VCO testing

A project log for VGA VIDEO SYNTH

vga analog video synth

JulienJulien 03/28/2018 at 12:500 Comments

the vco is working fine minus two non-lethal errors.

I wanted to have a sine and triangle outputs. The sine output was supposed to be shaped after the triangle in the regular synth fashion, with a diode clipper.

However the output of the XR2206 is amplitude modulated (PIN1 of the chip) and therefore the amplitude coming into the sineshaper is also modulated. The Sine wave will be only obtained with full amplitude where the diodes are about to conduct. Not ideal, although could be interesting to have a morphing wave (triangle - sine - square).

I went back to the datasheet exemple with a Sine/Triangle switch. The advantages of this configuration are a less busy front panel and two op-amps removed (less $$$ on the shopping list). The protoarea on the board was a good idea.

I hate trimmers.