This module is really something else. I came up with the idea of building it since I wanted to include a sync option in my quad LFO. So I googled a little and found a post on Wiggler where this question has already been asked. Yves himself answered, that it’d hard to implement a sync option into that circuit. The reason is the time it needs to get into self-oscillation.
So I asked in a facebook group if anyone has an idea. Someone told me to have a look at the Feague by nlc. Luckily there is a schematic available and I instantly went for it. The sync option, however, acts more like freeze. It stops the oscillation as long as you send a gate signal into it. Just put whatever signal you got into it and you have lots of potential to get awesome sounds out of it!
The module itself is a quad VCO, LFO and VCF. Lots of functionalities in a small package. The 1V/Oct tracking works great over five octaves and is stable too. To achive that, it’s important to match the transistors and to use a 1k tempco, which needs to be thermally connected to the transistors. Use some thermal paste for that and make sure that the paste itself isn’t electrically conductive. Just to avoid a short. If you don’t need precise 1V/Oct tracking just use a normal 1k resistor. You don’t even have to bother about matching the transistors.
The trimpot is used to get the correct 1V/Oct tracking. Just hook the module up to a sequencer or keyboard and play two notes at different octaves. I went for C1 and C4. Now just turn the trimpot until you got it in tune. That’s it!
I used the following stripboard layout for my own build. Here you can download the high resolution stripboard layout and schematic: nlc_feague.pdf
Here are some pictures of my build:
I also want to record some demos of it. So stay tuned!