<html><body>Hi, <div>my first comment here...<div>I have had big stress with my DX7 mk.I. digital sig noise,</div><div>since I realised it on Headphones </div><div>after some months from a spawnshop buy.</div><div>I Googled a lot, found schematics,</div><div>also looked over forums around,</div><div>and if anybody ask for antialiasing,?</div><div>Isnt this question about more or less filtering</div><div>of output from DAC ? </div><div>Cause of ol original DX7 noise for example</div><div>is that thing of switching MOS 4 bit <span style="line-height:1.5;background-color:transparent">R2R</span><span style="line-height:1.5;background-color:transparent"> </span><span style="line-height:1.5;background-color:transparent">add-on </span></div><div><span style="line-height:1.5;background-color:transparent">for 12 bit ADC, and S-H for 4(6 ?) chanell of voise,</span></div><div><span style="line-height:1.5;background-color:transparent"><br></span></div><div><span style="line-height:1.5;background-color:transparent">Thinking bout upgrading it for a cleaner sound of DX7 Mk II/ D FD</span></div><div><span style="line-height:1.5;background-color:transparent">found that these have S-H swithed to stereo out from one single PCM57 ADC.</span></div><div><span style="line-height:1.5;background-color:transparent"><br></span></div><div><span style="line-height:1.5;background-color:transparent">but signals and OPGenerator out wiring are quite different ?(</span></div><div><span style="line-height:1.5;background-color:transparent"><br></span></div><div><br></div><div><br></div><div>Antialiasing algorithms in FM ?</div><div>Gues it as so DSP hungry and difficult,</div><div>that original FM synth buiders didnt even think bout that.<br><br>-- <br> s pozdravem
<br>Petr M
<br>(+420)608228257 ...<<<<<<< *<:]<> Pom.ixsss...<br><br><aside>
---------- Původní e-mail ----------<br>
Od: KD KD <pic24hj@gmail.com><br>
Komu: synth-diy@synth-diy.org<br>
Datum: 8. 9. 2018 0:56:55<br>
Předmět: Re: [sdiy] TX81Z, YMxx chips, and aliasing
</aside><br><blockquote data-email="pic24hj@gmail.com">Yes, i think all yamaha PM synths have keyboard scaling to change<br>modulation index.<br>e.g page 144 SY99 manual 4 breakpoints describes how the level of a<br>modulator or operator over keyboard are freely scaled. All waveforms<br>are mathematical transforms<br>of sines.<br><br>2018-09-05 14:14 GMT+02:00, rburnett@richieburnett.co.uk<br><rburnett@richieburnett.co.uk>:<br>> As Michael said, the FM spectrum is theoretically infinite even with a<br>> sinusoidal carrier and modulator.<br>><br>> However, I believe that synths like the DX-7 reduced audible aliasing by<br>> employing mappings across the keyboard that decreased the modulation<br>> index of patches progressively for higher pitched notes. Reducing the<br>> modulation index in Frequency Modulation puts less energy into the<br>> higher-order sidebands and more energy into the close-in sidebands from<br>> the FM process, so it results in a signal that has less potential to<br>> alias badly.<br>><br>> -Richie,<br>><br>> On 2018-09-05 12:56, Declare Update wrote:<br>>> Ah! very good point. thanks.<br>>><br>>> Chris<br>>><br>>>> On Sep 5, 2018, at 4:14 PM, Michael Zacherl <sdiy-mz01@blauwurf.info><br>>>> wrote:<br>>>>> On 3 Sep 2018, at 09:43, Declare Update <declareupdate@gmail.com><br>>>>> wrote:<br>>>>> Do the yamaha FM chips, such as the YM2414 in the TX81Z, do anything<br>>>>> toward anti-aliasing? more specifically, does anyone know if they use<br>>>>> band limited tables for their extra wave forms besides sine, and is<br>>>>> there any attempt to band limit the signal after FM is applied?<br>>>><br>>>> On the bottomline bandlimiting the source wave forms is moot, since<br>>>> it’s the FM’s sidebands which cause the aliasing (and are responsible<br>>>> for the rich spectrum).<br>>>> So even when using just sine waves you may get side bands which get<br>>>> above Nyquist and/or below zero.<br>>>> m.<br><br>><br><br>_______________________________________________<br>Synth-diy mailing list<br>Synth-diy@synth-diy.org<br>http://synth-diy.org/mailman/listinfo/synth-diy<br></blockquote></div></div></body></html>