[sdiy] [synth-diy] numerically controlled superoscillator without hard sync

[cheater00 .]

On Mon, Feb 10, 2014 at 2:03 AM, Tom Wiltshire <tom at electricdruid.net> wrote:

> How are you going to generate the IRQs or DMA clock without it being synchronous? Do you feed them in from VCOs outside?

Yes!

> I get the idea of using buffers in one decent DSP and then feeding the samples out at different rates, but I'm worried about the sample rates being synchronous - that'd rather miss the point.

It all depends what the time resolution is of the DMA responding to an
external signal. If the DMA will get triggered at most 100 times per
second, we'll definitely hear a lot of that in the output. If it gets
triggered 100 million times per second, we won't.

> Richie is right about DDS chips being probably the best way to do the "VCO" part - they'll handle the frequencies we're taking about and the resolution is extremely fine. You'd need to send them lots of data to make smooth slides or modulations, but that's not impossible.

What did you think of the numerically-controlled oscillator post from December?
It's basically DCO, but it works without hard-sync - instead it uses a
counter in a control loop fed back into the pitch CV.


Cheers,
D.