[sdiy] High Q Resonators/digital drums

Thomas Strathmann thomas at pdp7.org
Fri Jun 17 14:28:36 CEST 2011

On 6/17/11 10:38 , Andre Majorel wrote:
> On 2011-06-15 23:30 +0100, Richie Burnett wrote:
>> It's funny how different people hear different differences!  I think
>> the hi-hats are the most innaccurately modelled voice, and sound
>> quite different from the actual TR-808 I recorded.  I wasn't able to
>> measure the frequencies of the 6 free-running pulse oscillators that
>> form the basis of the cymbal sounds in the actual TR-808.
>> Therefore, the DSP model for the cymbals is not as accurate as it
>> could be.  There is quite a variation in sound between different
>> Roland TR-808 machines though, and even a single unit drifts a lot
>> with changes in ambient temperature!
> The most obvious difference is the high-hat. It sounds much
> more forward in the second half. Perhaps the closed high-hat
> colours the perception of the bass drum underneath.

Out of curiousity I listened to the demo again, this time with 
headphones and a signal chain I know pretty well. I still can't honestly 
say that I feel that the hi-hats make all the difference. Perhaps my 
ears are immune to some of the "natural" deviations that occur when you 
compare two units that necessarily suffer from component
tolerances and drift.

> If the TR-808 has op-amp buffers, their limited slew rate might
> make a difference.

Wouldn't low slew-rate amount to low pass filtering (integration) or 
would it be a bad idea to use a first-order lowpass (averaging filter) 
as a first approximation?


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