What I discovered about PCM waves

[AlenK]

Like the Synth waves not much is described about PCM waves beyond a list of them in the Appendix. But as I discovered when I auditioned them in an XW-P1 they exhibit complexities worth knowing when you're trying to create your own sounds. Although the wave numbers and particulars will be different in a G1 the general concept is the same, which is why I'm posting this in the XW General Discussion area. PS. If I am mistaken about anything I write below I'm sure Mike will correct me.

First, most, but not all, of the PCM waves in the P1 from 0000 to 0774 are multi-sampled (0000 to 0310 in the G1). That is, different samples are used in different pitch ranges. If you want to know what samples and how many look at waves 0789 to 1608 (0607 to 1227 in the G1). These are all the components - in most cases looped samples - that make up the multi-sampled waves. Note, for instance, that there are 150 piano waves in the P1, organized in six groups of 25. Is it a coincidence that the stereo PCM piano tones in the P1 exhibit three intensity levels (triple strike) and that 3 x 2 (stereo) = 6? I don't think so. The G1, which has a double-strike piano and a few less piano presets, has only 44 piano waves.

Drum waves in the P1 appear from 1609 to 1849. These are followed by synth waves from 1850 to 2157. None of the waves from 1609 to 2157 are multi-sampled, indicated in the appendix by the footnote "With these waves, one type of wave is allocated to the entire tone range. They cannot be selected by a hex layer tone." The synth waves are the same ones in the synth wave list, indicated by the footnote "These waves are the same as the synth waves." (!) However, the two lists are not _exactly_ the same, since the synth wave list includes three "PWM" waves missing from this one.

In the G1 the drum waves run from 1228 to 1608, followed by 50 "groove" percussion samples from 1609 to 1658. Ten percussion noise samples follow from 1659 to 1668 and the same 14 noise types offered by the solo synth's noise oscillator from 1669 to 1682. Finally, the synth waves follow from 1683 to 1990.

In the P1 the waves from 0775 to 0788 are the noise waveforms, the same 14 available from the solo synth's noise oscillator.

Curiously, you may have noticed waves from 0652 to 0774 in the P1 with the prefix "Sy_" (0470 to 0592 in the G1). And you may also have noticed that these waves appear to be named similar to the synth waves in the list from 1850 to 2157 (1683 to 1990 in the G1). It turns out that they are almost, but not quite, the same. The difference is that most of the Sy_ waves are multi-sampled. You can see that there are more synth waves (180+ more) in the list from 1850 to 2157 (1683 to 1990 in the G1). They include a lot of -L and -B waves that are harmonically richer than the "normal" versions and are intended to be played at lower octaves. These -L and -B waves are already combined with the normal waves in the multi-sampled versions.

What you can do with these waves depends on what sound engine you use. The preset PCM melody and drum tones call up the waves they need from the list automatically. The melody tones already incorporate multi-sampling (when applicable) and velocity switching. The drum tones don't do either. They aren't (and don't need to be) multi-sampled and velocity switching gets implemented in the drum sets that call them up.

There is no way to tell which waves a given PCM melody tone (or drum tone for that matter) uses or exactly how it uses them but you can guess a fair bit from the list. Mind you, you can't change which waves a tone uses. All you can do is edit things like cut-off, attack, release, etc and add or change DSP effects. In the case of drum sets you do get to see which drum tones are used for each key and each velocity range per key and you can change them to make your own drum set.

In the hex-layer engine (P1 only, of course) you can call up any of the waves from 0000 to 0788, most of which are multi-sampled. Note that all of these were sampled at one particular velocity (intensity) level. If you want velocity switching you have to set that up yourself.

In the solo-synth engine you can select the PCM waves from either of the PCM oscillators. There are no restrictions; you can call up multi-sampled waves, non-multi-sampled waves, synth waves, noise waves, drum waves, whatever. Compared to the solo synth's two "synth" oscillators all you give up is the ability to do PWM and hard sync. Given that both of those modulations aren't implemented in a band-limited way and that PWM has additional artifacts that render it almost unusable (IMO) that's hardly a great loss.

It's interesting to note that the waves sound different in the different engines. In the case of the solo synth a PCM oscillator doesn't "listen" to a wave's pre-programmed amplitude envelope, when such exists. You get the "raw" sample, with an infinitely looped sustain if the sample is looped. The hex layer engine, on the other hand, does observe a wave's envelope (or is supposed to) and the adjustments you make to the envelope parameters are offsets from that (with apparently a few bugs).

However, the hex layer engine doesn't observe any DSP effects or filtering that may be associated with a wave when it is used in a preset PCM melody tone. It may seem obvious that this would be the case except that some of the waves are actually named as if they have a DSP effect added. Consequently, many waves sound practically identical to others when used in the solo-synth and/or hex-layer engines; you don't really get quite as much variety as the size of the PCM wave list would suggest. But there is still plenty of variety there. The sound creation potential of the XW synths is truly vast (but not V.A.S.T. if you know what I mean ).

UPDATE: I have edited the post above to include wave numbers for the G1 as well, just in case this ends up in a FAQ.

[Null]

Brilliant analysis as always Alen. Perhaps we should be looking to you to write the much needed companion volume to the XW Manuals which all of us have been crying for. Our pleas to Casio so far have fallen on deaf ears.

Gary

[AlenK]

Thanks. GREAT idea but I would have to dive into the XW-P1 more than I have so far. I've only had the thing a little over a month, after all. Ideally, someone should have started such a book 12 months ago or even earlier (the latter would have been possible using a pre-release unit provided by Casio). In any case I'll continue to post whatever I discover here as a community service. If everyone does the same we should build up a good body of knowledge. That's one of the primary purposes of the forum, as I see it.

[Null]

At the very least, you should collate all of your posts as well as any tidbits you might stumble upon along the way and put them into a FAQ type file for easy and quick reference by all.

In fact, perhaps Mike and the board's sysadmins could create a special FAQ section right here on the forum so that people wouldn't have to search a couple of thousand postings in order to find that single crucial bit that eludes them 3 months after they vaguely recall reading about it here.

How about it Mike? Doable? To be honest I've never seen a support forum WITHOUT a FAQ section.

Gary