[sdiy] Variable-rate drum sample playback

[rburnett at richieburnett.co.uk]

u-law is equivalent to logarithmically spaced quantisation levels at the 
ADC/DAC stages.  It is something that is applied on a per sample basis 
to the waveform when being recorded and played back.

This is different to the "compress the hell out of the recording and 
then apply the envelope again at playback time" approach that Roland 
used.

Both are techniques used to squeeze more dynamic range out of low 
bit-depth samples.

-Richie,



On 2018-06-26 11:34, mark verbos wrote:
> I’m still a little confused on this whole µ-Law DAC thing. Is it the
> same net effect as the "DAC followed by VCA swept by the data lines"
> system that the 909 cymbals used?
> Couldn’t you do that too? (not that there’s anything wrong with what
> you’ve done)
> 
> 
> Mark
> 
> 
>> On Jun 25, 2018, at 11:06 AM, Tom Wiltshire <tom at electricdruid.net> 
>> wrote:
>> 
>> There was a discussion recently about drum sample playback that got me 
>> inspired to have a play with it. I was asking about the u-Law DAC here 
>> as well, but in the end, I didn’t bother, at least not yet. I wrote up 
>> my experiment on my website:
>> 
>> https://electricdruid.net/experiments-with-variable-rate-drum-sample-playback/
>> 
>> What I found quite cool was that it’s possible to get three separate 
>> samples *each with their own variable sample rate* into a single PIC. 
>> That’s not half bad!
>> That’s using 4K samples and a 16K chip (so three samples leaves 4K for 
>> code). That means the 8K samples for things like the Ride cymbal would 
>> probably need a chip of their own - but still, you can wrap up the 
>> sample memory, the DAC, and the VCO that clocks it all onto a single 
>> chip.
>> 
>> Hope you like it. I don’t know whether I’ll take the experiment any 
>> further - maybe one day.
>> 
>> Tom
>> 
>> ==================
>>       Electric Druid
>> Synth & Stompbox DIY
>> ==================
>> 
>> 
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