Analog reverb

[EricKnabe]

Since digital reverb algorithms involve running several different delay times and feedback settings, wouldn't it technically be possible to run several BBDs in parallel with various settings to achieve an analog reverb pedal?

[Fancy Lime]

Since digital reverb algorithms involve running several different delay times and feedback settings, wouldn't it technically be possible to run several BBDs in parallel with various settings to achieve an analog reverb pedal?

Yes. Yes, it would. And it has been done (don't ask me pedal names). But it is just not really practical. To achieve a reverb that can hold a candle to even a simple first-generation digital delay (and those were not exactly fantastic), you need at the very least two, better three BBDs with multiple taps (which were never cheap or easy to get and are almost completely unobtainable today) plus all the periphery of multiple clocks, drivers etc. Or more BBDs without multi tap. It is technically possible, but it has never been commercially viable. And it does not seem like many DIYers have thought it worth their time.

Cheers,
Andy

[EricKnabe]

Makes sense, thanks.

[Mark Hammer]

The MN3011 and MN3214 were both originally developed for the precise purpose you describe.   The 3011 had 6 different "taps" after harmonically unrelated numbers of stages, and the 3214 had 5 taps.

Those circuits I've seen that used the 3011 for "analog reverb" tended not to employ them very well, and the result was that such pedals did not sell very well.  At the same time, digital started to get much better and much cheaper.

While, in theory, one can run multiple BBDs in parallel or in some series/parallel combinations, to mimic reverb, the different clock frequencies they would need to be run at, in order to achieve variations in delay times, runs the risk of what is referred o as "heterodyning", a sort of ring-modulator summing and differencing of clocks that shows up as noise.  It can be overcome, but necessitates careful layout and often a more complex circuit, over and above the complexity of multiple BBDs driven by multiple clocks. 

The Boss Dimension-C uses two BBDs that are counterswept by a common LFO.  So as the LFO makes one clock sweep higher, it makes the other BBD clock sweep lower.  The unit uses two compander chips in order to keep the noise level manageable, even though few single-BBD/single-clock choruses use even one compander chip.

So, it's a good idea, in theory, but probably a whole lot easier and more successful to get a Belton brick or use and FV-1.