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Posted (edited)

How does the Chickenlips X16 sound chip or chips compare to the armsid chip? And which one is best? I mean I think the intent was many more voices for the sid but was cut short due to time constants. So sound wise I am not requesting any changes but just counting the voices and how sound is done between the sids and sound done differently on the x16. 

Edited by Travis Bryant moore
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Yes I think the idea was to have a bigger version of the SID. But the Vera's PSG and the SID differ in a few aspects:

Obviously count of voices. The SID has 3, the PSG has 16.

Volume control: the SID has analog ADSR envelopes. They sound nice and smooth, however, they aren't very flexible. The maximum volume cannot be changed. The PSG is more flexible: you can simply set a number as the voice's volume. This flexibility comes at the cost that the volume has to be updated manually. And the volume control is kinda coarse, so sometimes you can hear when the volume is updated to an adjacent level.

These were the two points where the PSG beats the SID. The other points all go to the SID. It has analog sound generation, while the PSG is fully digital. The difference becomes noticeable at high pitched sounds, where the PSG output can start to sound really unpleasant due to aliasing. The PSG also has no ring modulation, and, most importantly, NO FILTER. 

I think those are the most important points. But let's not forget that the X16 also comes with an FM chip, which nicely complements the PSG, and you cannot really compare it to the SID.

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Kliepatsch's Concerto demo shows you what kind of goodness can be made with the simple PSG functionality. What it loses in "features-per-voice" are made up by the sheer number of channels. If you bolt on a lot of your own modulations, such as PWM, or ADSR, then you can make the same kinds of sounds with the PSG as you could with the SID, with the exception of the filters and ring modulator. At its core, it's the same thing - 4 digital waveforms at selectable pitches. Also, the PSG can't key multiple waveforms on the same voice at the same time like SID can. But since there're 16 voices, the VERA PSG can actually generate MORE kinds of sounds than SID can in that regard, even if triggering all 4 waveforms simultaneously on one voice were possible.

 

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To pile on:  a few folks here have written assembly that uses the PSG, and programmatically manage ADSR-like envelopes.  It's only a matter of time before someone generalizes that code into an envelope controller thing or something.

For the kind of stuff I used to do on the C64, that's sufficient.

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2 hours ago, Travis Bryant moore said:

Can the FM chip do real sound or music or movie audio? Such as casset like audio or cd in an analog channel?

No, it's a frequency modulation synthesizer chip. So if there is an FM keyboard in the movie audio track, it can play the FM keyboard part. Not quite Beverly Hills Cop (that's a different FM chip), but the same idea. It's the chip in the Yamaha DX27, so if you search Youtube for DX27 patches, you can hear some of what it can do. Also, it was used in some arcade systems in the 80s.

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Was there a way to digitize auto and store it in a digital memory and convert back into analog sound? Say I ran a cd or 8 track into an analog to digital converter and stored it on a sd card and played it back though a digital to analog converter and maybe had the help with an amplifier? Or would such sounds be run by a Yamaha dx27? Old 8 track players had a pre amp and op amp and I think about 4 channels on the head reader not that matters other than it stored music on 4 channels on a single magnetic tape. And could the DX24 play one audio channel or more than one like a voice but dymanically shift the voice to emulate an audio channel?

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1 hour ago, Travis Bryant moore said:

Was there a way to digitize auto and store it in a digital memory and convert back into analog sound? Say I ran a cd or 8 track into an analog to digital converter and stored it on a sd card and played it back though a digital to analog converter and maybe had the help with an amplifier? Or would such sounds be run by a Yamaha dx27? Old 8 track players had a pre amp and op amp and I think about 4 channels on the head reader not that matters other than it stored music on 4 channels on a single magnetic tape. And could the DX24 play one audio channel or more than one like a voice but dymanically shift the voice to emulate an audio channel?

If I recall, there is a PCM playback channel in VERA. 

As to the DX7, that's an FM synthesizer, and it uses a similar chip as the Commander X16's YM2151. 

Most of this is covered in the FAQ, which is linked at the top of this page (although @Perifractic, the FAQ may need updating to cover the PSG.)

As to whether the CX16 compares to SID chips... I may be the only one who will say this, but I think the Yamaha FM synth blows away the SID in terms of sound quality, and if you add the PSG on top of that, there's simply no contest. The only Commodore sound system that can come close would be an Ultimate 64 with an FM cartridge installed. 

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9 hours ago, Travis Bryant moore said:

Was there a way to digitize auto and store it in a digital memory and convert back into analog sound? Say I ran a cd or 8 track into an analog to digital converter and stored it on a sd card and played it back though a digital to analog converter and maybe had the help with an amplifier? Or would such sounds be run by a Yamaha dx27? ... And could the DX24 play one audio channel or more than one like a voice but dymanically shift the voice to emulate an audio channel?

The thing about a keyboard synthesizer is that if you want to hit five keys at a time to play a chord, that means you need five channels. And if you want to have one key still fading while another key is being struck, they both need to have their own channel. So a "channel" is not like "front left, front right, back left, back right, bass" in a 4+1 surround sound but rather an electronically generated source of a particular tone.

So the DX 27 and DX 100 are the full sized and compact version of the same consumer level synthesizer. The DX21 is the higher end consumer version using the same chip but with more flexibility in how it uses it ... you could have different "instruments" in each half of the keyboard OR make an "instrument" from combining two different FM voices.

If the YM2151 does end up being in the finished CX16p, it will have even more flexibility ... if you want to be able to have five overlapping versions of one instrument, two overlapping versions of another one and an instrument that doesn't overlap, that can be programmed ... just as long as the total number of voices at one time is never more than eight. A lot of people who appreciate FM synths like the Bass 01 patch in the Yamaha presets, but other than that few people seem to like any of the other Yamaha presets and prefer patches that have been created by other people over the years.

Eight FM channels, 16 PSG channels and the PCM for waveforms that aren't effectively provided by the first two is a lot of flexibility in generating tunes in a chiptunes approach. But it's not focused on being a ".WAV" player, because that approach is bandwidth intensive for an 8bit system.

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1 hour ago, Travis Bryant moore said:

So the Vera is that a full wave player or having one of those if I put a cd rom drive in the cx16 could I then listen to some beach boys music?

If you'd like to see what the VERA's PCM playback system is capable of, I would recommend watching this video.

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4 hours ago, Travis Bryant moore said:

So the Vera is that a full wave player or having one of those if I put a cd rom drive in the cx16 could I then listen to some beach boys music?

That's the PCM, not the FM or the PSG. It would be using much more of the total processing power of the system to operate it that way than to generate sound in a chiptunes approach.

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Technically the VERA PCM is better than CD quality.

48KHz 16bit stereo.

However, like bitmap mode, turning all the options to max quality hits a wall where you really can’t feed it what it needs at those settings.

640x480 @8bpp won’t fit in VRAM. So you can have 640x480 OR 8bp, but not both.

48KHz 16bit stereo will fill 2MB quite quickly. (10 2/3sec roughly)

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34 minutes ago, ZeroByte said:

Technically the VERA PCM is better than CD quality.

48KHz 16bit stereo.

However, like bitmap mode, turning all the options to max quality hits a wall where you really can’t feed it what it needs at those settings.

640x480 @8bpp won’t fit in VRAM. So you can have 640x480 OR 8bp, but not both.

48KHz 16bit stereo will fill 2MB quite quickly. (10 2/3sec roughly)

CD quality is good enough. Mini Disc is good also. But I think it may be the audio compression that may also affect quality in some players.

 

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32 minutes ago, Travis Bryant moore said:

CD quality is good enough. Mini Disc is good also. But I think it may be the audio compression that may also affect quality in some players.

Except don't forget it's a 6502 hopefully running at 8MHz running the show, so there's not a lot of decompression algorithms that would be able to keep up with the higher quality output levels. If most players are written to support music play in games, those players will focus on generating music that doesn't suck up all the processing time on the music.

To fight against the design of the system in the way you are talking about and using the PCM like a modern audio player involves accepting a drop in audio quality.  So when you read the Vera programmers reference guide and see the possible settings of the PCM, like @ZeroByte says, don't automatically assume that each of the settings can be maxxed out at the same time and have something that the 6502 can keep up with.

48KHz/16bit mono might work for a complex waveform that the PSG can't handle and which would be hard to generate by FM synthesis. You find a length where the waveform repeats at 48KHz and repeat the wave, and that has to be a fraction of a second. That works best for percussion, because the length that the waveform cycles for different notes would be different. OTOH, if you are using the PCM to play a sample, you would step down to a lower frequency, lower resolution and likely mono.

From high frequency, high resolution, very short sample length, you could still have a pretty good gated Tom-Tom, since a Tom-Tom only needs to be versions of the sample for three tones, rather than a dozen for a bass or dozens for a piano ... and of course, the gated effect means you can avoid overlapping the Tom-Tom samples. A gated snare would also be possible, where the multiple versions of the wave are the different delays between snare strikes. A gated snare gets to the end of release fairly quickly, so a separate waveform for the attack, decay and hold portions, looping as appropriate, and playing with volume for the attach, decay and release as such, could make for a very nice gated snare.

An issue with both a single channel of FM and with PSG is that there are not a lot of complex harmonics in the tones, so it can sound "tinny", so if you fill in the harmonics with a more complex waveform played on the PCM and have a bass using two FM channels with related but not identical operators settings and tuned a couple of cents from each other, it can make for a much richer sound.

But if you want the villain to tell Mr. Bond that he has fallen into deep kimchi, then it's going to be mono, 8bits, and a much lower frequency.

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Posted (edited)

I think that is why the Amiga or expansion boards exist so you can hand off audio to one chip or expansion video to anther math co processor and so on with the main processors or center processor handles the addressing or routing to the other hand offs like an executive handing off jobs to other workers I suppose. Though I guess no one ever did the 8 bit machines like that.

Edited by Travis Bryant moore
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I’m considering a music player that will use 16-but output but 8-but input on PCM in order to gain lots of overhead for sample mixing. That will eliminate the need for pesky multiplication and division .

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I just have a question, for clarification's sake.

The FAQ has, under "audio":

Quote

There are 2 designs in final testing and one or both will remain:

  • Yamaha YM2151 sound chip
  • SID-like implementation in the VERA FPGA chip

Then, later, under the "VERA" heading:

Quote
  • 16-channel stereo Programmable Sound Generator with multiple waveforms (Pulse, Sawtooth, Triangle, Noise)

So.. the PSG is the "SID-like implementation", or are we getting that PSG and also one of the other options (TBD)?  Sorry, the FAQ isn't quite clear about it.

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7 minutes ago, John Chow Seymour said:

So.. the PSG is the "SID-like implementation", or are we getting that PSG and also one of the other options (TBD)?

The VERA PSG is the "SID-like implementation," as it can produce the same basic waveforms (pulse, sawtooth, triangle, and noise). However, it lacks some of the more advanced features, such as ADSR and filters.

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13 minutes ago, John Chow Seymour said:

In that case, I hope they find that it's possible to go with both the YM2151 and the VERA PSG.  As kliepatsch said earlier, they would complement each other well.

Quite. Without the filters, the bass line on the PSG seems like it would be a bit bland, while the YM2151 is famous for having a nice crunchy bass patch ... even out of the box, where the Bass patch #1 is really the only factory patch that people seem to like. Never mind the benefit of having hardware ADSR for "pew-pew" sounds.

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