SpecDrum programming information

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uglifruit
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Re: SpecDrum programming information

Post by uglifruit »

That'd make sense (lower 6 bits of a byte, but being stored as bytes). So the ideal workflow would be making new samples for encoding, then dithering to 6bits (or 7bits in the case of kick drum), then padding to 8bits. (I'm not sure what audio software can dither to arbritrary bit depths, but presumably it's possible with something).
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djnzx48
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Re: SpecDrum programming information

Post by djnzx48 »

There are a few bitcrusher plugins that support arbitrary bit depths with dithering. But it wouldn't be necessary here - the samples are still 8-bit, they just have their volume levels reduced. All it would require is normalising the sample to -6dB or -12dB before exporting to 8-bit.
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Re: SpecDrum programming information

Post by pianomatt »

So looking at the samples in a hex editor it doesn't look like the samples are limited to a 6 bit or 7 bit range. The highest peak I could see in the clap sample was -49, but the kick peaks at -51. 7 bit unsigned is -64 to 63, so while the kick is in range the clap is not - and the snare isn't far off either by the looks of things. I wonder where the author got his information?
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Re: SpecDrum programming information

Post by pianomatt »

I've done a bit of a write-up on my blog of what I did and how I did it, and there are links at the bottom to the TZX and the raw blocks it contains in case anyone wants to use them as a template to make their own.

Loading your own samples into the Cheetah SpecDrum
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djnzx48
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Re: SpecDrum programming information

Post by djnzx48 »

Hmm, very interesting! You're right, I can't find any other sources mentioning the samples being only 6 bit. I'll have another look at those samples.
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Re: SpecDrum programming information

Post by pianomatt »

I've emailed the author to ask how he got those numbers. If he replies I'll follow up here.
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uglifruit
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Re: SpecDrum programming information

Post by uglifruit »

I've checked his book, but that chapter doesn't seem to have any obvious references to say where that info came from.
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pianomatt
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Re: SpecDrum programming information

Post by pianomatt »

It might be from a magazine at the time, maybe misremembered? Then again he might mean something completely different. Either way I'm interested to hear from him because on his website he talks about using the SpecDrum in the early 90s for some demos.
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Re: SpecDrum programming information

Post by pianomatt »

I got a reply from Simon Goodwin, and I'll post more details once I get a chance to reply to him.

Long story short - the 7 bit kick and 6 bit samples isn't entirely accurate, but it is an ideal way of handling the samples because if you keep the volume lower on the other two groups it means you can have a nice loud kick that will cut through the mix without clipping or rolling over.

Also, I made another kit - this time it's an 808.

Demo
Kit TZX
Song TZX
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Re: SpecDrum programming information

Post by matalog »

I took an interest in the Specdrum a few years ago and made my own beatboxing Specdrum kit. I got all of the information I needed from Crash magazines, written by Simon back in the day. I got in touch with him and he sent me some related software to backup.

Out of interest, have you seen the Specdrum System II tape software? It allows proper live playing of all drums at one time, with 8 keys. It adds a slightly different twist to the Specdrum.

Yeah, the drums are basically suitable volumes to be played in their allowed combinations. Looking at the figures in the original samples hex, the range goes from around -50 to +50, with the bass not being much louder than the rest of them to be honest.

Are you still using your Specdrum?

Have you seen this http://www.thesadsongco.com/blog.php?blog_id=18 Search for Specdrum in the blog page.
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