SNES rebuilt audio dac circuit

This's something I slapped together for fun. A friend of mine kept raving about how the snes spdif digital audio mod sounds way better than the analog from the console. Since I don't have any spdif or digital hardware I didn't bother with the mod for a long time. Then I heard an actual recording of the digital audio compared to the default analog and it is indeed superior sounding.

So I went out and got the parts and did the digital audio mod. I bought a cheap ebay spdif to analog converter to test that it works. Everything works fine, at first I had this hissing noise but today I sat down and fixed that. The spdif getting converted to analog using the ebay converter does indeed sound different:

http://www.youtube.com/watch?feature=player_embedded&v=smpUQsj6Ioc

I prefer the new audio circuit but it's really up to personal preference. The snes by default has a lot of muffle so this's a mod that can help a little bit with that.

Also tiido was nice enough to point out that the digital audio signals in the snes are i2s standard. I tried using a straight i2s to analog chip to skip going to spdif and back. It works I can hear the audio but the output is majorly distorted. Oh well.

While I can understand some video mod to get better video quality without creating other issue (like those NES RGB mod erroneous palette), I have trouble understanding all those other crazy stereo/digital/whatever audio mod for retro console trying to fix non-issue IMO. The thing sound almost the same to me except that the unmounted SNES audio seem to have better bass. Then again if you think it sound better I'm glad it worked for you.

I'd appreciate high-quality (44kHz, 16-bit) lossless (i.e. WAV files compressed with zip or rar or whatever) audio recordings of actual games (try Actraiser!) rather than Youtube. The audio codec in Youtube videos is highly compressed, even at 720p and higher. Otherwise I can't tell any real difference, and that's certainly due to use of Youtube.

After I make the two recordings match stereo (one's reversed) and match phase (one's inverted) and normalize the volumes to match, I'm having the worst time actually distinguishing the two versions... I can't hear it. I can't even see it in a spectrogram.

If I do take the original recordings, match phase to the sample, and have the two recordings cancel each other out, there's a residual that seems to be mostly from ~3kHz to ~10kHz... It's awfully subtle though.

Yup 480p at Youtube doesn't cut it. Also I believe YouTube also applies some sort of compression (referring to dynamic range compression, the audio "effect", not data compression) to the signal.

I made another video, this time with the stereo sound matching in both parts haha:

http://www.youtube.com/watch?v=i9KKwunk1sI&feature=youtu.be

Are you expecting 44.1 kHz and getting the slightly above 32 kHz that the Super NES puts out?

One thing causing the characteristic muffle of Super NES audio is that decompressed samples are strongly low-pass filtered during Gaussian interpolation. In order not to sound muffled, a track needs to include some fairly strong pre-emphasis in its drum samples.

Again according to tiido interpolation is done in the snes chip so nothing can be done unless you want to recreate the chip somehow. As for the khz thing, beats me I just built this to see if it sound different which it does.

I know. The pre-emphasis I speak of is an equalizer effect applied just before the BRR sample data is created. So one would need to replace the game's or SPC file's BRR samples with remastered samples.

IMO, the main point in doing these mods is to get as clean a signal from the machine as possible without electrical noise from the other bits getting in the way. For machines like the SNES, Saturn, Dreamcast and others that work with standard digital interfaces inside it's trivial to break out a clean signal before the video gets a chance to sit on it. For machines that don't like the NES we can take the audio from as close to the source as possible and re-implement the mixing circuitry with proper shielding and isolation. For machines like the C64, we can go one step (well ok, two steps) further and provide the hardware with its own regulated power supplies and provide isolation on the address and data lines.

The bus noise inside the C64 is so bad sometimes that at least one demo has proven that the C64 can play music without the SID inserted: Vicious Sid 'No SID' Part

I did the SNES S/PDIF mod just the other day and was thinking about what you did. Instead of using a crummy eBay DAC, why not just save that step and do it yourself internally? You got distortion, but I say don't give up, keep at it and try to find a DAC that'll work. I'm willing to bet most people don't have a digital audio option, and thus don't care about S/PDIF, but if you could "upgrade" the DAC internally and get a noticeable improvement then I bet a lot of people would be interested in that. Perhaps try a different D/A, or keep the S/PDIF mod with the CS8406 and then find an IC that'll convert one of its standards to analog.



I'm not replying to just you, SkinnyV, I'm just continuing on what you said.

What I can't understand is why so many people hunt for the best video quality and ignore audio quality completely. I'm speaking in general, not just in the video game realm. But how many people know some one that went out a bought this huge 1080p cutting edge million refresh rate TV, but only listen to it through the TV's speakers? Most TV speakers are just complete garbage. That kind of thing boggles me. It only makes sense to balance your better video quality with better audio quality.

Not that I'm defending the NES "stereo" mod. I really don't see the point of that. It's stereo in the sense that different sounds come out of the left speaker than the right, but that's not really what stereo is about. NES games aren't programmed for stereo, so you don't get actions on the left side of the screen coming out the left speaker and vise versa, panning from left to right and right to left, stereoscopic music, et cetera. What you get is something that was intended to be mono broken up into stereo, which would have a negative outcome IMO.

But as for the SNES S/PDIF mod, I'm very happy with it. I recently got a new AV receiver with digital audio inputs, so I was eager to get digital audio from my SNES. I set it up so I could switch between analog and digital to compare. I'll admit, at first the only thing I noticed was digital was a little louder. But after listening to a few different things, the difference is definitely there. And I don't have the greatest setup in the world. Not that there was a "problem" with the SNES audio, but digital is just better. Everything is a little more clear. Highs and lows, especially lows, now appear to be muffled on analog. While listening to music from games, there's more separation between parts (I guess you could just say it's more clear), and overall there's better stereo separation.

A YouTube video might not be the best way to evaluate the difference. Especially since this one converted the digital to analog before recording. Is the improvement HUGE? I think the average person wouldn't notice much difference. That's not to say I think I'm better than anyone, or I'm some huge audio nut. I've just noticed that people more easily notice improvements in video but not so much in audio. But it's definitely a decent improvement nonetheless. And at least with digital you don't have to worry about interference.

Anyway, that's just my thoughts on the matter.

Maybe you guys should upload a FLAC comparison somewhere as I can't hear what you guy seem to talk about and I find the un-modded audio in the youtube video Drakon posted better sounding than his modded circuit. But then again I might have a bad hear for those thing.

Well, like I said, Drakon has the digital audio being converted back into analog. Others have said YouTube isn't the best for audio comparisons because of compression. So those two things combined, it isn't the best thing for you to evaluate how the S/PDIF from the SNES can sound.

I really wouldn't mind making some recordings, but I do not have S/PDIF on my PC. Hmm, well I might have S/PDIF out, but not in.


Another thing I just remembered, regarding the benefits of digital audio, is the lack of a hum. Some people get a nasty hiss with analog audio, which is completely absent with digital.

I did some playing with the system today. Some games I can hear the difference (it isn't huge), other games sound the same. What I really wish would be a way to remove the interpolation.

As for audio upgrades there's a lot of possibilities out there. Thanks to the help of ace on sega16 I learned how to tweak the low pass filter on the audio circuit of the model 1 sega genesis. I can now set the model 1 genesis audio circuit so high I hear distortion that's normally filtered out, and I can set it so low it sounds like the music is being played through a wall. I'm just waiting on caps to set it how I like, some games sound too muffled so it's a good thing to do. With the famicom the upgrade kits I use from japan work, however they only sound right on the av famicom which is a bit of a shame. Regarding the whole nes stereo separation thing it's really easy to mix the two channels together if you don't like the effect, I just set my amp to mono output on both speakers. I've been trying to improve my gaming audio experience since I was 13 and my dad gave me his old 1979 pioneer amp (which is still what I use today).

Well if you're gonna mix it back into mono anyway, then what's the point of the separation in the first place? I'm not asking in a sarcastic way, I'm just wondering if there's something I missed. Is there some kind of quality improvement if the sound channels remain separate until they hit the amp? I would think, no, there isn't. And if there is, it would just be a very, very small improvement in clarity. Or am I wrong?

Ahhhhhhh! That puts it all into perspective now. It's basically for headphone/really good stereo listening, where you want to hear silence when the game is doing silence, and no background hiss or 60 Hz buzz behind quiet passages. Please excuse my previous critique as if it were going to improve general sound quality in a normal environment.


I have noticed that emulators have taken longer to get audio up to par than video as well. On machines that only output composite video, it's partly because composite video is equivalent to phone-quality audio, whereas RCA can be equivalent to between S-Video and RGB quality (significant video noise on audio is due to design quality, not an inherent limitation of RCA audio). On RF-only machines, people have done more audio mods to get line out.


Could you have achieved the same with an equalizer, upping the sliders on the low and high end? I bet if you put one in, you could make this digital signal sound even better. I'm skeptical about better stereo separation. That implies either a poor amplifier in the SNES that leaks noticeably between channels, or intentional mixing.


There is if you use an audio op-amp as opposed to a CMOS digital inverter configured as a linear amplifier via a feedback resistor, as the NES does internally.


The digital audio isn't objectively better; it's different, which some people prefer. So not hearing it as sounding better isn't an indication of poor hearing skills, it's just an indication of different subjective preference.

Well I mean, TVs don't have S/PDIF inputs (at least not the ones I've seen!) so generally the only people that are gonna wanna do this are the ones that have a decent sound system.



No, an EQ would not achieve the same thing. It's an actual improvement. The highs and lows are not simply louder. I don't know a great deal about this stuff, but it is my understanding that signal degradation and inference will cause the highest and lowest frequencies to be effected first and possibly lost. The digital audio output will remain intact, at least from the SNES to the receiver, so it wont suffer from signal loss and interference like analog will. For that reason, the highs and lows are just better quality. And possibly, the highest highs and lowest lows are present whereas they are missing in analog. If you boosted the highs and lows on the analog output, it would probably sound worse. Being that the high and lows are effected by interference, boosting them will just be boosting the frequencies most effected by interference. Furthermore, boosting just the highs and lows gives you that generic "club" smiley face EQ that I don't care for at all. It's not the way anything should be EQ'ed IMO.



Well again, SkinnyV was listening to Drakon's samples, where the digital audio was converted to analog before the recording. It's not at all a true test of what the digital audio sounds like.

I would argue that the SNES digital audio is better, and not just different. Now I almost wanna get an S/PDIF input for my PC. If I had one, I could record samples of both and analyze them for a true evaluation.

The only difference I've heard between the two Youtube videos is that the "stock" circuit sounds like it has some kind of filter on higher frequenices (maybe a low-pass filter?) -- the result is that the audio sounds "dampened". The new/modded circuit appears to have none of that -- or if it does, it's configured/tuned to be less severe. But this is not an effective way for me to conclude anything, because the audio on Youtube is highly compressed (regardless if 480p, 720p, or 1080p) and lossy.

There are also folks here on this forum who have written audio emulation libraries and are quite familiar with waveform analysis who can provide a full explanation of what's truly different, but only if good, clean, lossless recordings are given.

So again, politely, please stop using Youtube for this -- give us 44kHz 16-bit stereo .WAV files (you can compress them with zip/rar, which are lossless), preferably of a game that has good range and that folks are familiar with and can compare against existing games (I mentioned Actraiser for a reason). You can upload them here on the forum as long as they're smaller than 4MBytes. If you can upload audio to Youtube, then you obviously have the audio in a digital format (I do not care if it's "recorded onto an analog device" or "going through analog cables" (i.e. RCA or 1/8" stereo jacks) as long as both the "stock" output AND the new/modded circuit output are recorded via the same cables/means). So please provide what you have! :/

It'd be great to have some 32 kHz bit-perfect recordings of the SNES, rather than something that's been upsampled to 44.1 kHz or 48 kHz.

It's nice to have them separated because a lot of people out there like it that way. I personally don't use it but all my clients always say how happy they are with it.

The reason why I prefer this new analog circuit is because I hear a little more range of audio that used to be muffled out. With the snes going to spdif and then back to analog you can hear more highs (and probably more lows), there's just less muffle, it could be better but any improvement makes me happy. The whole point of doing this was to prove that even converting the digital audio back into analog using a cheap ebay converter and then filtered through youtube still sounds better than the regular analog.

As for high quality recordings I'm not sure this mod is a big enough improvement to bother putting it under that large of a microscope. Also the spc players on my snes powerpak doesn't like the actraiser spc files.

What we're saying is that the difference is so subtle that unless you're in ideal listening situations (IEMs, silent room, all variables compensated for), I'm not convinced the two versions would pass an ABX test.

Maybe later if I get time haha.