Hello all,
the other day I decided I was fed up with the hum from the audio out on my NES and set about mooching the internet for resolutions.
I found quite a few sites detailing mods to tap the NES audio directly from the chip. However this did require using the Wayback machine and trawling forums...

This mod, for those who don't know, separates the 2 pulse channels onto one output and the triangle, noise and sample onto the other. Its not really 'stereo' but it is certainly beneficial for NES musos.

All credit goes to the original people who did this mod. However I just wanted to save electronics dummies like myself a bit of time and collect all the info into one little guide:

http://www.alone-music.co.uk/?p=681

Like I said, its for noobs, I think anyone with a bit of electronics experience would be able to do this with their eyes closed.
(disclaimer: don't solder with your eyes closed)

I have to say as a big fan of the NES sound, the mod is very very simple and really effective, the hum is gone and having the bass and noise on a separate output makes it easy to get a big fat bass boost on my mixer.

i had just written a big reply with some still active links, but then i checked out your guide and its much better....

thanks so much for doing this! 

i think this was missed, but some of the install pics might help (same hookup points): http://lowgain-audio.com/NESmod.htm

Cheers!
I missed Low-Gains one when I was poking around. I did see the (awesome) product but dismissed it due to its sold out nature. I'll pop a link in though as I would have snapped one up in an instant if they were still available.

Just to be double clear these are the sources I used, I missed out the extra mono tapping and pots as that seemed to me more for people who really care about their games audio, and not music.

http://www.raphnet.net/electronique/nes … mod_en.php

http://web.archive.org/web/200502071827 … tereo.html

http://www.metroidmetal.com/ridley/viewtopic.php?t=7100

great guide!

Great job with the article.  It's certainly easier to follow than the half-assed one I used when I first did this to my NES.
Powerpak users, it's worth noting that you can have a separate output for the expansion audio as well:  instead of connecting Pins 3 & 9 with a resistor, run pin 3 to it's own output (using a capacitor at the RCA jack in the same way as liquidcalm does in his guide.)  Voila!  You have 3 separate outputs.
If you're feeling adventurous, you could also throw in a switch so the expansion audio could be either mixed in with the system output or given it's own output...

Ahh, saw someone post this on facebook. I reposted. Nice job, man.

reminds me that i need to get around to this at some point...would make my midines/piggy work so much easier

I just finished this mod and it sounds awesome. I was feeling adventurous (thanks jmr) and included a switch that separates the expansion audio or mixes it to the standard output with a 47k resistor or turns the expansion audio off all together.

For what it's worth, I went with an op-amp style (Cmoy-inspired) solution. First attempt was using a home-made board but I have now made an SMD version that is a good deal smaller. I like using an op-amp because it would sacrifice itself before you end up doing any damage to your CPU itself (say due to static from plugging in an audio jack or something).

The downside is that it needs power. My first design required a separate power brick but I found a low voltage op-amp from Texas Instruments (Burr-Brown) that can be fed with low enough voltage that I can just use one power brick into the NES and tap off those inputs. That requires using a DC power brick though (the original NES power brick is AC), but a nice clean linear regulated power brick should work just fine, if not better, than the original power brick anyway.

You can see my first attempt here:

http://www.moocowproductions.org/nesa/

Still waiting on parts for my new board so I can't claim success for it just yet.

Hey, does anybody know of any documentation on doing NES audio mods that covers the top-loading model 101? Has anyone done it? I know I've seen it done quite nicely (Crashfaster uses one, for ex.). While I could probably figure it out, it would be great to see a decent shot of the board with the audio out points marked, for example. All I've found so far is "A/V mod" discussions on benheck style sites that pretty much gloss over the issue of audio. The 101 is hard enough to find at a decent price that I'd rather not dig into the thing without some idea of where I'm going first if possible.

m00dawg wrote:

For what it's worth, I went with an op-amp style (Cmoy-inspired) solution. First attempt was using a home-made board but I have now made an SMD version that is a good deal smaller. I like using an op-amp because it would sacrifice itself before you end up doing any damage to your CPU itself (say due to static from plugging in an audio jack or something).

The downside is that it needs power. My first design required a separate power brick but I found a low voltage op-amp from Texas Instruments (Burr-Brown) that can be fed with low enough voltage that I can just use one power brick into the NES and tap off those inputs. That requires using a DC power brick though (the original NES power brick is AC), but a nice clean linear regulated power brick should work just fine, if not better, than the original power brick anyway.

You can see my first attempt here:

http://www.moocowproductions.org/nesa/

Still waiting on parts for my new board so I can't claim success for it just yet.

If you etch an extra of that new board I would buy it from you in a heartbeat!  Also, it might be nice to take advantage of that 4th RCA jack and sum the 3 channels into an extra mono channel.  Great job though man!  smile

I think I have one etched board of my first design somewhere, though it's probably not very good as the first NESA board design was also my first attempt at home etching.

For my newest design, I had the board fabbed with DorkBot and moved most components to SMD. Here is a quick pick of it I threw up on my band's Facebook page.

Dorkbot does boards in groups of 3 so assuming I don't mess up too many times, I should have a spare or two. If you want it, you're welcome to one. Just pay shipping if you don't mind, assuming it's over a few bucks (such as if I need to ship international or something). I'll be out of town next week and I'd rather make sure the design works before giving it out so it may be a little while before I'll be able to ship it out, but otherwise let me know if you'd like one!

As far as the passive mixer, that would have been a really good idea! I think Kitsch mentioned that to me a while ago but for this round I was concentrated on saving space over adding features. A passive mixer wouldn't be very tricky, and in fact would be a pretty good use of the op-amp (to help boost the attenuated signals from the passive mix).  I've added a note on my schematic to add that for the next revision, depending on how this new design works out.

P.S. Kitsch and I have been passing ideas back and forth about this design so he may or may not be working on one of his own, which will probably be pretty awesome so if you're not in any hurry, you might want to see what he comes up with!

Awesome news!  Since it sounds like this project isn't going anywhere I'll wait a bit.  smile

Parts came in so I spent the afternoon populating the board and I'm happy to report that it works just as I had planned! Including my plan to use a DC power adapter so I wouldn't need a separate power source for the op-amp. Works like a charm!

Only thing I may need to work on is changing the resistor value for the cartridge input as it sounds a tad distorted when played through my mixer. I think that's always been an issue. Recording the output directly doesn't seem to be a problem, however (though that could be because I often only record one channel at a time and the distortion is mostly when playing the saw and square channels at the same time).

I also now need some double-sided tape to adhere it to the bottom of the NES case since it's small enough now that it can move around a bit.

So I guess some small todo's but the main concept appears to work. Next up, is trying Theta_Frost's suggestion of having a passive mix out wink

Pics

kineticturtle wrote:

Hey, does anybody know of any documentation on doing NES audio mods that covers the top-loading model 101? Has anyone done it? I know I've seen it done quite nicely (Crashfaster uses one, for ex.). While I could probably figure it out, it would be great to see a decent shot of the board with the audio out points marked, for example. All I've found so far is "A/V mod" discussions on benheck style sites that pretty much gloss over the issue of audio. The 101 is hard enough to find at a decent price that I'd rather not dig into the thing without some idea of where I'm going first if possible.

I've done it to a top loader. The mod is exactly the same.

justinthursday wrote:

I've done it to a top loader. The mod is exactly the same.

Er, yes - but where are the audio outputs on the board? smile