[sdiy] Digital ADSR - perceivable staircase?

[Jerry Gray-Eskue]

Hmm, it looks like I got a little confused:

ref: http://www.astralsound.com/the_decibel.htm
For power (e.g. watts)

. Multiply your reference value by 10^(n/10).

For pressure (e.g. volts, sound pressure)

. Multiply your reference value by 10^(n/20).

Apparently in this case we should use 6.02 * the number of bits for the 
dynamic range, that makes the 8 bit converter a 48 db dynamic range not the 
24db I stated below.



----- Original Message ----- 
From: "Jerry Gray-Eskue" <jerryge at cableone.net>
To: "Jerry Gray-Eskue" <jerryge at cableone.net>; "Matthew Smith" 
<matt at smiffytech.com>; "Synth DIY" <synth-diy at dropmix.xs4all.nl>
Sent: Tuesday, February 15, 2011 8:05 AM
Subject: Re: [sdiy] Digital ADSR - perceivable staircase?


> 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
>>> www.linkedin.com/in/smiffy  www.flickr.com/photos/msmiffy
>>> twitter.com/smiffy
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>>
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>