Stereo audio output from Cave SH-3 based hardware?

[bitkid]

I was wondering if there was any possible way to get a stereo audio signal out of the newer Cave SH-3 based hardware. I was listening to the DFK BL OST today and noticed that it is all composed in stereo. Do the SH-3 boards actually process the audio (or even just the music) as stereo or is it all strictly mono? It just seems curious to me that the OST recordings would be stereo when the game hardware doesn't even seem to support it.

[yosai]

The sound chip on SH-3 boards is a Yamaha YMZ770C-F. Looking at the data sheet it outputs analogue audio on pins 3 (L) 4 (R) and 5 (Gnd) You could try and tap in to these but it's probably not a very good idea.

[Artemio]

I was intrigued by this, and not only in SH-3 boards. I started by checking out the ESP.RA.DE. and Guwange boards, and after identifying the Yamaha chips, including the DAC and Opamps they indeed supports stereo audio, they even have the lines wired.

However, the audio is not stereo. Emulators report it as stereo and the chips support stereo, but after recording both channels and comparing them it results they are identical, at least from MAME. This includes SH-3 and 68000 based hardware. I didn't want to take out the soldering iron and risk damage to the boards without knowing it the stereo signal would be indeed stereo or just dual mono.

I trust the results since MAME emulates the sound chips, and the chip outputs a single bitstream that alternates between channels digitally, which the DAC later converts to dual analog.

[emphatic]

It would be cool if someone would manufacture a hardware that you can "clip on" on top of the DAC before the amplifier on the PCB to at least get a low level audio output. I have 2.1 speakers with line in for my cabinets and being able to bypass the PCB amplifiers would be awesome.

[p1pkin]

I trust the results since MAME emulates the sound chips, and the chip outputs a single bitstream that alternates between channels digitally, which the DAC later converts to dual analog.

Well, do not trust MAME too much Current YMZ770 emulation does't have PAN implementation, i.e. all samples plays to both channels with the same volume.
Also, all SH3 games do not use stereo-features - all samples plays with the same PAN, so even if someone solder stereo AMP inputs directly to L/R outputs of YMZ chip where will not be any stereo, both channel will be the same.

emphatic
I am not sure you'll get better sound this way. Cave uses highly compressed samples with very low bitrate, as result it sounds like frog's ass at mid to high frequences. Using filters on PCB they hide such low quality, but connecting directly to YMZ you'll get sound "as is".

[bitkid]

I’m starting to familiarize myself with the MAME CV1K code base and surrounding modules, as well as Buffi’s ck1k_research repo, with the goal of attempting to inject higher bitrate and possibly even stereo audio into the ROMs. I’m going to start with seeing if I can just get higher bitrate audio to work first, as that seems like the easiest first step.

It’s funny that this post showed up near the top of the Google results when searching for “Yamaha YMZ770”. I had completely forgotten I’d posted this over 10 years ago, before I knew how to program or even how the underlying hardware worked in any way shape or form. It was a surprise to see my handle pop up.