> I was thinking, there should be space for a jack, so why not make it
> so that the slew circuit could be used, so why not You always need
> another slew limiter!

The "low pass" in the A-196 is not a standard passive low pass
(resistor+capacitor) but a "low pass with offset" as recommended in the
74HC4046 data sheet for this application. It does not behave like a standard
6dB low pass or slew limiter. For details please refer to the 74HC4046 data
sheet (e.g. www.nxp.com/acrobat_download/datasheets/74HC_HCT4046A_CNV_2.pdf
page 6 and 27)

Best wishes
Dieter Doepfer