[sdiy] Frequency modulation vs Phase mod, was: Buchla 295 10-band comb filter topology

[Ingo Debus]

> Am 27.11.2022 um 00:30 schrieb Ian Fritz via Synth-diy <synth-diy at synth-diy.org>:
> 
> Does the DX7 waveform change with keyboard pitch or not? I’ve asked this question before but never got an answer.

So here we go. I measured the output of my DX7, for all six C keys of its keyboard. It was set to Init Voice, with the following modifications:
Algorithm 1
Op1 Output Level 99
Op2 Output Level 99
Op3…Op6 Output Level 0
Keyboard Scaling all 0

We see that the waveforms of all keys except the highest key look similar, but not exactly the same. The highest key waveform looks very different. Maybe this is just a lowpass filter effect of the DX7 (certainly not of the scope, this is a 60 MHz scope). The frequency of the highest key is about 2 kHz.

If anyone wants me to measure something else, let me know!

Ingo









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