tpowell.ca wrote on 2023-01-06, 19:43:

That said, the output of the Yamaha really impressed me in Windows Sound System emulation mode but the real winner to my ears is the ESS688 with the cleanest sounding SBPro emulation.

WSS could technically go up to 48 KHz so it might sound a bit cleaner than 44.1 KHz cards in certain cases. I remember Turrican 2 being one of the rare DOS games which actually allows you to pick that sampling rate in setup, when using a WSS compatible card.

Out of curiosity, does your YMF719 card have two oscillator crystals on the PCB or just one? I think I might have the same model, as pictured here.

Considering that I own a SBPro2 CT1690, I can confirm that the sound quality with sample rates above 11 kHz isn't impressive especially when the low-pass filter is enabled, causing it to get muffled. The lack of a dedicated line-out connector also has a factor on this, although the speaker out connector can be tweaked to get an approximation with the wheel.

Another thing, enabling the stereo DAC doesn't necessarily disable the low-pass filter as you described. Due to the lack of a proper low-level documentation for Sound Blaster cards at the time, many developers weren't aware the bit values used for toggling the output filter and the stereo DAC were located on the same mixer register.

About the ESS sound card, I'm not surprised given that it was the only clone manufacturer that bothered to prevent aliasing in SBPro mode.

For the Yamaha sound card, there is a mod by James-F to get that low-pass filter effect in SBPro mode. Perhaps you have likely read it.

Joseph_Joestar wrote on 2023-01-06, 20:20:

WSS could technically go up to 48 KHz so it might sound a bit cleaner than 44.1 KHz cards in certain cases. I remember Turrican 2 being one of the rare DOS games which actually allows you to pick that sampling rate in setup, when using a WSS compatible card.

Out of curiosity, does your YMF719 card have two oscillator crystals on the PCB or just one? I think I might have the same model, as pictured here.

The source material was a 44100Hz FLAC file, so playing at 48kHz would actually degrade audio quality due to resampling in this instance.
You are correct, that card is the exact same as mine.

Gmlb256 wrote on 2023-01-06, 20:24:

Another thing, enabling the stereo DAC doesn't necessarily disable the low-pass filter as you described. Due to the lack of a proper low-level documentation for Sound Blaster cards at the time, many developers weren't aware the bit values used for toggling the output filter and the stereo DAC were located on the same mixer register.

For the Yamaha sound card, there is a mod by James-F to get that low-pass filter effect in SBPro mode. Perhaps you have likely read it.

From back in the day when I was learning to program sound on my SBPro, I'm quite certain that as soon as you call for the card to play back samples in stereo, the mixer would automatically disable the filter.
I had made a TSR so I could te-enable it within games and demos and that worked.

For the Yamaha card, you are right. I even modded the card to fix the low pass filter, but for some reason I was unable to toggle it.
Not sure why.
I'll have to recheck my setup.

Thanks

Gmlb256 wrote on 2023-01-06, 20:24:

About the ESS sound card, I'm not surprised given that it was the only clone manufacturer that bothered to prevent aliasing in SBPro mode.

OPTi cards have a low pass filter in SBPro mode, if that's what you mean.

I don't have a real SBPro to compare it to, but it sounds pretty nice in older DOS games. Possibly not quite as smooth as on my ESS 1868F but still reasonably close.

Joseph_Joestar wrote on 2023-01-06, 21:07:

Gmlb256 wrote on 2023-01-06, 20:24:

About the ESS sound card, I'm not surprised given that it was the only clone manufacturer that bothered to prevent aliasing in SBPro mode.

OPTi cards have a low pass filter in SBPro mode, if that's what you mean.

I don't have a real SBPro to compare it to, but it sounds pretty nice in older DOS games. Possibly not quite as smooth as on my ESS 1868F but still reasonably close.

Interesting, I never heard of any sound card with OPTi chips having it implemented in SBPro mode.

Gmlb256 wrote on 2023-01-06, 21:51:

Interesting, I never heard of any sound card with OPTi chips having it implemented in SBPro mode.

My OPTi 82C930 card has it. I was doing some tests on it today when I noticed the filter. It seems to be on by default, in SBPro mode.

This became very apparent to me since I had been using an (unmodified) Yamaha YMF719 card right before that.

Joseph_Joestar wrote on 2023-01-06, 22:19:

Gmlb256 wrote on 2023-01-06, 21:51:

Interesting, I never heard of any sound card with OPTi chips having it implemented in SBPro mode.

My OPTi 82C930 card has it. I was doing some tests on it today when I noticed the filter. It seems to be on by default, in SBPro mode.

This became very apparent to me since I had been using an (unmodified) Yamaha YMF719 card right before that.

The SBPro examples that you provided sounds quite close to the real thing with the low-pass filter enabled, including the description of getting lower quality sound (it also happens when selecting Sound Blaster Pro) with the three mentioned Epic games without the fixes.

Added the OPTi 82C929A card.
This card is even more impressive than the ESS688 as it has a genuine Yamaha OPL3 synth (like the ESS688) but adds Windows Sound System support.

Added the Orpheus 1 card with the Crystal CS4237B chip.
As expected, superbly clean output in both SBP and WSS modes.

Like most chips (ESS, OPTi), it uses a variable lowpass filter when playing back digital audio below 44.1kHz to minimize aliasing.
It also correctly sets the channels in WSS and SBP modes.

I have not included an audio sample yet in any youtube videos.