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<font size="2"><span style="font-size:11pt" class="ContentPasted0">> A quick visit to Wikipedia says that PM does not alter the frequency</span></font></div>
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<font size="2"><span style="font-size:11pt" class="ContentPasted0">I think this shows the wisdom of consulting a proper text book. PM can alter the frequency but at the rate of change of the phase modulation rather than at the rate of the modulation itself.
Thus it's a first derivative effect.<br>
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<font size="2"><span style="font-size:11pt" class="ContentPasted0">If the modulation is a sine wave, then PM is actually a cos wave and produces the same output signal.<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Synth-diy <synth-diy-bounces@synth-diy.org> on behalf of brianw <brianw@audiobanshee.com><br>
<b>Sent:</b> 25 November 2022 23:42<br>
<b>To:</b> Donald Tillman <don@till.com><br>
<b>Cc:</b> synth-diy mailing list <synth-diy@synth-diy.org><br>
<b>Subject:</b> Re: [sdiy] Buchla 295 10-band comb filter topology</font>
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On Nov 25, 2022, at 2:59 PM, Donald Tillman <don@till.com> wrote:<br>
> On Nov 25, 2022, at 12:04 PM, brianw <brianw@audiobanshee.com> wrote:<br>
>> Yes, people label the B295 as a "comb filter," but I consider that artistic wishful thinking. Note that the frequencies on the panel are basically pseudo-log.<br>
> <br>
> No not the people; it was Don Buchla who literally labeled it a "Comb Filter". I'm pretty sure he meant it generically.<br>
<br>
Ah, thanks for the correction. I've never seen a B295, and the photos online seemed to only say "comb filter" on the clones. I clearly didn't look closely enough.<br>
<br>
I suppose "frequency response looks like a comb" is a fair description.<br>
<br>
<br>
> Just like "FM Synthesis" is really phase modulation, but the term is used generically.<br>
<br>
This has always baffled me. I understand the difference between frequency and phase, but my math skills aren't great enough to answer the question: Is there any way to phase modulate without frequency modulation? ... or the converse: Is there any way to frequency
modulate without phase modulation?<br>
<br>
A quick visit to Wikipedia says that PM does not alter the frequency, so I'm wondering how the DX-7 implemented that. I suppose the only way to tell would be to have a Chowning module where you could patch a DC CV into the PM input and verify that the frequency
remains the same, no matter what DC value the CV input takes. Unfortunately, I don't know of any voltage-controlled Chowning-style FM Synthesis modules. That would be an interesting analog/digital hybrid.<br>
<br>
My naive implementation of a single-operator FM on the Apple II (one modulator, one carrier) altered the frequency, so I guess I had no hope of ever building a Chowning voice (not considering the processing limits of a 1 MHz 6502). I suppose it's not too difficult
to imagine a different code implementation that would not alter the frequency (unless the modulator is a ramp wave, rising or falling).<br>
<br>
People also discuss the difference between linear FM and logarithmic FM.<br>
<br>
<br>
> And Leo Fender famously swapped "Tremolo" and "Vibrato".\<br>
<br>
That has bugged me for ages. I wonder if Leo can blame the psychoacoustic phenomenon where small changes in pitch are indistinguishable from small changes in amplitude. Then again, a whammy bar is hardly subtle.<br>
<br>
<br>
> This field has rich history of goofing up the terminology.<br>
<br>
Just like the fashion industry: naming fluorescent color dies as "neon." I mean, did they think they'd never have literal neon in clothing? Now that EL wire (electroluminescent wire) has been around for a decade or more, you can pretty much pull off "neon like"
clothing. Of course, neon/plasma is not electroluminescence, ... and there's also the catch that neon is used to excite the fluorescent coating in a fluorescent tube.<br>
<br>
Brian<br>
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