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...

3 comments:

Unknown 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...

Jim Read said...

Hello Mr Forbin,

Hope you and yours are all OK and not affected by the floods.

I made Eddy Bergman's strip board layout and failed. I found single sided pcb's for TH VCO-1, Xr2206 and X4046 but haven't been able to find one for the VCO-555.

I wondered if your PCB layout was available or if not would you be able to point me in the direction of another one.

Kind regards - Jim