Checkout electronotes EN #75.
It's a thru zero VCO that uses analogue switches (DG202) rather than FW rectifiers.
Should be easy to use; LEDs indicate when it crosses zero.
My understanding of the through-zero concept is that with a regular VCO, if the frequency modulation reaches or goes below 0, you won't hear anything. With a thru zero VCO, you'll hear "negative" frequencies.
"The negative-frequency version of a waveform is simply a time-reversed replica of the original waveform". (Ian Fritz. 2009)
Check out Dave Brown's scope shots on his site (Modularsynthesis.com)
of the Ian Fritz "teezer" Thru-Zero VCO
They explain the concept so well.
a S1JL rectifier
Mouser No: 821-S1JL
and a JFET
Mouser No: 512-MMBFJ108
Both have a long backorder wait at mouser.
So possible replacements are:
mouser no: 771-PMBFJ108-T/R for the JFET
Mouser Part No: 583-FM4005-T for the recitfier.
The rectifier is polarized. The cathode end is marked with a band.
On the PCB, I think Andrew has marked the cathode with a dot.
Had to cut one trace and add two resistors (10k & 2.2M).
Be careful not to short anything ... its a bit tricky
* NLC Blog
* Build notes
* Electro-music (Ian Fritz)
To be continued