[sdiy] convolution

[Scott Juskiw]

The few times I've seen this done "ala analogue", the basic technique 
used a line of multipliers being fed by dual BBDs. The two input 
signals are fed to the BBDs and each set of tapped outputs feeds a 
multiplier. It sort of looks like a ladder with the BBDs being the 
two long side pieces and each rung of the ladder being a multiplier. 
Correlation is also done in a similar way. The big issues with this 
approach are: it takes a lot of hardware, and it uses BBDs. So is it 
totally analogue? Not really. I was looking at an article in 
Electronotes recently about a convolver/correlator using an big fat 
expensive chip that had dual BBDs and a mess load of multipliers. But 
that chip isn't made anymore.

>i have asked this before ...but i dont know if it made it to the 
>list ... EMU samplers have a effect that they call "transform 
>multiply" ...taken from the E4xt Manual "Transform Multiplication: 
>this function merges two sounds together in a unique way which can 
>create many strange and beautiful sonic textures. Frequencies common 
>to the original sounds are accentuated while uncommon frequencies 
>are discarded"
>
>  it is my understanding that this is called "convolution" and it 
>seems to me that this can be done in the analog realm also. but i am 
>not sure how exactly.
>  thoughts? ideas ? somehow this makes me think of balanced 
>modulation and using multiple balanced modulators to "narrow down" 
>the frequency ranges of the input signals ..