[sdiy] Digital ADSR - perceivable staircase?

[Jerry Gray-Eskue]

Oh by the way the bit depth of your linear A2D converter gives you your 
dynamic range in db, that is to say each doubling of power ~= 3db and with 8 
bits you can double your power about 8 times Hex 01 to Hex FF so your 
dynamic range is limited 8*3  or about 24 db of dynamic range, a strong case 
for using a log converter after your D2A to extend this range, if you can 
approximate 1/2 db per step you will have a maximum useful dynamic range 
(127.5 db) output with no noticeable steps in output levels. This is only 
true for envelope control, if you are controlling pitch you will get the 
zipper effect.

----- Original Message ----- 
From: "Jerry Gray-Eskue" <jerryge at cableone.net>
To: "Matthew Smith" <matt at smiffytech.com>; "Synth DIY" 
<synth-diy at dropmix.xs4all.nl>
Sent: Tuesday, February 15, 2011 7:40 AM
Subject: Re: [sdiy] Digital ADSR - perceivable staircase?


>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
>>
>> Blog: www.smiffysplace.com  Business: www.smiffytech.com
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