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.
The BOM requires:
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
and
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.
NLC words of wisdom
I like to get the ICs on first.
I'm using PCB version 2, so some mods are needed.
Had to cut one trace and add two resistors (10k & 2.2M).
Be careful not to short anything ... its a bit tricky
Q1. Its a PNP/PNP matched double trannie.
I used a microscope to find the dot that helps orientate it. But if your eyes are better than mine you could do without the scope.
The 1K tempco resistor.
INSTAL headers. theyconnect the two PCBs.
Links
* NLC Blog
* Build notes
* Electro-music (Ian Fritz)
* Modularsynthesis.com
* mUFFwiggler
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