Design of VCFs

[John Pisani]

I am designing and building a vcf and I am having trouble obtaining a
large range for my cutoff frequency. The cutoff frequency only ranges from
about 300 Hz to 3000 Hz.  I would like to get it lower to about 20 Hz and
higher to about 15 - 20 KHz.
My circuit consists of a JFET for variable resistance, an opamp and some
resistors and caps.  Any suggestions?  DOes anybody know of any interenet
sites that have schematics for other vcfs?

Thanks,
John Pisani