[sdiy] reverb mad from multiple delays

[Steve Lenham]

> I recently built a digital delay based on the Buchla 288. It has 8 
> equally spaced delays, with individual outputs and sliders on the  front 
> panel. Some of the sounds I can get from this got me thinking  about 
> hardware reverb. I know that there was the 3011 BBD that was  used to make 
> reverb, but I think it could be done much better with  digital techniques 
> (of course I mean hardware digital, not the  sensible DSP/micro solution 
> ;).
<snip>
> Does anyone have experience doing this and/or have documents from the  old 
> studio units that did it? I'm thinking it would help immensely to  see 
> schematics for the EMT 250, Eventide SP2016, AMS RMX and whatever  other 
> reverb units were being made before everything went software...
>
> Mark

Hi Mark,

I do a lot of work on Lexicon 224/224X reverbs and even then (1979 or so) 
they were using the "sensible DSP/micro solution". It's just that they built 
their own DSP out of discrete TTL logic (LS or S series). As a result the 
224s "DSP" occupies three big Multibus I cards and something in the region 
of 150 individual ICs!

(see card pics at http://www.bendensound.co.uk/lexicon224p1.html)

The DSP program memory (128 instructions per sample, IIRC) is loaded by an 
8088-based single-board computer on yet another large card.

Have a look at the Spin Semiconductor FV-1 (http://www.spinsemi.com/) too. 
It's essentially a DSP optimised for audio effects, with built-in ADC/DAC 
and delay memory. Even if you choose a more discrete solution, there is the 
source code for a lot of algorithms freely available on the website, giving 
useful pointers as to how various effects are implemented.

BTW, if you find EMT, AMS or Eventide schematics then I'd love to see 
them...

HTH,

Steve L.