[sdiy] That BBD chorus sound. TX7s, DDL chips and CS8420s

Batz Goodfortune batzman at all-electric.com
Sat Aug 17 15:23:10 CEST 2002


Y-ellow all.
         While I'm here and thinking about it, earlier today I came across 
a web site where the person postulated that the unique sound of a BBD in a 
chorus unit was basically down to the minute losses as the voltage is 
passed from one cell to the next along the BBD.

It was actually an argument against BBDs and Pro digital delay lines. 
Citing that a BBD of more than 4096 elements is folly. Noise and wave form 
warpage etc. But suggested that this is the mechanism that colours the 
sound in a BBD and why they are BAAADD.

Where as of course we might say, "I'll put up with the noise because they 
sound so GoooooooD!"

When I thought about it, it almost reminded me of the kinds of processes 
that happen inside valves and leads them to sound good to our ears. But it 
stands to reason that in chorusing or flanging especially -where there's a 
feedback/regeneration thing happening - it would give a less than pure 
result and the colour we've come to love.

Therefore what would be really cool is a digital delay line followed by a 
valve stage. BUT that the valve stage be within the feedback loop etc and 
not just stacked on the end of the final signal. So that the valve process 
is regenerated/cancelled/fedback/etc as if it were a BBD. Except that it 
would theoretically be a crystal clear sound and able to delay for seconds.

I have no plans of doing this of course, I can't even find a DDL chip or a 
small, cheap-assed DDL unit I can use for the TX7 but it could possibly be 
one way of getting the best of both worlds.

But to that end, If anyone knows of a DDL chip (I know there have been 
some.) that might lend it self to 700mS ~ 1000mS, and is obtainable for a 
reasonable price in quantities of 2 or 3, I'd me most interested. I'm also 
after some CS8420s if they're not outrageously expensive and available in 
quantities of 4 or 5.

Thanks in advance.

Be absolutely Icebox.

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