[sdiy] E-Drum antics, EPROM data dumping

[WeAreAs1 at aol.com]

In a message dated 9/17/04 4:20:45 PM, jmahoney at gate.net writes:

<< The data format? I'd *guess* that it's 8-bit uncompressed digital

audio. (Hmmm... linear or exponential conversion?) >>

What type of DAC does it have?  That would tell us if the audio data is 
linear or was exponentially converted.  The LinnDrum and the Oberheim DX and DMX 
drum machines had exponential data in their sound ROMs, and the DACs in those 
machines were designed to re-linearize the data upon playback.  This type of 
exponential codec is good with crappy 8-bit audio, since the conversion 
concentrates most of the bits on the lower-level parts of the signal.  This makes the 
decays sound cleaner than straight 8-bit linear audio.

BTW, Tom Erbe's "Soundhack', a great audio processing program for the Mac, 
will allow you to load in raw hex text files, and will attempt to turn it into 
editable audio in several standard digital audio formats.  This would probably 
work with the data that you extract from those ROMs.  I think there's a free 
version of Soundhack that you can download, but I'm not sure if the free 
version has the hex/text reading feature.

Michael Bacich