[sdiy] Prophet VS a phase accumulator design

[Scott Nordlund]

> Speaking of reverbs, could be an interesting topic, i have an old ART verb

What model is it? The only one I've heard (Multiverb Alpha or something) sounded terrible.

> with two Z80 seemingly running in parallel, on takes top byte other low byte and a discreete logic wich these two runs into wheter the logic
> does the actuall computation, i guess it do, some kind of spedy MAC
> and Dram but unsure its a 16 bit stereo device, multiplexed PCM54.

Well the Wersi reverb does everything with the 6809. I haven't heard it so I don't know how much it actually resembles "reverb" (versus just delay). But it's mono with 4 kHz bandwidth and 1kwords of RAM (so total delay time maybe 100ms), if that's any indication. Obviously none of the good units did anything like that- most used some sort of discrete logic DSP thing for fast MAC operations, maybe interpolation and automatic address calculation too. Some used low resolution multiplies or even just bit shifts. I've been designing reverbs lately and reverse engineering them from impulse responses (time invariant models only, obviously), which is kind of helpful since there are still a lot of novel algorithms out there that remain unpublished and unknown.

> I will have a look into some of the Dittmar patents anyway.

They're nothing amazing. You could pull up some random yamaha patent and find something more exciting.

> Looking forward to the write up i your going to publish it.

Yeah, I need to go back to working on it. I have all the info, it's just disorganized. It should attract a decent amount of attention.