Reverse stereo on Sound Blaster Pro & compatibles

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Reverse stereo on Sound Blaster Pro & compatibles

Postby jesolo » 2016-1-03 @ 09:43

I recently acquired a Sound Galaxy Pro 16 (I38-MMSN812), actually a Reveal SC400 rev.2, but it's just a rebranded card.
In the sound card's diagnose utility, digital sounds are output correct been the left and right channels, but in games that supports the Sound Blaster Pro 2 (digital voices), the sound output is reversed.
Strange that none of my other Sound Galaxy cards (that are Sound Blaster Pro 2 compatible) exhibits this behaviour.
This is the first Sound Galaxy that I've come across that behaves like this.
Is there way in DOS (like a tsr) that can reverse the stereo output?
Last edited by jesolo on 2016-1-03 @ 17:46, edited 1 time in total.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby PhilsComputerLab » 2016-1-03 @ 11:42

AFAIK this is standard behaviour for SB Pro 2. That's why many games have the "swap Stereo" option.

Easiest would be to just swap the leads around, which can be easy with a mixer, but more annoying if you just plug in speakers directly.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby firage » 2016-1-03 @ 13:27

If I recall correctly, SB Pro 1 had reversed stereo and it was fixed with SB Pro 2, but many 'compatibles' remained reversed. And then there's the software which might be reversing things to compensate.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby alexanrs » 2016-1-03 @ 14:55

For software that lists both SBPro 1/old and SBPro 2/new, you can try both settings to see if one of them isn't reversed.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby JayCeeBee64 » 2016-1-03 @ 19:35

I have a Sound Blaster Pro 2 with reverse stereo; I also have a GUS ACE rev 1.0 with the same issue. They're both connected with patch cables to each other and to a Yamaha SW60XG in my Socket 7 PC.

For years I either used the Swap Stereo/Reverse Stereo Channels option in games that had them or just put up with it. Then this thread came along and got me thinking about using cable adapters to correct the reverse stereo issue (I don't have a mixer nor space to keep one around). After looking through Newegg.com I found these:

Image Image

And ended up with this cable setup:

Image

It's not pretty and kinda clumsy, but gets the job done. Most of the time I keep the stereo plugs reversed (R-W and W-R); if I want to go back to original sound I replug them in order (R-R and W-W). This is also done from the GUS to the SW60XG so both the SB Pro 2 and GUS ACE stereo channels are corrected simultaneously.

Of course, this solution is what worked for me; whichever one you choose depends on your needs and what's acceptable for you :happy:

PS: A big thank you goes to soviet conscript and bristlehog for the inspiration. It works like a charm! :-D :blush:
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby alexanrs » 2016-1-03 @ 20:15

Doesn't the "Reverse stereo" issue affect only SFX, with FM music being unnafected?
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby jesolo » 2016-1-03 @ 22:04

Thank you JayCeeBee64 for the advice. Certainly a viable option to consider. I'm just curious as to why this particular Sound Galaxy model has this reverse stereo effect, since my Sound Galaxy Basic 16 (I38-MMSN810) and later revisions (with the AZT2316 & AZT2320 chipsets) do not exhibit this behaviour (for some reason, the AZT1605 chipsets do not support digital playback of the Sound Blaster Pro or Pro 2, only Sound Blaster 2.0).

alexanrs, you do raise a valid point. However, I think that with FM music one wouldn't necessarily notice the difference. It might be a problem with a wavetable daugtherboard connected to the soundcard's Waveblaster connector or, when you plug a stereo source into the Line In of the sound card and route it to the Line Out again.
But, there is nothing more frustrating when you're listing to a demo (like Panic from Future Crew), a MOD file or playing Star Wars X-Wing and hearing the sound effect coming from the wrong direction (I'm now thinking back to 1993/1994). Fortunately, most Sound Blaster Pro/Pro 2 supported games did provide the "reverse stereo" option to compensate for this.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby JayCeeBee64 » 2016-1-04 @ 01:36

jesolo wrote:Thank you JayCeeBee64 for the advice. Certainly a viable option to consider. I'm just curious as to why this particular Sound Galaxy model has this reverse stereo effect, since my Sound Galaxy Basic 16 (I38-MMSN810) and later revisions (with the AZT2316 & AZT2320 chipsets) do not exhibit this behaviour (for some reason, the AZT1605 chipsets do not support digital playback of the Sound Blaster Pro or Pro 2, only Sound Blaster 2.0).


No problem jesolo, it's just a way of resolving this issue. As to why this Sound Galaxy model is the only one, I'll venture a guess of faithful emulation - right down to the swapped audio channels (Aztech probably wised up a bit later and changed their emulation to be more proper).

alexanrs wrote:Doesn't the "Reverse stereo" issue affect only SFX, with FM music being unnafected?


This piqued my curiosity so I went ahead and tried a few quick tests on my Socket 7 PC. What I found was quite interesting.

I configured a few DOS games to play music through the SB Pro 2's OPL3 chip and I got mono output. No stereo FM music. Why I have no idea. The only way to get stereo FM was through DOS music players like Midier.

This probably explains why FM music appears to be unaffected - play Doom's first level and sound effects are reversed while the music seems fine. Play the same tune in Midier and you get reverse stereo FM; I switch the RCA plugs around and the music now sounds as it should.

I probably should try testing more games, but at this point I'll say that the "Reverse Stereo" issue definitely affects both digital and FM sound.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby PhilsComputerLab » 2016-1-04 @ 01:45

Many DOS games have Mono music only.

You got to try later games, such as Spakce Quest V for example. That one has quite nice Stereo FM music.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby alexanrs » 2016-1-04 @ 01:48

For DOOM (and other games using the same engine) you could try running "SET DMXOPTION=-opl3" before running the game. Not sure the tracks themselves are stereo, though.
CD audio should also be affected (and easy to test)
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby JayCeeBee64 » 2016-1-04 @ 03:50

Thanks for the suggestions Phil and alexanrs, will give them a shot when I can. The games I tried were Doom, Descent, Duke Nukem 3D, X-COM, Heretic and Wacky Wheels. For CD Audio I'll try Warcraft II, Descent II and Whiplash (I know how they should play). I'll also dig through my collection to see if I have any late DOS games with FM music.

Doom does have some nice FM stereo tunes. Here's E1M2 recorded from my SB Pro 2 (with correct stereo channels):

https://www.dropbox.com/s/adkn1bobsa1d6 ... 9.mp3?dl=0
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby JayCeeBee64 » 2016-1-08 @ 06:03

Finished testing more games and there's no doubt, all output on Sound Blaster Pro 2 is reversed - digital, FM and CD audio.

While the "SET DMXOPTION=-opl3" variable that alexanrs suggested did allow Doom and Heretic to play FM music in stereo, it was Warcraft, Gateworld and Command Adventures: Starship that made reverse FM stereo really stand out. Gateworld in particular has such a well defined stereo soundtrack that is easy to tell when music starts playing from the wrong channel. It's also interesting that these 3 games use AIL/Miles sound drivers. Descent does have some FM tracks in stereo, but is so slight that is hard to tell when music playback is amiss.

With CD audio, Descent II was the clincher - every music track is in stereo and made it very easy to tell when the channels get swapped. Whiplash and Warcraft II confirmed my suspicions. Of course, all games had sound effects with swapped channels (with the exception of Gateworld, has PC Speaker sound only).

The easiest way to solve this issue is to select the Swap/Reverse Stereo Channels option if available; if not, any of the other solutions suggested (including mine) will do the trick. In the end, whichever one is chosen depends on what the circumstances require.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby PhilsComputerLab » 2016-1-08 @ 07:18

JayCeeBee64 wrote:Finished testing more games and there's no doubt, all output on Sound Blaster Pro 2 is reversed - digital, FM and CD audio.


Well that's good, at least it's consistent!

I would prefer swapping the physical cables to be honest.

Now in games that have an option to swap L and R, like Descent you mentioned, will this swap digital, FM and CD audio?
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby JayCeeBee64 » 2016-1-09 @ 05:23

PhilsComputerLab wrote:Now in games that have an option to swap L and R, like Descent you mentioned, will this swap digital, FM and CD audio?


I was going to answer this earlier Phil but wasn't 100% sure, so I waited until I could try this again on my Socket 7 PC.

Unfortunately, Descent/Descent II only swap digital audio with the option; FM and CD audio stay reversed. I also tried Duke Nukem 3D and got the same result - digital audio was corrected, FM wasn't.

Looks like the only way to truly fix this is by swapping the cables, like you said. Oh well :neutral:
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby PhilsComputerLab » 2016-1-09 @ 05:43

Well, still it's a good outcome. Thanks to your tests we know that "just" swapping the cables gets the job done :)

The next time I play around with a SB Pro 2 compatible card, I better check for this as well.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby alexanrs » 2016-1-09 @ 11:13

I think I have a SBPro compatible card that has reversed stereo for digital sound only, so it can be very useful sometimes.
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby JayCeeBee64 » 2016-1-09 @ 22:19

Here's another possible solution, courtesy of Kris Asick (Gemini000). It comes from his ADG thread; I'll just quote his post here:

Gemini000 wrote:
JayCeeBee64 wrote:Your observation on the SB Pro 2 is dead on - and it's not just the digital audio. FM and CD audio are also reversed (I have tested them myself).

My P120 has that exact same sound card and back when it was still my mother's system, my "solution" to fixing this problem was to just put the right speaker on the left and the left speaker on the right! ;D

That was a long while back though. I stopped using speakers on my computers and started using headphones exclusively around 2007ish. The benefit there is if the stereo's reversed you just flip your headphones around! ;)


Pretty sneaky if you ask me, just switch the speakers if you can; otherwise grab a pair of headphones and flip them. No more reverse stereo :happy:
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby James-F » 2016-10-22 @ 08:52

I want to share me experience for I find this thread misleading especially this statement:
JayCeeBee64 wrote:Finished testing more games and there's no doubt, all output on Sound Blaster Pro 2 is reversed - digital, FM and CD audio.

This is absolutely 100% False, his cables were reversed to begin with.... please read on.
All the SBPro model are NOT reversed, this includes CT1330 and CT1600.

FM/OPL3 plays correctly and can be easily tested with Adlib Tracker 2 where you can actually select Left and Right part of the OPL3 individually and hear yourself.
Line-In is correct, CD is correct, and PCM is also correct.
Doom FM/OPL3 stereo mode is reversed in comparison to the MIDI music, but it does NOT mean the FM output is reversed on the SBPro1/2, its only Doom.

Correct behavior of the SBPro1 CT1330 and SBPro CT1600:
Duke3D, Blood setup the sound will not be reversed when SBPro is selected and the reverse switch should not be enabled.
Descent setup the SBPro WILL be reversed so the reverse switch should be enabled.
Doom, Heretic, Hexen PCM sounds correct when using a SBPro1/2, Doom FM will sound reversed on both (and SB16 for that matter) compared to the MIDI tracks.
The reversal of FM in comparison to its MIDI in Doom is no basis whatsoever to assume that the SBPro has reversed stereo.

If you find this thread on google please disregard JayCeeBee64 posts he probably had his stereo cable reversed or a RCA Red/White cable defect where the colors are reversed.

EDIT:
Corrected missinformation.
Please read that thread for correct SBPro1/2 stereo behavior: http://www.vogons.org/viewtopic.php?f=46&t=50539
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby James-F » 2016-10-23 @ 12:40

Stereo Reverse Chart.png


I have tested PCM stereo all my SBPro2 cards, with the original CT1600 as reference.
Note that all have the FM and CD correct to the Mixer and Line-Out so nothing reversed there.
SBPro1 CT1330 behave EXACTLY the same.

EDIT: I was wrong, the SBPro1 behaves exactly like the SBPro2.
https://www.vogons.org/viewtopic.php?f=46&t=50539
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Re: Reverse stereo on Sound Blaster Pro & compatibles

Postby PhilsComputerLab » 2016-10-23 @ 12:45

One tip for testing your cables. The reason: quite a few cables have the Stereo reversed.

On the 3.5 mm plug you have TRS (Tip - Ring - Sleeve).

Ring, should go to right. Which is easy to remember, as both start with R. On most cabled the red RCA is right, but on some it's the white.

So always test your cables with a multimeter for example.

Image
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