[sdiy] saw vs ramp, audible?

[Donald Tillman]

On Dec 9, 2024, at 3:05 AM, Gordonjcp <gordonjcp at gjcp.net> wrote:
> 
> On Sun, Dec 08, 2024 at 02:43:50PM -0800, Donald Tillman wrote:
>> Note that a sawtooth ramping down has all the harmonics in phase with the fundamental.
>> 
>> And a sawtooth ramping up has its harmonics alternating in phase (+1, -1/2, +1/3, -1/4,...) from the fundamental.
>> 
>> So when you want to combine a sawtooth with, say, a square wave, one will make an awful lot more intuitive sense than the other.  This is extremely important to people, like myself, who combine waveforms a lot.  
> 
> So does it make a difference what the phase of the squarewave is when you add it?

Completely.

If you have a traditional VCO, say like on the ARP2600, and you sum the square wave and the ramping-up-sawtooth wave, hoping for something that has heavier odd harmonics, the surprising result is a double frequency sawtooth wave.  "WTF?"

Then someone has to explain that mixing these two classic waveforms, the sawtooth fundamental and odd harmonics are really opposite the polarity of the square wave fundamental and harmonics.  So they cancel, leaving only the even harmonics of the sawtooth.

  -- Don
--
Donald Tillman, Palo Alto, California
https://till.com