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Cleaning up NES audio output
https://forums.nesdev.com/viewtopic.php?f=9&t=7380
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Author:  m00dawg [ Thu Jan 13, 2011 8:39 am ]
Post subject:  Cleaning up NES audio output

The audio output of my NES is super buzzy taking it from the standard audio out. It's fine for listening but very poor for recording. I am playing custom made NSFs (using FamiTracker) via my PowerPak and the problem is that the buzzing is at a pitch, producing some discords.

Add to that the fact that I may need to record specific channels (meaning I have to record off it multiple times for the same song) and you have a compounding of the problem.

Shiru on #nesdev suggested using a battery instead of the wallwart. This seems to have helped marginally but I think most of the noise is coming from the cartridge and somewhere within the NES audio path.

Since I am using the NES for recording, it seems like I could improve this anyway. I noticed that tapping directly off the CPU audio pins is MUCH better (pin 2 has a faint buzz but it is not near as bad). I found the NES audio path (on the main nesdev site) and noticed it has some funkyness to it. I suspect part of the problem is old / bad components there or some sort of grounding problem.

Long story short, does anyone have any suggestions for making my own audio path? I also have a MidiBox SID and notice that the audio path there is similar. I have also seen designs online that just make use of some resistors off the chip.

The goal is not to fry my precious 2A03 first, and to have better audio as an important second. A third bonus is, if I use multiple outs (one for each pin + cart out for 3 total), I can spend less time recording stuff off the NES since I could do up to 3 channels at a time.

Thoughts?

Author:  cartlemmy [ Thu Jan 13, 2011 9:13 am ]
Post subject: 

Move the NES away from other EMF sources? The TV, fluorescent lights, etc... Though I've never had an issue with any buzz in the audio out on my NES, perhaps your ground wire to the board is loose?

Author:  m00dawg [ Thu Jan 13, 2011 9:16 am ]
Post subject: 

I tried moving it all over the place. It's true I don't have the shielding on but I tried laying it on top, moving it around, etc. and noticed no difference.

I think it's my RF section because the TV picture is also a bit snowy (though that comes and goes) and I have yet to get into the section itself and replace any of the caps.

I certainly won't rule out interference for sure but I tried turning off most everything in my room and still had a noticeable buzz. Note that you might not hear if unless you're looking for it. It's "soft" by listening standards if you are playing games or jamming to tunes. It's just not suitable for recording since I'm mixing other sources in with it, among other things.

Author:  tepples [ Thu Jan 13, 2011 9:19 am ]
Post subject: 

Some of the 60 Hz buzz may be due to crosstalk with the PPU. See my last post about this. To minimize the buzz, set the background color to $0D and turn off rendering while recording.

Author:  m00dawg [ Thu Jan 13, 2011 9:35 am ]
Post subject: 

Aha! That's definitely worth trying! I assume doing that requires either making a custom NSF player or having FamiTracker output an NES binary and then modifying that?

I haven't had to use any dev tools to this point for any of that stuff. Any recommendations on where I might go for more information on that?

Author:  thefox [ Thu Jan 13, 2011 10:06 am ]
Post subject: 

Loopy has released the source for PowerPak NSF player so you could modify it: http://home.comcast.net/~olimar/NES/

Author:  m00dawg [ Thu Jan 13, 2011 10:13 am ]
Post subject: 

Sweet! Well that gets me closer for sure! Thanks guys! It will surely take me a while to figure out how to build stuff and read up on the palette stuff but this marks progress! Appreciate the help!

Author:  NESHomebrew [ Thu Jan 13, 2011 6:38 pm ]
Post subject: 

Would something like this interest you? Seems a bit steep, but if you are into recording it might be worth it for you.

Author:  m00dawg [ Thu Jan 13, 2011 6:51 pm ]
Post subject: 

Oooh maybe! Wish I knew how it sounded though - cleaning up the sound is the biggest issue for me over just amplifying it. I don't think I really need to have one pre-made - I can build and solder things, though it is in a nice and tidy package.

The only problem is that it does not include external cartridge audio. I'll need that too, although I haven't had as many problems with noise off the cartridge pin directly, although I would like to have it be at relatively the same levels. It is sort of optional though - the PowerPak is pretty much just emulating the audio chips much like FamiTracker and I'm not sure which one is better. I sort of like the noise of the cart more but that could all just be in my head.

I tried to see what was going on with the board but couldn't quite make everything out given the pictures :)

Definitely something to consider! I may try my hand at setting the background color tepples suggested. I would imagine it's easy to do but I haven't really dug into what is required. Since that is a cheap(er) fix might as well try it first. Of course, if it eliminates sound, I would imagine continuing with modding my NES would still produce better sound!

Haha something to ponder about...

Author:  tepples [ Thu Jan 13, 2011 7:05 pm ]
Post subject: 

One thing you can do after you've tried the $0D trick is is record a couple seconds of silence before the actual recording to establish a noise profile, and then use Audacity's noise reduction filter to subtract this noise out of the power spectrum of your recording.

Author:  m00dawg [ Thu Jan 13, 2011 8:10 pm ]
Post subject: 

That thought crossed my mind though I'm hoping to use that as a last ditch effort. Using a noise profile could change the sound more than I would prefer, though I have that in my back pocket is all else fails.

Author:  Jeroen [ Sun Jan 16, 2011 5:23 am ]
Post subject: 

From my experience though (not much) it works rather well.

edit: another thing you can do is lift up the video pin and put a switch on it since its the main source of noise.

Author:  m00dawg [ Sun Jan 16, 2011 7:12 am ]
Post subject: 

Jeroen wrote:
edit: another thing you can do is lift up the video pin and put a switch on it since its the main source of noise.


Ah that's not a bad idea. I might try that on the other NES if I can fix it (I think it might be fully dead though - it just emits a loud BUZZ as soon as power is applied :/).

Bypassing the normal audio out totally though would do the same thing, though, would it not? The video out you're talking about, I assume is off the PPU?

Author:  Jeroen [ Sun Jan 16, 2011 8:32 am ]
Post subject: 

that mod linked seems to get the audio from the rf modulator...which will have interference. I would not recommend "rebuilding" the audio path either since it might not sound exactly the same :P (altough yes you could move it out of the way of the ppu)

Author:  frantik [ Sun Jan 16, 2011 11:12 am ]
Post subject: 

if you can, isolate everything from a/c power sources, or get power conditioners

try recording without it plugged into the tv and if you can battery powered laptop and battery powered nes

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