[sdiy] Triangulation rant!

[Tim Parkhurst]

On 8/21/06, karl dalen <dalenkarl at yahoo.se> wrote:
> Im looking for a very well defined triangulation method, in saw to triangle
> converters the diodes cuses a glitch (even if the diode is made out of a
> trannie)
> wich usually is compensated by a cap, is there any other methods that temp
> variation and amplitude variations and glitch could be kept to an absolute
> minimum?
> Even if i have to go as far as keeping the triangulation cirquit in a oven!
>
> My problem is that i need several separate suboctave triangles, there is
> several
> approaches for this however im looking for near or close to absolute amplitude
> uniformity from  60Hz to 14KHz wich might look trivial but in a deeper look at
> it it's
> not! The symnetry however does not have to be perfect slight leaning is Ok as
> long
> i dont get any glitches or under/over shot's!
>
> Im starting to incline/batter towards an precision saw osc and creating
> suboctave saws and switch them periodically with the aid of a phase
> positionable PW  to generate the triangels and to overcome the glitch
> in the switch for overlapping and cancelling sawtoth's.
> Or by using clamping op amps wich is quite expencive but would
> give top notch performance (wich i dont need, geee)!
>
> What op amps can withstand input clamping without phase reverse?
> ie, lets asume a input voltage of +/-10V and a supply of GND and +15V
> the opamp is supposed to clap the negative portion of the inputssignal!
>
> Any ideas folks?
>
> KD
>

How about a high frequency VCO -> binary up/down counter -> D/A
converter? Easy to make suboctaves and varying the phase is as easy as
resetting the counter. You'll have to tweak the VCO to make it run
properly at 16 or 32x audio, or it might be worth the effort to try
running the saw out into an A/D and use the results to drive the
binary counters (a-la Blacet Miniwave). This way, you can still run
the VCO at audio frequencies. Yes, you have to be a little careful
with your conversions to make sure they're monotonic, and you'll have
to filter the digital outputs, but all of that is (relatively) easy
stuff. The plus side is the control you get over the resulting
triangle waves (tweak the counter circuit a bit and you can get
multiple saw waves too).


Tim (triangle wavey gravy) Servo
-- 
"Imagination is more important than knowledge." - Albert Einstein