I am kind of tiered to keep this blog alive and updated. I will still post on my website and on ModWiggler. So for new modules you have to go to my website from now on. Keep soldering,
Every synthesizer enthusiast must have one. A Moog Ladder Filter. There are a lot off implementations out there. So I skipped the breadboard stage and went straight to a PCB. I added two none standard features. A passive temperature compensation and an active compensation for the gain loss when increasing the emphasis. This first PCB was intended to test some parts values and looking for the difference when using LM394 matched pairs vs. ordinary BC550C. Matched and unmatched. I am still in the process on testing the values for the compensation of gain loss with higher emphasis.
As you can see on the picture of the PCB I have made some errors but the are all fixed with some additional wiring. So I can make my tests. As for the LM394 vs: BC550C. There seems no audible difference when using ordinary unmatched BC550C. When testing the BC550C afterwards the were in a very close match right out of the box (same batch). I still have to investigate this more. I’ll keep the PCB for use with both parts. Besides error correction the next run of PCB will include bringing out all filter points to an optional additional board. This intended to bring out the 6dB, 12dB and 18dB outputs.
No schematic to publish yet. I want first to make some more tests for part values and alternative configuration. Before closing here are some screenshots.
The Moog Ladder Filter can be used as a sine oscillator.