I've recently made my NES output stereo by adding 2 extra RCA jacks (red and white) connected to CPU Pin 1 and 2. Most tutorials say to use 1uF capacitor, however, I used 220uF and must say that the output is alot better that way in my opinion yet still has alot of noise (so does Mono btw).
Is there a way to reduce the noise or is it fault of the CPU itself?
Also, I was wondering if it is possible to replace the XTAL in a PAL NES (26.601712MHz) with a
28.6363MHz to get 1,79MHZ Clock speed, which is as close as the NTSC XTAL. Perhaps one could add a switch between them?
Or will the mod only work properly when adding NTSC CPU/PPU/XTAL?
If I would do the last option, isn't it possible to switch between true PAL and true NTSC?
If you inverted one of the two signals and mixed them back together with the right balance you might be able to get a cancellation on the noise. Of course, then you're back to mono.
For your first question, the NES is officially mono and all games were written in this scope. All those so-called "stereo" mods simply does not make sense.
As for your second question, yes it is possible, however you won't get a NTSC-compatible NES just by changing the crystal alone, as the PPU will also be overclocked. It will generate a PAL signal with invalid timing (too fast) that the TV won't recognize, so while the sound will be perfect (the dumbed down pitch will be correct again), you won't see anything.
The closest you could try to get a NTSC-compatible PAL NES is overclock the CPU so that it is aprox. 1.79 MHz and overclock the PPU so that it outputs an approx. 60Hz frame rate, so TVs that recognizes a 60Hz PAL signal would display a correct image, and the game would play faster. If you don't care about sound pitch being too low you don't even need to overclock the CPU.
In this case all games with timed raster effect, such as Rad Racer, won't work, because the CPU/PPU alignment is neither going to be the stanrard 3x (NTSC) nor 3.2x (PAL).
In the end, I guess the best bet would be to overclock the PPU to output a 60Hz frame rate, and overclock the CPU so that the dot/cycle ratio is 3x, just as in an NTSC console (I'm too lazy to do the math and figure out which frequency that'd be). The sound's pitch will then be off tune again, but at least you have compatibility with some raster effects of NTSC games. However, anything that is timed from an NMI interrupt will still be off, because the VBlank will still be 70 lines (PAL) instead of 20 (NTSC). The NTSC-compatible PAL famiclone solved this issue by triggering the NMI late, after the 50th VBlank line. However there is no way to mod the PPU that way, because this is hard-wired in it.
In other word no matter what you do to your PAL console it will never become 100% compatible with it's NTSC counterpart, you can only make a part of it compatible and break another part. Of course you could change the chips for NTSC chips, but then you have to improt a NTSC console anyway so why bother with the soldering ?
Ice Man wrote:
Also, I was wondering if it is possible to replace the XTAL in a PAL NES (26.601712MHz) with a
28.6363MHz to get 1,79MHZ Clock speed
You will lose color on the PPU if you go that route. I'd recommend getting one of those Dendy clone CPUs, which divide the PAL master clock by 15 instead of 16, if you can find one.
I thought about adding a circuit to delay the negative edge of /NMI by 50 lines to improve compatibility, but then I realized that that won't work because OAM DMA doesn't work on the 2C07 (PAL NES PPU) outside lines 241-260 even during forced blanking because its DRAM refresh was reworked.
I see. Thanks for the info guys.
However, did someone make a switchable NTSC/PAL NES already?
My original idea was this:
Get NTSC PPU,CPU, XTAL from an unused Famicom/NES.
Piggyback the NTSC parts to their PAL parts within the console but leave the 5V pin floating.
That way I can switch which parts get 5V (enabled) or not (disabled).
Or would I need to do this with the RST pin also?
@Breg: I know the NES is originally mono but that way you can mix audio channels, which is quite nice.
P.S. Is this the mod (inversion) you're talking about?
No, I have no idea what "mod" that is. It looks like a mono mix, filters, and an amplifier? Is that a mod or just a schematic of the NES?
Inverting one of the two channels is just a thing I'm suggesting, I've never heard of someone doing it on an NES. It's a principle used in guitar pickups, though, two pickups of opposite polarity will cancel each others' noise while boosting their common signal ("humbucker"). The main problem with doing this to the NES, is that the two pins aren't supposed to have equal output levels, which you will have to do to cancel the noise.
Nevermind, it's the default audio path for the NES. I must've mistaken something there. :S
Quote:
Piggyback the NTSC parts to their PAL parts within the console but leave the 5V pin floating.
That way I can switch which parts get 5V (enabled) or not (disabled).
This should be possible of course but why going through this trouble, since you have 2 consoles already just use the one you need to play a NTSC/PAL game.
You're just taking the risk of destroying everything.
While that may be true I want an all in one NES. I've already modded it to play Famicom games with an in built adapter. Simply plug in the game on top of the console
like this.
The downside right now is the internal speed, since famicom games are NTSC also.
I can however, mod my NTSC NES that way as well, but that's more costs imo.
Ice Man wrote:
Also, I was wondering if it is possible to replace the XTAL in a PAL NES (26.601712MHz) with a 28.6363MHz to get 1,79MHZ Clock speed, which is as close as the NTSC XTAL. Perhaps one could add a switch between them?
Tepples already covered this, but there are a
wide variety of
differences between the PAL and NTSC NES, and adjusting the CPU speed only fixes one of them.
I'm a little biased, but honnestly once you have imported a NTSC console there is very little reason to touch your PAL console ever again. Unless you plan to play Asterix, the Smurfs or Elite, everything else plays better on NTSC as it was designed to.
PAL versions are quick fixes that does not fix gameplay speed, and they only fix raster effect. Later in the NES lifetime they started to fix music tempo and pitch, but they never fixed gameplay speed, exept in the revision of Super Mario Bros, and I don't like this version because they overfixed it and it is too fast.
That or the "High Hopes" demo.
Did I fix
Thwaite properly for PAL?
Ice Man wrote:
Piggyback the NTSC parts to their PAL parts within the console but leave the 5V pin floating.
That way I can switch which parts get 5V (enabled) or not (disabled).
Or would I need to do this with the RST pin also?
Don't do that with the 5V pin. The parts would still be seeing 5V on the data bus and any other inputs, which will power and/or destroy it. To do it right, you would need to power it, hold it in reset, and isolate all the ouputs that aren't tri-state (which I believe would include the entire address bus). You're really better off just getting a second console, or socketing the parts and swapping them out entirely.
edit: not sure what to recommend for the crystal. But to make the IC swapping easier, put a socket on the board and leave the IC permanently in the same type of socket. That makes swapping easy (the cheap type of sockets, not the machined pin type).
Bregalad wrote:
PAL versions are quick fixes that does not fix gameplay speed, and they only fix raster effect.
Some times not even the raster effects, as evidenced by Mega Man 3.
Memblers wrote:
Ice Man wrote:
Piggyback the NTSC parts to their PAL parts within the console but leave the 5V pin floating.
That way I can switch which parts get 5V (enabled) or not (disabled).
Or would I need to do this with the RST pin also?
Don't do that with the 5V pin. The parts would still be seeing 5V on the data bus and any other inputs, which will power and/or destroy it. To do it right, you would need to power it, hold it in reset, and isolate all the ouputs that aren't tri-state (which I believe would include the entire address bus). You're really better off just getting a second console, or socketing the parts and swapping them out entirely.
edit: not sure what to recommend for the crystal. But to make the IC swapping easier, put a socket on the board and leave the IC permanently in the same type of socket. That makes swapping easy (the cheap type of sockets, not the machined pin type).
Oh I see.
Thought it would be at least a little bit easier. Ah well..
Thanks for all the help here, really appreciate that.
Don't feel bad. I just imported a PAL Commodore-128 from Germany to Japan, because there's very little that's compatible/worthwhile in the NTSC-DTV world.
Sometimes we gotta take these extreme measures and never look back.