More Noise...

Well arced up the Frequency Counter and the Spectrum Analyser and had a bit of a play. The Linearity of Oscillator is pretty good as you can see that over a 10V range it is very close to a straight line -- especially for a couple of transistors that weren't even matched! The lowest frequency response is pretty close to pink and the other two show the increasing frequency response. You can see the lower level amplitude fall as the energy gets spread over a larger frequency range. The picket fence effect is, I think, due to the output being a square wave -- it is well outside the hearing range of most people anyway...

Random Success

Had some success with this board. I layed out a PCB for one of the modules in Thomas Henry's A Synthesizer for the 21st Century. This is the the Voltage Controlled Noise Source. I may put up the PCB layout but it isn't the most compact. It also didn't come out quite as well as I had hoped as the ground plane pour was too tight on the tracks. Anyway about half an hour with the Oscilliscope and a bit of head scratching tracked down the shorts and it is all working well now even if it isn't the most attractive of boards! I think that maybe turning the CMOS devices through 90 degrees might make a more compact board... I have already changed this layout to make the log converter a bit more accurate with some spare LM394's I have got so I may persist... Will try and post some pictures from the Spectrum Analyser tomorrow for some academic interest...

That's Better!

This PCB went a bit better! Cleaning the board with Acetone certainly helped... Will do a bit of experimentation with this once it is working as it is a bit of a different configuration from the OTA and ladder filters...

Acid Adventures...

Have done a few layouts recently. The actual laying out has gone well but the etching has failed as I have had a bit of trouble getting Amonium Persulphate as easily as I used to so I tried Hydrocloric Acid and some Hydrogen Peroxide mix. The problem is that it is etching the toner off the board before it is completing...

32 Years Later...

I remember buying this Elektor and always being interested in the Resonant Filter Module. Well here we go! I just need to attach it to the front panel from the last post!