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SB16 DAC mod - has anyone done this before?

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commodorejohn

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So I've been playing around with my 486 and its SB16, and while I'm pretty happy with it, one thing that I've noticed is that the SB16 audio is noisy as all-get-out - there's basically an AM radio hiss even when nothing's playing. This isn't too big a deal for the digital sound, as not much from that era is particularily high-fidelity to begin with, but it's rather disappointing to have all that line noise on my lovely, lovely real honest-to-God OPL3 music.

But one thing I do know is that the OPL3 produces digital output and requires a separate DAC - so I've been thinking that it should be possible to wire up a separate replacement DAC outside the case, away from all the interference, and enjoy crystal clarity. Datasheets for both the chip itself and Yamaha's compatible DAC are available online, so I don't see why this couldn't be done.

Only problem is, low-level hardware stuff is anything but my forte. I'd like to see this done, but I don't have the knowledge or the skills needed to do it myself. I'm just kind of wondering if anybody has done this in the past, or has an idea how to go about it?
 
Creative's AWE32 cards come equipped with an S/PDIF header, if you want to save yourself some trouble. The digital output is actually that of the EMU8000, to which the OPL3 is connected, and with which reverb/chorus/EQ can be applied to the signal. It's actually a pretty decent way to go. I made some recordings comparing the output from the onboard DAC, an external DAC, and a straight digital capture, if you want to hear the difference:

http://queststudios.com/smf/index.php?topic=2416.0

Be aware that not all AWE32 cards are created equally. The cards bearing the CT1747 chip (CT2760, CT3900, CT3980, etc.) integrate an actual Yamaha OPL3 FM core, while a number of the later cards (and AWE64 variants) use Creative's "Quadrature Modulation," or CQM, technology. Whether that's actually important or not is a matter of personal preference.
 
What model of sound blaster do you have? Some of them are much less noisy than others.

To be honest between the noise and the hanging note bug, I just decided to forget about sound blasters, I'm using a Yamaha YMF719 based card now and it sounds very clean.
 
You can buy a simple D/A. Many are in the thousand dollar range, but they go for under an hundred too. This one from Full Compass looks workable. I've bought various audio equipment from them a few years ago and they were a good company to deal with.

You mentioned that electronics wasn't your forte, but in case you get adventurous then Rod Elliott at ESP has what is probably the simplest circuit you'll find, including a TTL to COAX converter. Just for the fun of it, here is a circuit from Uwe Beis for a very high quality converter (and a recipe for Thunfischnudelauflauf!), but it will probably require a couple of hundred dollars worth of parts (so maybe just stick with the tuna casserole). Of course you'd end up with a unit that was worth many times that.
 
just a thought but some sb16 had a jumper for amplfied output. perhaps you are hearing that.
 
I think some people would record directly out of the OPL3 chip's outputs on the SB16.
SB16s have a lot of noise, much like CD drives. That annoying fuzzing coupled with a bit of a ring.
Thankfully I have one of my SB16s directed into the silent onboard audio of my computer. So I can mute/unmute the SB16 however I please.
With two soundcards, cool stuff happens.
 
Back in the day we had a ghetto fix for dealing with that -- give the card it's own faraday cage. Get some thick (3-4mil) plastic, some 3m spray adhesive, and some heavy duty aluminum foil. Laminate the foil between two sheets of the plastic, fold it around the card, and take a bare corner of the foil and attach to ground.

Though if you're talking the OPL3 sound, there is no such thing as 'clean' output from that steaming pile of... ( I NEVER understood what made adlib/FM so popular -- it sounds like ass even compared to CMS or tandy sound!)
 
deathshadow said:
Back in the day we had a ghetto fix for dealing with that -- give the card it's own faraday cage. Get some thick (3-4mil) plastic, some 3m spray adhesive, and some heavy duty aluminum foil. Laminate the foil between two sheets of the plastic, fold it around the card, and take a bare corner of the foil and attach to ground.

Though if you're talking the OPL3 sound, there is no such thing as 'clean' output from that steaming pile of... ( I NEVER understood what made adlib/FM so popular -- it sounds like ass even compared to CMS or tandy sound!)
Click to expand...
Hey, OPL2/3 is a very capable chip - the problem is that hardly anybody ever made good use of it, outside the demo/tracker-scene (and even that didn't get its best examples until years later.) Check out "Oskari Leads the Investigation," for example. If more games had done stuff like this, the OPL chips wouldn't have such an undeserved reputation for being shoddy.
 
deathshadow said:
Back in the day we had a ghetto fix for dealing with that -- give the card it's own faraday cage. Get some thick (3-4mil) plastic, some 3m spray adhesive, and some heavy duty aluminum foil. Laminate the foil between two sheets of the plastic, fold it around the card, and take a bare corner of the foil and attach to ground.

Though if you're talking the OPL3 sound, there is no such thing as 'clean' output from that steaming pile of... ( I NEVER understood what made adlib/FM so popular -- it sounds like ass even compared to CMS or tandy sound!)
Click to expand...

OPL3 has a very unique sound, particularly due to its use of sine waves, and the "sine-tooth". It's very similar to its bigger brother the Yamaha DX7.
YM3812_waveforms_numbered.png

I also just love the percussion on it.

I love sitting in a dark basement room listening to dune 2. It should be played on an MT-32, but still sounds nice with OPL3.

--> I think it's something that takes some time to get accustomed to. My ears prefer a particular OPL3 variant. I actually just run both at the same time, makes the sound more rich anyways. There's little things I like about all variations.
 
commodorejohn said:
Though if you're talking the OPL3 sound, there is no such thing as 'clean' output from that steaming pile of... ( I NEVER understood what made adlib/FM so popular -- it sounds like ass even compared to CMS or tandy sound!)
Click to expand...

No, it's just crappy musicians :) Try this perhaps:

http://www.exotica.org.uk/mediawiki/index.php?title=Special%3AModland&md=search&mod=body+blows&aut=&for=ad+lib&col=&ins=

I'm sure you'll find a way to play it. I don't say you have to like it... But at least you can say if it still sounds like an ass ;)
 
For decent OPL sound I can recommend trying a Sound Blaster Pro 2.0.

They are rather quiet compared to the Sound Blaster 16 cards. The AWE64 GOLD is also quiet, but doesn't have the OPL3 chip; It comes with a Creative clone and sounds different. But that card is great in combination with MIDI.
 
michal said:
But at least you can say if it still sounds like an ass ;)
Click to expand...
It does... tinny, weak, frequency distortion - everything I expect out of an FM synth. MAYBE I got spoiled by having access to a CZ-101 and TR-909 before Adlib was even a twinkle in Martin Prevel's eye... but to my ears the sounds from Yamaha FM synths have always been like nails on a chalk-board at best...

Hell, I think C/MS / game blaster sounds better as at least it's output is kind-of clean without that annoying tinny 'buzz' that makes every instrument sound like a shamisen or bouzouki.

Unless of course you actually like the shamisen and or bouzouki... to me both instruments are just ear-bleeding annoying.

MouseBender: SHUT THAT BLOODY BOUZOUKI UP!

I suppose if all you want is music that's nothing but sitar, shamisen and bouzouki, Adlib does a decent job of it (like that 'body blows' file)... you want mainstream string instruments, drum and piano -- much less woodwinds, horns or organs, you're **** outta luck.

Gah, adlib drums -- makes me want to punch whoever thought those chips were suitable for doing percussion.
 
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deathshadow said:
Gah, adlib drums -- makes me want to punch whoever thought those chips were suitable for doing percussion.
Click to expand...

Yeah, one reason why I hated FM. Hearing the IIgs's Ensoniq or the MT-32 with real percussion was enough for anyone to crave something wavetable. It also didn't help that composers wrote their music with a real synth in mind, and Windows didn't do it any favors with its driver's General MIDI mapping. The best music is always going to be the stuff composed specifically for FM. For General MIDI, the best thing you can do is install Windows 3.1x and use Voyetra's SuperSAPI! FM driver with its 4-operator instruments... still has crappy drums, but its sounds WAY better then the generic Microsoft driver.
 
Cloudschatze said:
Creative's AWE32 cards come equipped with an S/PDIF header, if you want to save yourself some trouble. The digital output is actually that of the EMU8000, to which the OPL3 is connected, and with which reverb/chorus/EQ can be applied to the signal. It's actually a pretty decent way to go. I made some recordings comparing the output from the onboard DAC, an external DAC, and a straight digital capture, if you want to hear the difference:

http://queststudios.com/smf/index.php?topic=2416.0

Be aware that not all AWE32 cards are created equally. The cards bearing the CT1747 chip (CT2760, CT3900, CT3980, etc.) integrate an actual Yamaha OPL3 FM core, while a number of the later cards (and AWE64 variants) use Creative's "Quadrature Modulation," or CQM, technology. Whether that's actually important or not is a matter of personal preference.
Click to expand...
Well, I wound up sending off the SB16 along with the rest of the computer to someone else, but now I've got my tax return, I think I'd like to grab an AWE32 for my Pentium system ;) I have a very nice sound card for another computer of mine that has S/PDIF input and clean, high-quality analog output, so I can run it through that. Is there a guide to which cards include the actual OPL3 core and S/PDIF headers?
 
I'm looking at getting an AWE32 CT3670, but before I go dropping money on that I want to make sure it's got the actual OPL3 core and not the CQM core; I've had too many annoying experiences with "compatibles" that are just different enough to botch the sound on some song or other completely. I'm told that the CT1747 chip is the one that has the OPL3 core, but the chip the seller sees on the board is CT1745A - does this mean it doesn't have it?
 
It just kinda hit me like a light-bulb, couldn't you just use a ground loop isolator, like used in car stereo's to remove alternator whine?

I know its a bit late , but better late then never! :D

BTW, the CT3900 also has the newer CT1745A-S mixer chip... the CT1745A-TBP was actually put on the cheaper AWE32/64s, whereas the former was put in the original AWE64 Gold... but both the outputs are much cleaner than the older SB16 mixer chips. All awe32/64 are wavetable cards, not true OPL3. You are correct that the cards you want must have a CT-1747. Its not an exact copy, but nearly identical to yamaha OPL3 , with addition of a integrated bus controller.

CT-1740, CT-1750, CT-1770 are TRUE OPL3 SB16 cards. Hope this helps. :)

Now , if my noggin serves me correctly, the awe32's without real OPL3 , have an empty spot for the YMF289 on the circuit board. All you have to do is solder it on. I also seem to recall it being a workaround for the hanging note bug using the waveblaster connector, if you wanted true yamaha sound. The bug seems to be with the wavetable header itself, not support for OPL3, due to it sharing the header with the midi port. =)


Personally , if it was me, and I was just going to buy a card , I skip sound blasters completely, even though I am a collector of them (think I am up to 13 diff ISA models atm!). I find a PAS16 or GUS16, and pair it with a SBPRO 1. That way you have real stereo OPL2 and OPL3, and no rice krispies! (snap-crackle-pop) ;)

Dont forget the 3.5mm patch cord. Put the output from the SB into the line in of the PAS16/GUS16 if you decide to go the 2 card route. I seem to recall the volume of the SB should be about 65%.
 
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The PAS16 is indeed shielded very well. It basically has no "computer talking" noises. However the two cards I have do have a constant hiss. It's not loud really, but it's there.

The other thing is that the Thunderboard / Sound Blaster part is compatible to Sound Blaster only. So no Stereo. But many games support the PAS16 natively. Space Quest 4 for example with beautiful Stereo FM :)
 
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