Search found 92 matches

by foobat
Sun Jun 22, 2014 10:34 am
Forum: Hardware
Topic: Check my ac adaptor
Replies: 5
Views: 6105

The only way to check to see if they can provide the rated current is to connect them to the rated load. The tool to do this is called a "dummy load" or sometimes (paradoxically) a "load generator". It's effectively a series of resistors, and that's basically the same thing as an electric heater. Yo...
by foobat
Fri May 16, 2014 6:28 am
Forum: Megadrive/Genesis
Topic: Sega Mega Drive/Genesis Collected Works
Replies: 18
Views: 16789

Thanks for the heads' up! I totally preordered
by foobat
Thu May 01, 2014 4:22 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

It needed some kind of case to survive the trip overseas, and there was a can of spraypaint nearby...

Image

can't let good spraypaint go to waste
by foobat
Sat Apr 26, 2014 6:26 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

The chip doesn't mind a voltage divider if you use it *after* the coupling cap that removes the DC component, so you can use that technique to reduce the signal to something the amp can handle. I have to do this for the lm386es, you can see it at the 12k<->220k divider after each of C30 through C33....
by foobat
Sat Apr 26, 2014 3:01 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

Haha, well, I took a scope to it today and found out that it was clipping the bottom half of the audio not the top half - the elimination of the 12k pulldown resistor that the YM2612 needs and the elimination of the 10uf cap are the only changes necessary to support the ym3438. I did find out someth...
by foobat
Wed Apr 23, 2014 8:16 pm
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

Sweet! Thanks, guys. I'll come up with something. @Aly, I'll send you a device with one YM2612 and one YM3438 when I get it ready, and I'll update the board layout to have selectable voltage dividers. Automatically detecting the YM3438 will probably be too much for me, so we're gonna have to use a s...
by foobat
Wed Apr 23, 2014 10:01 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

That shouldn't be a thing because I'm using an oscillator IC instead of just a crystal.

That schematic is... interesting. There's no load on MOL! I thought this thing would burst into flames with no pulldown on MOL and MOR?
by foobat
Wed Apr 23, 2014 3:28 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

Today I got my YM3438 chips in, which will require a hardware change to support. It's definitely much louder than the YM2612 and might require a voltage divider at the coupling capacitor. It's definitely clipping. I should be able to figure out how to fix it with a scope and I remember reading somew...
by foobat
Fri Apr 18, 2014 5:02 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

First prototype assembled and fully functional!

YouTube: https://www.youtube.com/watch?v=sqC9TVTOV_M
Image
by foobat
Tue Apr 15, 2014 10:23 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

@gigasoft: 12-tone polyphony is a goal of this project. It's probably the default mode that you'll use when playing over MIDI, although the option to switch to one MIDI channel per channel will be selectable. This is fairly easy to do and in fact there is already code that does it. The workflow I've...
by foobat
Tue Apr 15, 2014 5:28 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

Cool! No rush. I'm deep into doing a Monome-like sequencer too so my plate is full enough for the next couple weeks ;)
by foobat
Tue Apr 15, 2014 3:13 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

Aah, ok. That's interesting. I'll figure that out later and get it to work. I got the first run of boards in today and started assembling them! I'm still waiting for some parts to come in from Digikey so I can't do anything big yet. But I did power up the Teensy and make sure there are no shorts on ...
by foobat
Thu Apr 10, 2014 5:34 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

Not sure why one of the drum samples didn't make it. Hmm. Might have overflowed the sram
by foobat
Thu Apr 10, 2014 5:24 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

sure! I kind of halfassed the recording with a usb capture thing, but it shouldn't matter much since the thing is still just on a breadboard anyway. Took a picture too ;) saved it as a huge flac file so it sounds as close as possible to the original output http://7355608.net/alyrecording.jpg http://...
by foobat
Tue Apr 08, 2014 4:58 am
Forum: Sound
Topic: Dual-YM2612 hardware synthesizer
Replies: 53
Views: 69864

The deal is that to playback audio via the DAC, a VGM file records the transactions on the bus between the Z80 and the ym2612. A VGM also contains a recording of the time that the z80 spins in a tight loop waiting for the next instruction. In order to play back the vgm file, you need to act on each ...