Hi everyone, I forget if I already mentioned elsewhere, but I'm new to synth design and for my first project I want to emulate the NES sound device (2A03), which I've got over halfway complete.

There's alot of detailed specs for the 2A03, even a manual on programming the hardware, and that helps alot but it still takes me a long time to figure out how to emulate some of the effects. The how~ forum has been very helpful, but I was wondering if anyone else here is into the "8-bit sound", and does any designing/composing with pd?

Once I finish my 2A03 project and get some experience, I want to move on to emulating the Sega X-Board sound devices, or the Seta x1-010 both of whch seem to have no technical documatation available. Anyone know a good way for analyzing obscure sound devices? Alot of times it's difficult to get samples where only 1-2 channels are playing.

Hi, nice idea!

@c0dav0x said:

There's alot of detailed specs for the 2A03, even a manual on programming the hardware, and that helps alot but it still takes me a long time to figure out how to emulate some of the effects. The how~ forum has been very helpful, but I was wondering if anyone else here is into the "8-bit sound", and does any designing/composing with pd?

There was a nice patch by zenpho posted some time ago in the forum (or the mailing list) some time ago

http://www.zenpho.co.uk/chipwave.shtml

that emulates the chip sound quite well. Have a look at it..

Just for curiosity, to which extent do you emulate the 2A03 in pd?
I mean, basic HW spec? How you do it?

About artist doing 8bit sounds, do you know

http://www.headlessbarbie.com/ ?

I heard his songs, very interesting!

cheers

Alberto

Well for now I'm concerned about getting an authentic sound without worrying too much about emulating the specific operation of the hardware. I also want to add a few extras that the original didn't have, like vibrato, sweeping of the triangle channel, and maybe some other small odds and ends.

The pulse channel sound is simple to emulate, especially if you aren't concerned about timing their length & envelope data against other components, like the frame counter or interrupt lines. The triangle is a bit trickier to get authentic.

The noise channel is particularly difficult to emulate, at least for the inexperienced like me. The NES noise sound in itself is easy to reproduce as a sample using 4bit level quantized noise. The 2A03 actually uses a long shift register and a XOR gate to generate a new pseudo-random bitstream for noise samples. Rather than use my very own enveloping like I did for pulse and triangle channels, I will have to reproduce the native specs of the counters/timers and decay envelope modes, especially to get the looped-decay noise channel mode to sound authentic.

So I guess I will be using some of the same dataflow and control logic that the hardware uses, but I want to cut as many corners as I can right now, especially where I can easily provide userdata through the GUI instead of poking 6502 assembly. Then I can use my own, simpler methods for programmable manipulation of all of the inputs, but ideally get the same-sounding output as I would programming the actual hardware.

Right now I'm going through this document to try and get a full picture of the hardware:
http://nesdev.parodius.com/NESSOUND.txt

I believe that has everything needed to directly emulate the channels, I just gotta keep studying the hell out of it until I can determine all of the specifics on timing, mode switching, sample sizes and such.

The zenpho patch looks similar to what I want to use eventually for making real music, I'll probably refer to that a few times. I see he uses a completely diferent PWM routine than I do. Once I get the NES channels sounding properly, I plan to keep adding voices from other old sound chips I enjoy along with more extras and use it as my main synth.

Thanks alot for that headlessbarbie link. Really amazing stuff. I've had thoughts about later on trying to emulate the 2A03 hardware directly, so that I possibly could put pd on a board with a fast CPU (maybe a SuperH) that would be small enough to fit in a NES cart. Then I could use pd as just an interpreter between the user and the real live sound hardware.

well, I've got the four main instruments and the panelling done for my pd-NES, all that's left is to add glue for the sequencing and composition tools. I had to cheat pretty badly on the noise channel though. For the standard noise mode I used the method from zenpho which looks simple and sounds good, but I noticed he didn't emulate the looped-decay noise mode, which all my resources describe as being "difficult", but otherwise provide slightly different explanations of the mode. It appears that emulators and other software that fully emulate the noise channel seem to "wing it" and use their own unique methods. I'm guessing it's because the actual hardware driving the random number generator kicks out one random bit to the 4-bit DAC at 890KHz, which I guess I can't simulate in pd unless I could change my sampling rate to 445kHz (for 4bit codes). I haven't found a good explanation of what happens to each bit - apparently the hardware updates one of two different bit sequences (a 93-bit sequence and a 32kbit sequence, the latter of which makes no sense to me - that's a big load on the memory bus). I've tried creating different kinds of noise generators or 93bit noise samples, and looping them with an interpolating sampler and decay envelope, but it never sounded right. The problem is the noise itself - no matter how fast I loop I never get a smooth tone, or I still hear regular noise over the tone.

I ended up ripping the looped noise sounds from NES games and an emulator, storing them as timbre presets, and using soundfiler and elementary granular methods to transpose. It's definitely cheating, but it doesn't limit me to the 16 pitch colors that the hardware has to choose from. So I got what I wanted, the NES sound without all the NES limitations, but I'm a little frustrated that I couldn't find a solution that uses only generators as opposed to external samples.

Does anyone have a recommendation for correctly emulating the looped-decay-noise sound? I've attached a wav ripped from Megaman that has a D# tone at four different timbres (caused by different decay strengths in the envleope).

http://www.pdpatchrepo.info/hurleur/nnlx4_ds.wav