 11, 2020 6:39 pm

the 566 isnt a great VCO, so it should be easy to replicate (its not exponential). for a triangle wave, a standard opamp VCO might be the easiest, but LM13700 and 4046 VCOs would work as well. for a sawtooth wave, a 555 based VCO would be easy.

[EDIT] looking at the rest of the circuitry, id reccomend a 13700 based VCO to match what is already there.
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man0111
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Re: Replace 566?

Post by man0111 » Tue Feb 11, 2020 6:43 pm

Cool, so I'm not missing any magic, then. Thanks!
I gotta take a minute here to say thanks to everyone out here since it's my first few posts. I've been lurking around here and electro-music for a long time and the knowledge sharing is immense, something that's occasionally awe- inspiring in the world we live in.

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Re: Replace 566?

Post by guest » Tue Feb 11, 2020 6:58 pm

yeah, just build Figure 33 from the LM13700 datasheet.
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The Peasant
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Re: Replace 566?

Post by The Peasant » Wed Feb 12, 2020 1:46 pm

Mr. Henry himself used that LM13700 datasheet circuit for a LM566 replacement in his Bass++ project:

http://www.birthofasynth.com/Thomas_Hen ... _Plus.html

I made a few modifications to the circuit to better suit my needs:

http://www.electronicpeasant.com/projec ... ssbox.html

Take care,
Doug
The Electronic Peasant

www.electronicpeasant.com

Studioalethea
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Re: Replace 566?

Post by Studioalethea » Sun Feb 16, 2020 3:14 pm

I just made a simple 566 VCO based on the data sheet and the information in Elliott Sound Projects (#162). It seems like its main benefit was just how easily you could get a waveform out of it. I just happened to salvage a chip in some gear we were throwing out at work. Some older wireless microphone systems used them.

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