Yamaha CS80

As much as I like the sound of the CS-80 Chorus, even the "darkness" 
of it, I was wondering why is sounds *so* dark (low pass filtered), 
compared to your usual BBD-based chorus devices.

All right, you need a anti-aliasing filter and a restauration filter 
for any good BBD-based effect, but usually you only need dramatic low 
pass filtering of *long* delays (echo devices), where you find corner 
frequencies of 5kHz, or even 3kHz, sometimes. But on a chorus, you 
normally get away with "almost" full audio bandwidth; the sound may 
get *slighty* dark, but not much.

I've been curious about what dramatic filtering would go on in the 
CS80 chorus, and what I've seen so far was a big surprise:

* Anti-Aliasing Filter: 16kHz, 2nd order
* Restauration filter: 16kHz, 2nd order

Hey - that's pretty much "full audio bandwidth" !
Even the two combined may result in something like a 12kHz corner 
frequency, and 24dB/Oct slope - not explaining the dark sound at all.

Curiously looking further, I found a combination of 27k shunt 
resistor and 15nF shunt capacitor at the output of each VCA that 
passes the signal from the BBD for panning effects. Together with a 
100k resistor that feeds an opamp summing node from the VCAs, we can 
calculate the corner frequency of the resulting low pass filter 
function:

R = 27k // 100k = 21k 
(The VCA has a current output which doesn't contribute an R)
C = 15n
f = 1 / (2 * Pi * R * C) = 500 Hz

That means, the signal is conditioned for the BBDs with two 16kHz 
filters, only to be filtered with 500 Hz (!) in the VCAs ?!

Very strange. Ok, it's just a one-pole filter (6dB / octave), but 
500Hz is damn low.

Maybe there's a typo in the schemos, and it's 1.5nF capacitors, not 
15nF. Then we'd have a 5kHz LPF instead. But the same "0.015" is 
printed at each of the four capacitors on the four VCAs.

Or is this a deemphase circuit? But I can't spot any preemphase part 
anywhere ...

JH.