Filter: waveform



At VEKTOR MK II rev 6 I have DC-coupled the input amplifier to the two internal clipping amplifiers which takes the clippers off of the virtual ground circuit. High-pitch oscillations have been eliminated. Clean and dirty input amplifiers are now separate and two levels of input-clipping (compression) have been added to the dirty end. The input amplifiers are now based on the OPA2134 while the high-gain clippers are based on the wide-swinging TLC2272. I was hoping to get away with a 5532 in there…doesn’t cut it…NEED the swing.

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I have a capture from my scope here that shows the output of the buffer transistor immediately after the clipping section on one of the VEKTOR Mk II channels.  The blue trace is the input to the circuit being generated by my bass as a sustaining E on the 1st string with the tone turned down to emphasize that nice fundamental sine-wave.  The yellow trace is the output of the not-starved buffer transistor on the symmetrical channel.


Here the is the same scenario (I am playing a lower note) but after the tone contour section in the same amplifier channel.  You can see how the tone contour circuit distorts the signal as it emphasizes certain frequencies by bypassing others.  Notice that the distorted output waveform shows a higher frequency content than the input waveform: this is a visual demonstration of clipping harmonics in an audio signal.  It shows how hard transitions in signal voltage can introduce higher frequency information into the signal.

You can also clearly see the fundamental under those partial spikes.  This particular distortion shape is tracked flawlessly by my 3Leaf Audio Octabvre.  Concerning guitar and bass distortion, this is octave food.

I’m working on massaging the noise floor and fine tuning the gain steps.  VEKTOR will never be totally quiet at high distortion ratios but I would like to minimize noise for gentle-effect usage on the left half of the ratio (blend) control.  I’m also concerned about noisy power supplies.

Read: A Musical Distortion Primer