Hey guys, been using Pd for a few months now, and I'm currently working on a project to emulate the Casio Mt-40 keyboard but am having problems with aliasing.

The main voice of the keyboard consists of two 16 step square waves that are added together then have envelopes and filters applied. I'm currently using tabread~ to cycle through these waves which I have saved in arrays, this sounds great at lower frequencies and almost exactly like the original! The problem is that higher pitched timbres such as the Celesta sound horribly aliased.

I've tried upsampling the part of the patch which contains the wave tables, but this still leaves distortion of some kind. I've heard that tabread4~ will give me less distortion, but this removes any crispness of the sound. Should I increase the size of the wavetables and used tabread4~? Or have I screwed up the upsampling somehow?

I'm including a rough version of the patch, the wavetables are inside the Waves~ abstraction. Any help would be hugely appreciated!

Jared

http://www.pdpatchrepo.info/hurleur/MT40wip.zip

I don't have time to look at your patch right now, but the oversampling and filter should be where the table reading takes place, not where the tables actually are.

And, yes, [tabread4~] is typically a better option because not only does no interpolation result in some distortion, those new frequencies from the distortion can also alias. However, I doubt it would really be all that significant for a square wave. If you can really hear the difference, then I would think that the tables are too small.