[sdiy] 566 Functional Replacement

Oren Leavitt obl64 at ix.netcom.com
Mon Mar 19 19:49:26 CET 2018

How about a triangle (or saw) VCO core on a small SMD board piggybacked 
on an 8 pin DIP header?

On 3/19/18 11:26 AM, Tim Ressel wrote:
> When I sed 'VCO' I did not mean a full-featured volt per octave VCO. I 
> literally meant an oscillator that has voltage control. Cv in, 
> triangle and square out, thats it. thats what the 566 did. that is 
> what I want. 8 pins, 5 passives, and you're in business. thats what 
> the 566 brought to the party.
> -t-i-m-b-o-
> On 3/19/2018 9:21 AM, Mattias Rickardsson wrote:
>> Some thoughts about the dream VCO discussions here:
>> What would be the main reasons for wanting a tiny VCO IC?
>> I can find it hypothetically attractive, sure, but given that it will 
>> never have many features AND a small size at the same time, I'd 
>> almost always need to add stuff outside in the end since you rarely 
>> want just the basic functionality. If I'd use a dedicated VCO IC I'd 
>> rather have some features that are sometimes not in use than having 
>> to add near-basic functionality with external components. The only 
>> true reason for a small chip that I can come to think of is cost. I 
>> guess it somehow scales with size in IC fabrication?
>> Making wishlists with VCO features, ending up on the 3340 
>> specification from 38 years back... aren't we missing something? :-)=
>> Many modern analog oscillators (both in modulars and in hardwired 
>> synths) have other features than the ones we had in the '80s. This 
>> should be reflected a bit in the wishlists we make for VCOs today, 
>> even if most of these features could be added outside the main chip. 
>> Exponential and linear CV should be mandatory, 
>> triangle/sawtooth/square outputs as well - and I'm thinking that a 
>> triangle core would be the way to go, even if proper sync needs to be 
>> dealt with in a less obvious way. That said, we're still stuck in 
>> 1980. Sine shaper, thru-zero FM, what more is desired for the 
>> synthesists of today? :-)
>> Btw, Tim P, that negative expo CV allowing a single inverting CV 
>> summer is a smart choice. What about the double cap pins in your 
>> suggested pinout? Do they give a better solution than the 
>> cap-to-ground used in both CEM and SSM ICs?
>> /mr
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> -- 
> --Tim Ressel
> Circuit Abbey
> timr at circuitabbey.com
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