[sdiy] FW: Kawai K3 - Bandlimited Waveforms

[karl dalen]

Do the PPG realy use a variable clock as you have drawn?
Are the variable clock a phase acc from wich PPG has taken
the msb to clock the counters with?
http://www.electricdruid.com/index.php?page=info.wavetableoscs

KD

--- Den mån 2010-01-18 skrev Tom Wiltshire <tom at electricdruid.net>:

> Från: Tom Wiltshire <tom at electricdruid.net>
> Ämne: Re: [sdiy] FW: Kawai K3 - Bandlimited Waveforms
> Till: "karl dalen" <dalenkarl at yahoo.se>
> Kopia: synth-diy at dropmix.xs4all.nl
> Datum: måndag 18 januari 2010 03.53
> 
> On 17 Jan 2010, at 22:34, karl dalen wrote:
> 
> > Its interesting to note that the K3 does a poor job in
> this
> > sample table per octave switching, one can very easily
> hear
> > when a table are swapped in and out.
> 
> They didn't use any interpolation between adjacent
> wavetables then.
> As we've already discussed, they did interpolate between
> wavetable samples, but it looks like that was it.
> 
> > Btw, should phase accumulator NCO's be wieved as
> > variable sample rate or fixed rate NCO's?
> > 
> > I was thinking of the aliasing on an NCO using low
> rate
> > versus one that uses a high rate (1Mhz or more).
> 
> Well, this is where the confusion arises.
> 
> I'd say (and this is an opinion not a statement of fact)
> that if it's got a "high" sample rate and "small" tables,
> then it can be viewed as a variable sample rate system. At
> least, it approximates one. This is the PPG scheme. In a
> system like this, each individual wavetable sample is
> typically repeated many times, which is roughly equivalent
> to clocking the samples out at a much slower, variable rate.
> In practice, the line blurs, since at the top of the PPG's
> range, it starts missing samples out because the sample rate
> isn't high enough (only 250KHz).
> 
> Obviously the reality is that both systems have a fixed
> rate, and it's purely a way of viewing it.
> 
> T.
> 
> 


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