Sound Chip?

[ZeroByte]

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 .

[John Chow Seymour]

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.

[Elektron72]

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.

[John Chow Seymour]

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.

[BruceMcF]

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.

[Elektron72]

1 hour 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.

It's likely that the VERA PSG was designed to complement the YM2151, considering that the YM2151 was selected first.

[ZeroByte]

The YM2151 can really do some interesting things if you go "off-script" with it. For instance, the KeyON register has an interesting way of gating notes. Instead of a single gate for each voice, you can gate the 4 operators individually. This means that if you're clever with the ADSR values of the 4 operators, you could make a sound that features a continuous tone but with a cyclic modulation - so something that kind of goes WooWooWooWooWooWoo... - It's hard to describe this in text, but I'll give it a stab. (I'd have to make a program to demonstrate this as your typical tracker / OPM DAW plugin isn't going to offer this function either). Suppose your tone-generating operators have a D2R of zero - meaning that once the envelope reaches the sustain level, it will not decay anymore until you gate in a release on the voice. You start your sound by triggering all 4 operators.

e.g.: let's say operator 0 is the modulating operator

Now let's say one of your modulating operators does have a full ADSR with a D2R so the modulation runs its course.  Say the sound goes like oooOOOAAAAOOooo  (and stays "oooo" thereafter). You can re-trigger only that one operator and get another cycle of the effect w/o the sound ever decreasing its volume. So if you have some sound effect that represents something like a plasma beam firing, or a UFO engine, or something like that, you can just keep re-triggering the modulating operator to generate the effect.

Maybe I should try whipping something up in BASIC as a demo and do a "how-to" video on it or something.

[a9m]

On 6/14/2021 at 9:44 PM, ZeroByte said:

The YM2151 can really do some interesting things if you go "off-script" with it. For instance, the KeyON register has an interesting way of gating notes. Instead of a single gate for each voice, you can gate the 4 operators individually. This means that if you're clever with the ADSR values of the 4 operators, you could make a sound that features a continuous tone but with a cyclic modulation - so something that kind of goes WooWooWooWooWooWoo... - It's hard to describe this in text, but I'll give it a stab. (I'd have to make a program to demonstrate this as your typical tracker / OPM DAW plugin isn't going to offer this function either). Suppose your tone-generating operators have a D2R of zero - meaning that once the envelope reaches the sustain level, it will not decay anymore until you gate in a release on the voice. You start your sound by triggering all 4 operators.



e.g.: let's say operator 0 is the modulating operator



Now let's say one of your modulating operators does have a full ADSR with a D2R so the modulation runs its course.  Say the sound goes like oooOOOAAAAOOooo  (and stays "oooo" thereafter). You can re-trigger only that one operator and get another cycle of the effect w/o the sound ever decreasing its volume. So if you have some sound effect that represents something like a plasma beam firing, or a UFO engine, or something like that, you can just keep re-triggering the modulating operator to generate the effect.



Maybe I should try whipping something up in BASIC as a demo and do a "how-to" video on it or something.

Let me explain this. Basically you can start and re-start envelopes independently on each operator. Depending on how you set up connections you can either do echos or crude LFO without restarting the main carrier's envelope.

[ZeroByte]

2 hours ago, a9m said:

Let me explain this. Basically you can start and re-start envelopes independently on each operator. Depending on how you set up connections you can either do echos or crude LFO without restarting the main carrier's envelope.

Heh- yeah, what he said. ?

 

[thetraintomars]

On 6/15/2021 at 1:16 PM, a9m said:

Let me explain this. Basically you can start and re-start envelopes independently on each operator. Depending on how you set up connections you can either do echos or crude LFO without restarting the main carrier's envelope.

I've been using a Yamaha DX Reface and each operator has it's own independent envelopes, I take it the YM2151 is designed to work in a similar fashion?  I'm trying to find tech docs so I can understand what the chip can do and what features will need to be programmed.