On Tue, 10 Dec 2013, Daniel Forró wrote:
Thanks a lot, Martin, you did great job! That's missing and very
important addition to Owner's manual. How you could measure Hz values
with such precision?
Hi,
let me explain:
- Very low frequencies where measured by measuring the time of a cycle in
a wave editor or with a stopwatch.
- Normal low frequencies where measured simply by counting the number
of "beats" in a certain timespan (one minute for example)
- Higher frequencies where measured using a wave editor and viewing the
starting points of the cycles.
- In the case of for example the FB01 I have reverse-engineered a formula
that produced a table that (almost) matched my measurements.
LFO_freq_Hz = 48. * (2 ^ (1. / 16.)) ^ (i - 250)
the number '48' was the frequency I measured for i=250, where i is in the
range 0 to 255 (8 bits).
(If anyone can reverse-engineer a similar formula for the DX7, DX11, etc:
that would be nice so let us know!)
- Missing values where calculated using interpolation and extrapolation
- The precision that my tablevalues suggest is probably higher than the
real precision.
- As extra study material I used a specification doc for one of the Yamaha
FM chips (google seacrh for ym2151synthesis.pdf) that contained a table
with values. I have attached a page from this document to this mail.
MT
