31 May
2009
31 May
'09
3:21 p.m.
On Sun, May 31, 2009 at 03:29:42PM +0200, Martin Homuth-Rosemann wrote:
I'm just working on this problem. It clicks
because I switch the signals on/off
without every smoothing at random moments of the sine wave. I've changed the
timing to switch at zero crossings and the clicks go away.
Looking at the schematics there is no evidence of any
'click removal' action. Also the waveforms summed there
(for 4',8' and 16') would not be sinewaves. Each divider
output has an RC lowpass filter before going to the mix
bus. Assuming the dividers generate square waves, the
smoothest waveform you can get would be a triangular one.
What each of these RC filters does exactly will depend on
the impedance it sees on the mix bus, and this is a complex
function of the drawbar positions (*all* of them for each
bus, since they share the resistors) and the number of
notes already on. If the drawbar for a mix bus is at a
low setting, or at maximum, its impedance would be quite
low (the top end is feeding a virtual ground), in that case
the RC filter frequency moves up, and there is a *highpass*
action from the series capacitor and the mix bus impedance.
This impedance reaches a maximum of around 5k for the third
highest position. If two drawbars are the same position
their corresponding mix busses are even shorted to each
other. So just adding the contributions from each note does
not correspond to what's happening here, both the amplitudes
and the filtering of each note depend on almost the complete
state of the instrument.
Ciao,
--
FA
Io lo dico sempre: l'Italia รจ troppo stretta e lunga.