Tuesday, August 21, 2012

0.2% THD


Have just made a PCB for Thomas Henry's new VCO based around a OTA & a 555 Timer. It's pretty clean layout without too many links and roared into life immediately. The only issue with the board was i forgot R46 which biases the sawtooth. As it was in the next room I did drag in this Audio Spectrum Analyzer to help adjust the Sinewave purity adjustments and got down to a pleasing 0.2% THD ~ the peak-to-peak amplitude is a bit low for the sinewave compared with the triangle/ramp/pulse so may try tweaking up the input to the OTA by changing R34? Still need to do the 1V/octave adjustment so need to look for that last 2K tempco I have somewhere...

2 comments:

Jack Jackson said...

Hey. Great build. Could you post a schematic or photo of the strip board?

Hotlblack Desiato said...

Hi Jack -- the schematic is in the link from the VCO in the text. The layout will probably be coming along soon...