[sdiy] Digital ADSR - perceivable staircase?

[Tom Wiltshire]

Jerry makes a good point too.

I'd forgotten, but the worst trouble I had with stepping was on the LFO's 'spike' wave, because it had the steepest waveform. If you're using a exponential  curve for the envelope output, the steep section will jump many steps at once (eg DAC value jumps from 4 to 56, not from 4 to 5). This makes the problem much worse. My Ramp and Sine LFO waveforms were fine because there were no steep slopes on them. The spike was a problem becuas eit curved up and down abruptly.

T.

On 15 Feb 2011, at 13:40, Jerry Gray-Eskue wrote:

> I think it is more an issue of how large the step is. Humans are very sensitive to Pitch changes, but much less sensitive to Volume changes.
> 
> Basically we use db ( decibel ) because it is the smallest unit (ratio) of change we can commonly perceive as a volume difference. This ratio from one power level to one db up is about 1.122.
> 
> So if you are using a liner D2A converter you will have large db changes in the first few steps
> D2A value from 1 to 2 ~= 3db (2*the level ~= 3db)
> By the time you get to D2A value from 9 to 10 you should be running under 1db per step.
> 
> 
> ----- Original Message ----- From: "Matthew Smith" <matt at smiffytech.com>
> To: "Synth DIY" <synth-diy at dropmix.xs4all.nl>
> Sent: Tuesday, February 15, 2011 12:12 AM
> Subject: [sdiy] Digital ADSR - perceivable staircase?
> 
> 
>> If we consider a digitally-generated attack signal as a staircase, at what 'width' of step - in other words the time between increments in level - would the increase in volume of the system output become noticeable?
>> 
>> So as to have something to go on, I am considering a maximum A/D/R time of 2 seconds so, at maximum time, a 'step' would be about 8ms long, based on 256 levels x 256 steps.
>> 
>> Really wondering what my maximum time can be before the 256 steps become obvious.
>> 
>> 
>> -- 
>> Matthew Smith
>> 
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