Search found 2396 matches

by TmEE co.(TM)
Sun Jun 21, 2020 9:02 pm
Forum: Sound
Topic: YM2612 & distorted sound output
Replies: 7
Views: 555

Re: YM2612 & distorted sound output

The output is a pulsetrain, with YMCLK / 144 clocks per sample and 24 clocks per pulse (with differing duty cycle and amplitude for 3438 and 2612). There's harmonic content going into MHz range in there so you need fairly good opamps to deal with it effectively. The output is also very weak and shou...
by TmEE co.(TM)
Sun Jun 14, 2020 4:17 pm
Forum: Sound
Topic: YM2612 & distorted sound output
Replies: 7
Views: 555

Re: YM2612 & distorted sound output

YM2612 and YM3438 have pulse train based outputs where all channels are sent sequentially. On 2612 the pulses are very narrow and also have fairly low amplitude while 3438 has much wider and bigger pulses, allowing for better SNR. What you see on your scope is mainly due to aliasing, when you up the...
by TmEE co.(TM)
Sun May 17, 2020 11:30 am
Forum: Megadrive/Genesis
Topic: VDP 8x16 Interlace Mode
Replies: 7
Views: 853

Re: VDP 8x16 Interlace Mode

Possibly but these are buried into past that is many years ago...
by TmEE co.(TM)
Fri May 15, 2020 10:41 am
Forum: Megadrive/Genesis
Topic: VDP 8x16 Interlace Mode
Replies: 7
Views: 853

Re: VDP 8x16 Interlace Mode

It is good for still images, you see markedly higher detail. When things begin to move there will be various interlacing related artifacts appearing.
Here's couple experiments I made a while ago :
http://www.tmeeco.eu/SMD/HIRES.BIN
http://www.tmeeco.eu/SMD/INTERLAC.BIN
by TmEE co.(TM)
Thu Apr 30, 2020 9:39 am
Forum: Sound
Topic: SN76489 polarity
Replies: 4
Views: 961

Re: SN76489 polarity

There's no negative polarity on TI/VDP PSG and most other PSG type sound chips. You do get stuff settle below ground level when you highpass filter the final chip output as it is done on all hardware outside the sound chip itself. On the TI/VDP PSG, outputs start high and toggle between 0 and a high...
by TmEE co.(TM)
Sun Mar 08, 2020 11:09 pm
Forum: Mega/SegaCD
Topic: Best solution for anime VisualNovel
Replies: 3
Views: 2049

Re: Best solution for anime VisualNovel

When you play CDDA you lose access to the CD drive more or less so whatever you want to show will have to fit in the RAM, and you have limited amount of that.
by TmEE co.(TM)
Thu Jan 30, 2020 11:23 am
Forum: Cartridge
Topic: Designing MD sdcard flashcart for fun, advice?
Replies: 37
Views: 13481

Re: Designing MD sdcard flashcart for fun, advice?

I guess it'll work then, I hope there won't be more troubles with the new version ~
by TmEE co.(TM)
Thu Jan 30, 2020 2:45 am
Forum: Cartridge
Topic: Designing MD sdcard flashcart for fun, advice?
Replies: 37
Views: 13481

Re: Designing MD sdcard flashcart for fun, advice?

I think it would work, assuming flash is fine with its !CE always low. Logic itself should be sound, disregarding any timing issues.
by TmEE co.(TM)
Thu Jan 16, 2020 12:34 pm
Forum: Hardware
Topic: Cartridge slot questions
Replies: 23
Views: 7653

Re: Cartridge slot questions

MD2 VA0 and VA1 do not have 75ohm load on the cartslot signals. 32X just has very low output impedance amp that can drive headphones (i.e 16 ohm load), there's no variation in output level due to it. You just need a beefy amp to make things work.
by TmEE co.(TM)
Thu Jan 16, 2020 10:29 am
Forum: Hardware
Topic: Cartridge slot questions
Replies: 23
Views: 7653

Re: Cartridge slot questions

Sik wrote:
Thu Jan 16, 2020 12:44 am
Anyway, if I'm understanding correctly this means the audio output (as far as the cartridge slot goes) is ±2V, excluding bias?
Yup, +/-2V into 75ohm load is the target for cartslot audio.
by TmEE co.(TM)
Thu Jan 16, 2020 12:25 am
Forum: Hardware
Topic: Cartridge slot questions
Replies: 23
Views: 7653

Re: Cartridge slot questions

The clipping is due to the mixing+amp chip, it isn't rail-to-rail IO capable (but it can get very close to ground due to special design, with top side being typical ~1V shy from a power rail) and due to it there will be early clipping. If the attenuated and filtered PWM signal was given a DC offset ...
by TmEE co.(TM)
Wed Jan 15, 2020 5:43 pm
Forum: Hardware
Topic: Cartridge slot questions
Replies: 23
Views: 7653

Re: Cartridge slot questions

I have not seen the edit, I was waiting for a new post lol. I'll do measurements soon. 32X audio output is almost 4Vpp on the cartslot pins, and it clips early, both tips of the sine are flat. There's a 45Hz -3db point high pass filter forming in most MDs (47µF cap in 32X, 75ohm load on most MDs). A...
by TmEE co.(TM)
Fri Jan 10, 2020 4:19 am
Forum: Cartridge
Topic: Designing MD sdcard flashcart for fun, advice?
Replies: 37
Views: 13481

Re: Designing MD sdcard flashcart for fun, advice?

That is a pretty nice writeup ~
by TmEE co.(TM)
Thu Jan 09, 2020 9:37 am
Forum: Hardware
Topic: Cartridge slot questions
Replies: 23
Views: 7653

Re: Cartridge slot questions

Someone make me a 32X test ROM with same sort of grayscale ramp as seen here : viewtopic.php?f=22&t=2188

And while at it, play a full scale sinewave on both L and R side, I'll get the scope out and measure the levels at various points.