Thomas Henry's MIDI-to-CV Connection

[Jeroen Proveniers]

> -----Original Message-----
> From: WeAreAs1 at aol.com [mailto:WeAreAs1 at aol.com]
> Sent: Friday, August 18, 2000 12:01 PM
> To: kirke at lmi.net; synth-diy at node12b53.a2000.nl
> Subject: Re: Thomas Henry's MIDI-to-CV Connection
> 
> 
> In a message dated 8/17/00 10:06:27 PM Pacific Daylight Time, 
> kirke at lmi.net 
> writes:
> 
> << I'm curious. What do you consider to be limitations
>  of a software lfo? >>
> 
> 1.  Inability to accurately trace LFO waveform at fast LFO 
> rates (approaching 
> audio and above).

Depends on sampling rate. Why could a LFO not be accurate and an audio osc
does?

> 2.  Stepping noise/artifacts. (apparent mostly at slow rates - see #3)

If you use 8 bits yes, but at 12 bits or more you can't tell the difference.
If I change 1 lsb each second of a DAC, will you hear the difference? Can
you hear that the filter cutoff is now 2-4 Hz lower?

> 3.  Limited low frequency range (analog LFO's can cycle over 
> several minutes 
> or more - see #2)

Can be as slow as you want, if you want a few years. But ok, 1 lsb change
each day or so.

> 4.  Inadequate resolution of frequency control. (analog = 
> infinite freq. 
> resolution)

Can be very high. Just depends on how you write the software. But do you
want to control the freq down to 1/10000th Hz? Do you care if the sweep
takes 1 minute or 1 minute and 205.56us? Analog will certainly drift more.
Especially with long time stability is a problem, and temperature-dependent.

> 5.  Software LFO's take up precious processing resources, 
> sometimes causing 
> increased latency in other necessary processes (especailly at 
> high LFO rates)

Hmmm, what you state here is also valid for just plain audio osc. It more a
matter of well design practices.

I'm currently working on project with digital LFOs. I'll see what problems
come across. Maybe i'm wrong. -:

JJ