[sdiy] 4046 VCO

[Tom Wiltshire]

I did some experiments using the 4046 as a high frequency oscillator and found that chips from different manufacturers varied enormously. Even chips for the *same* manufacturer varied quite a bit from one to another. I had to tweak the values of several components around the 4046 to get the same range from different chips - the kind of individual tuning I hate!

The point to remember is that the VCO in the 4046 was designed to be used in a closed loop, so accuracy in terms of a specific output at a specific input wasn’t really necessary. The feedback would sort it out.

My experiments are documented here, if you’re interested:

https://electricdruid.net/adventures-in-top-octave-generation/

==================
       Electric Druid
Synth & Stompbox DIY
==================

> On 6 Jul 2018, at 00:45, synthCube <info at synthcube.com> wrote:
> 
> Probably... the Fonik 4046 is ic - dependent as well as a couple of other 4046 based designs we carry here...  will be interesting to learn from others about technical spec differences if any, or something not documented 
> 
> Sent from my iPhone
> 
>> On Jul 5, 2018, at 5:20 PM, Tim Ressel <timr at circuitabbey.com> wrote:
>> 
>> Hiya,
>> 
>> So I built up a Thomas Henry 4046 VCO and ran into an issue: the frequency out is way too high, starting at 55KHz and going up to 175KHz. I checked my schematic and it all looks good except for one thing; I am using a 74HC4046 instead of a CD4046. Is that causing my problem?
>> 
>> -- 
>> --Tim Ressel
>> Circuit Abbey
>> timr at circuitabbey.com
>> 
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