Makes sense, thanks! Having not dug into it, when I look at VCOs I’m not sure what features (or lack of features) are due to the chip and whats simply added or omitted by whoever is making the rest of the design.
Not sure how to multiquote and tag BlackDeath here but
direct sine wave output (no filtering circuitry required)… 3340’s also don’t have easy “through-zero” FM, meaning FM sounds aren’t very musical as they don’t stay in tune.
Is there much of a difference between shaping a triangle, like the AI Synthesis oscillator and a ‘true’ sine wave? I do like to use my sine wave lots, so if theres a “better” option out there that would be good to know for future builds! And thanks for the quick description on through zero FM - it’s something I keep coming across and meaning to look up but haven’t gotten around to.
Just highlight what you want to quote and click the “Quote” thing that appears above what you highlighted.
And then put your response outside the [quote]…[/quote] pair.
You can do that multiple times with multiple quoted messages in the same reply.
Depends on how you shape the triangle… it’s always an approximation, and accuracy varies. And how much people care varies, too. (Hm, five consecutive words beginning with “a”. May be a personal record.)
I’m not super picky, but it does end up sounding a bit different because filters aren’t perfect, and more importantly it means I have to use a module since I don’t have a pure sin generator.
Im not convinced the SSI chip can do TZFM with a sinewave carrier as this is generated by an onboard triangle to sine waveshaper. I am yet to get this to a breadboard to see how this works.
Here’s a CD40106 based dual oscillator that looks pretty interesting. The designer acknowledges it has some imperfections but to some extent they presumably could be reduced or eliminated with some design modifications.
Nice find. I’ve got a reverb tank here (I think the same one he has) that I couldn’t get driven properly, looks like I’ve got something to work from now.
Per wikipedia “the thermal coefficient of electrical circuit parts is sometimes specified as ppm/°C, or ppm/K”, so I assume that the K that I see in the listings refers to ppm/K.
I am referring to the video that uses a 2.2k NTC thermistor, not a tempco. I have given up looking for special tempco resistors as they come at ridiculous prices if one calculates the shipping from the few places abroad that sell them. Not worth paying 2x the price of an AS3340 IC that I can order locally. I think. But I might try a simple circuit that uses a thermistor that I can get locally for less than 50c to see if it’s any good.
I’ve been looking for a solution to a similar problem. I’m going to build the th555 vco but it calls for the same thermistor. I have ordered some 2k ptc thermistors but I don’t know the ppm rating. I lack the knowledge of how to implement the ntc in it’s stead like in the video to which you refer.
If you want to try and wade through this document you can learn more than you really need to know about temperature compensation in exponential converters:
I just finished my first Thomas Henry 555vco on strip board. I used the build guide from Eddy Bergman’s diy synth page Eddy Bergman.com: Synthesizer Build part-37: THOMAS HENRY VCO-555.
The vco sounds incredible. I have it calibrated to volt per octave across like 5 octaves so far. It stays in tune with my 3340 pair. I haven’t installed the ptc thermistor but it still performs quite well for my needs. The hard sync is BANANAS! I’m blown away. Thanks to Thomas Henry for sure and @EddyBergman for the build guide and taking the time to answer my questions. Construction on number 2 starts this weekend. I’m impatient to test these hard synced to each other…
