Digital Audio on Turbo Duo - Is this possible?

[Duo_R]

With so many Digital Audio mods popping up, I wonder if this is a possibility for our Duo? Would this bypass all the sound issues that we are having or would that not help? Any ideas how this mod would work on a PC Engine / Duo?

[SignOfZeta]

I'm pretty sure this isn't possible since there is probably no digital sound signal external to the chip on a PCE.

[Duo_R]

so my next question is can we yank the existing sound amp, and build our own for the sound issues? Does anyone have details on the sound chip and amp for the duo? I cannot find any technical docs.

[Michael Helgeson]

It would be possible, but it wouldn't improve the actual audio any really, nor would it fix the cap issue that causes the original problems. All they do is simply adapt the analog source to digital. The same mod can be done to other old game systems, and older laserdisc players that don't originally have digital output via toslink or coaxial out.

[Michael Helgeson]

so my next question is can we yank the existing sound amp, and build our own for the sound issues? Does anyone have details on the sound chip and amp for the duo? I cannot find any technical docs.

You need to keep in mind that its not really the amp at fault, nor the chip, but actually just caps drying out in most cases.

[Duo_R]

I have replaced more and more caps, so I am beginning to get nervous that it won't fix...the amp is next on my list if this doesn't get better!

[Michael Helgeson]

I have replaced more and more caps, so I am beginning to get nervous that it won't fix...the amp is next on my list if this doesn't get better!

You prob need to get a meter out and start back tracking. Until you do your just making wild guesses.

[Duo_R]

any suggestions on how to test? I have a multi-meter, would that work or do I need to get a capacitor tester (forget what they call it).

[ceti alpha]

It seemed nat had a similar problem with my Duo. He replaced every cap to no avail. He finally found the culprit though. Here's the description nat posted in the Duo Sound Fix thread a while ago:

"Speaking of the sound issues, I recently discovered a cap elsewhere on the mainboard outside of the op-amp cluster is directly linked to certain sound issues. Specifically, if you are having problems with all of the following: ADPCM sample playback, PSG, and redbook. The cap in question wasn't previously known to be part of the audio circuit at all and I have a feeling is the culprit in the cases where replacing all that caps in that circled area and to the right of the circled area don't fix the problem.

You have to remove the FCC shielding to even see this cap. It's kind of in the middle of the board, out in no man's land by itself. Like the component I discovered to be responsible for video failure on the TurboExpress, this is another innocuous little guy you'd never suspect. I'll post a picture up in the next couple of days that shows where to find the little rascal."

[Duo_R]

yeah, I will check my board to see, but does anyone have pics of the culprit? I am doing the shotgun approach right now, when I would prefer a sniper rifle with scope...

[ceti alpha]

yeah, I will check my board to see, but does anyone have pics of the culprit? I am doing the shotgun approach right now, when I would prefer a sniper rifle with scope...

I don't know if nat posted a pic of the culprit, and he's away on vaycay right now. 

[Duo_R]

I see a 100uf capacitor in the middle of the board, but there are some other caps in that general area (smaller). We will see, I got 10 100uf caps on order from the place that is shipping my HOP-M3.