But, back to the beginning. After my last post, I received an interesting comment by "terjewinther" from the Polysix Yahoo Group. He suggested that the calibration can have a strong effect on the sound of the synth. So, I opened her up again, brought out the multi-meter and oscilloscope, and started in on the calibration procedure as listed in the Service Manual. I made it through the filter tuning including offset, filter frequency, resonance, and EG intensity. What I found was that my DAC was a bit off and my EG intensity was way off. My filter cutoff and resonance were pretty close, but there was some variation from voice to voice. So, I'd say that the biggest impact of the calibration was to make the 6 voices more consistent with each other, especially at higher resonance settings.
After completing this portion of the calibration (I stopped just before the calibration of the Keyboard Tracking), I closed the lid, plugged in the audio recorder, and took some new measurements of the trusty sawtooth wave. Did I smooth out the high end harshness??? Did I get rid of that weird bump that I was seeing around 7 kHz???
Well, the graph below has the answer....and the answer is "no". There appears to be no change in the frequency response. I doubt, therefore, that the calibration got rid of the harshness. (Sure, when I play with the synth over the next few days, my ears will tell me things that this graph can't...but you can't really trust your own initial impression because we humans are so easily prey to confirmation bias...hence, objective measures are best for immediate trouble-shooting and feedback).
|Frequency Response After Following the Tune-Up Procedure in the Service Manual|