FM and PCM Volume Balance of SB Cards

Discussion about old sound cards, MIDI devices and sound related accessories.

FM and PCM Volume Balance of SB Cards

Postby James-F » 2016-8-29 @ 07:58

Many newer DOS sound cards including SB-Pro to SB16 and their clones have a software mixer that allows the user to change the balanced between the sound components.
Older Sound Blaster cards did not have a software mixer but they had a fixed and balanced sound between the FM (OPL) and the PCM (SB), so the game programmer actually developed the game to sound balanced on the older SB cards.

I have noticed that with my SB-Pro2 clone sound cards and DOSBox the FM music with practically all the old games is much too loud with the default mixer settings where FM equals SB, so I decided to investigate.
I found a thread with a recording of the intro song of GODS using and older SB1.5 by Phil.
This intro song combines the FM and SB sounds so they have to be well balanced for the intro song to sound right, and I assume the SB1.5 has the right balance as the programmer intended.

With the SBPro2 clone card I have I had to set the FM to 5 where the SB is on 8 (all out of 15).
DOSBos mixer FM had to be set to 60 (out of 100) to sound correct and match the SB1.5 recording in terms of balance.

After I have matched the volumes, older games that don't have music/sound balance controls in game sounded balanced without one overpowering the other.
Games like Mortal Kombat 1/2, Prince of Persia 1/2, Gods, Skyroads, Lemmings, where the FM music is way too loud in comparison to the sound effects suddenly sounded just right.

If anyone willing to help me and improve the fine tuning, it would be nice to have a recording of the SB 1.0/1.5/2.0 of various games that combine FM and PCM sounds.
The story intro of Prince of Persia 2 will be perfect for testing.
Last edited by James-F on 2016-8-29 @ 09:44, edited 1 time in total.
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Re: FM and PCM Volume Balance of SB Cards

Postby PhilsComputerLab » 2016-8-29 @ 09:41

Well, the 1.5 and 2.0 do not have a mixer. AFAIK the SB Pro was the first Creative card with a mixer.

This SB Pro stuff does interest me lots, but I just do not have the time currently. Too many projects I'm working on already. Someone send me some free time :dead:
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Re: FM and PCM Volume Balance of SB Cards

Postby James-F » 2016-8-29 @ 09:48

Thanks Phil, when you'll have the time a recording of the story intro of Prince of Persia 2 with a SB 1.0/2.0 will be perfect for testing to get this thread going and find a perfect balance between FM and PCM for newer SB cards.
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Re: FM and PCM Volume Balance of SB Cards

Postby Scali » 2016-8-29 @ 09:56

I've had an SB Pro v2 in my machine for years, and I basically always had the mixer flatout on the FM and DAC channels, and controlled the overall volume with the dial on the back.
The SB Pro's mixer was designed to have the same balance between FM and DAC as the earlier SBs had 'hardwired', so there was never any need to adjust anything.
PC speaker and CD-rom were a different story, since they are somewhat system-dependent. I didn't run the PC speaker flatout, because it was quite loud.
Last edited by Scali on 2016-8-29 @ 09:56, edited 1 time in total.
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Re: FM and PCM Volume Balance of SB Cards

Postby Jo22 » 2016-8-29 @ 09:56

PhilsComputerLab wrote:Well, the 1.5 and 2.0 do not have a mixer. AFAIK the SB Pro was the first Creative card with a mixer.

Yup, I think James-F means the analog mixing circuit, which combines the synth and the DAC audio and passes it to the amplifier.
Don't know for sure, but I think that "mixer" consists of a few caps and resistors. If we find out the right balance,
we can program the real mixer on a SB Pro/16 to the right setting for older games.
Nice project! :)

Edit: Quote added. Why are you people always so fast ? :cry:
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Re: FM and PCM Volume Balance of SB Cards

Postby James-F » 2016-8-29 @ 10:00

Jo22 wrote:Yup, I think James-F means the analog mixing circuit, which combines the synth and the DAC audio and passes it to the amplifier.
Don't know for sure, but I think that "mixer" consists of a few caps and resistors.
If we find out the right balance, we can program the real mixer on a SB Pro/16 to the right setting for older games.

Precisely!
And there are tons of older games that rely on the fixed balance of the older SB cards.

Each sound card is different, so we need to find an easy way to balance the FM and PCM sounds with these new cards including dosbox.
The most precise way would be to play a sine from the FM and then from the PCM through an old SB card, and take the peak readings of both.
Then do the same with the new SB card and tweak the mixer to have the same peak ratios.
But a simple recording of PoP2 intro would suffice to adjust by ear.
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Re: FM and PCM Volume Balance of SB Cards

Postby James-F » 2016-8-29 @ 10:51

Okay here is the perfect way to record the old SB balance:

All you have to do is hit the record button on your new PC and play the opl440.com for a couple of seconds on your old PC with the SB 1/2 card.
Then play the 440_0db.WAV for a couple of second (command: MPXPLAY.EXE 440_0db.wav) on your old PC.
Now we have a true FM to PCM volume ratio recording from an old SB card.

If anyone willing to help, I would greatly appreciate it.
Attachments
SB2TEST.zip
OPL440.com
MPXPLAY.EXE
440_0db.wav
(764.6 KiB) Downloaded 22 times
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Re: FM and PCM Volume Balance of SB Cards

Postby Jepael » 2016-8-29 @ 17:25

Nice.

Just in case anyone is wondering, the OPL440 sets the channel to additive synthesis mode, so the sine wave amplitude is actually sum of two operators running at full volume.

As some SB cards have also the CMS chips, for completeness sake, it would be nice to test the mixing level of CMS audio too.
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Re: FM and PCM Volume Balance of SB Cards

Postby James-F » 2016-8-29 @ 17:46

Yep, Adlib Tracker confirms.
I can generate the exact same signal using the AM connection with sinewave on each operator at full volume.
OPL440 AT2.png


But I still need the SB2 recordings to accomplish something for the good of all dos gamers. :cool:
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Re: FM and PCM Volume Balance of SB Cards

Postby Jepael » 2016-8-29 @ 21:33

I wrote a tool to get 440 Hz tone from the CMS chips. Should work with SB 1.x and SB 2 cards with CMS chips installed. I haven't tried it with my SB 1.x yet, but it emits a tone under DosBox (although about 490 Hz because DosBox CMS emulation is a bit off with the chip clocks).

If you want I can post it here too, but the topic was strictly about FM and PCM volume balance, not CMS :)
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Re: FM and PCM Volume Balance of SB Cards

Postby James-F » 2016-8-30 @ 04:05

Please go ahead, we are doing science here not playing games.
Hope someday someone will be generous enough to participate in this experiment and provide a recording of his SB. :happy:
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Re: FM and PCM Volume Balance of SB Cards

Postby Jepael » 2016-8-30 @ 19:25

Well, here it is. Feedback appreciated, if anyone has a Gameblaster or SB with CMS chips at hand.

Again, currently works only for CMS chips at 220H, but should work on SB 1, SB 2 and GameBlaster as they are all identical regarding the SAA1099P chips. Rumors say accessing cards with logic to lengthen CMS write cycles without CMS chips actually present may hang the system.
Attachments
cms440.zip
Tool to get a 440Hz tone out of CMS/GameBlaster compatible sound cards.
(824 Bytes) Downloaded 24 times
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Re: FM and PCM Volume Balance of SB Cards

Postby Jo22 » 2016-9-17 @ 14:27

Hello, everone. I've done some recordings for you.
I have used sound cards from my own little collection. They all work, but are also quite old.
Perhaps some caps need to to replaced to restore former sound quality.
Attachments
aztech.jpg
Aztech V2.3A
aztech.ogg
(258.01 KiB) Downloaded 17 times
ct1350b_rev4_recap.jpg
Creative SB 2.0, CT1350B REV 4 (recapped)
ct1350b_rev4_recap.ogg
(260.48 KiB) Downloaded 18 times
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Re: FM and PCM Volume Balance of SB Cards

Postby Jo22 » 2016-9-17 @ 14:33

A few more..
Attachments
soundmachine.jpg
QuickShot SoundMachine, SB 2.0 clone card, DSP 2.02/CT1336A, 1992
soundmachine.ogg
(282.39 KiB) Downloaded 17 times
sbclone.jpg
Unknown Sound Blaster clone, SC801 FM, FCC ID: J4UAV202P3
sbclone.ogg
(293.59 KiB) Downloaded 11 times
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Re: FM and PCM Volume Balance of SB Cards

Postby James-F » 2016-9-17 @ 15:04

Finally! This is great, thank you Jo22!

Question,
Is it the recordings of the following?:
OPL440.com
MPXPLAY.EXE + 440_0db.wav

What is first, what is second?
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Re: FM and PCM Volume Balance of SB Cards

Postby Jo22 » 2016-9-17 @ 15:10

Hi, there! Glad I could help! :)

Yes, FM first, then the wave sample.

Btw, I've a few more cards to test..
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Re: FM and PCM Volume Balance of SB Cards

Postby James-F » 2016-9-17 @ 15:13

Few more cards? This would be great!
The Aztech and the Clone have some serious distortion in the WAV sample, but the Creative and QuickShot are clean.

I am going to produce DOSBox FM to SB level matching ASAP.

EDIT:
There is exactly 8.5db difference between FM and WAV on both Creative and QuickShot cards.
To recreate that in dosbox with Nuked-OPL, FM should be set to 75, not 100.
The following command should recreate a perfect balance between FM and PCM in DOSBox with Nuked-OPL patch.
Code: Select all
mixer fm 75



@Jo22
Can you please also make a recording of the CMS along with OPL and WAV with the CT1350, attached by Jepael before your post.

Also, can you please record the intro song from the game GODS with the CT1350 card?
This should give another perspective of balance with actual content, since the SB2.0 also filters the OPL to some degree.
It is around 2:30 minutes long.
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Re: FM and PCM Volume Balance of SB Cards

Postby Jo22 » 2016-9-17 @ 16:18

James-F wrote:@Jo22
Can you please also make a recording of the CMS along with OPL and WAV with the CT1350, attached by Jepael before your post.

Also, can you please record the intro song from the game GODS with the CT1350 card?
This should give another perspective of balance with actual content, since the SB2.0 also filters the OPL to some degree.
It is around 2:30 minutes long.


I would love to do this, perhaps in the next three days. I have to make sure I get my GAL chip correctly programmed.
The Philips SAA1099 chips are already here. :-)
Is a REV 4 card fine for the CMS upgrade ?
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Re: FM and PCM Volume Balance of SB Cards

Postby Jo22 » 2016-9-17 @ 16:24

And once more..
Attachments
protak.jpg
Protac ThunderBoard clone
http://www.amoretro.de/2011/06/protac-thunderboard-clone-opl2.html
protac_conv.ogg
(430.91 KiB) Downloaded 11 times
Protak.ogg
FM and sample (tbtest)
(361.33 KiB) Downloaded 13 times
ct1350b_new.jpg
Creative SB 2.0, "SOUND BLASTER CT1350B", DSP v2.02, CT1336A
ct1350b_new.ogg
(288.58 KiB) Downloaded 22 times
Last edited by Jo22 on 2016-9-18 @ 15:28, edited 1 time in total.
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Re: FM and PCM Volume Balance of SB Cards

Postby James-F » 2016-9-17 @ 16:35

Excellent!

The SB 2.0_new has exactly 8.5db difference like the previous you posted, and they both sound and measure very clear.
The QuickShot SoundMachine looks like an exact replica of the Creative and sound like one, great card.

Do you have a SB 1.0?
Can you please do one recording with CMS too with the CT1350B?
EDIT: Sorry I misunderstood your previous post, Yes the REV4 will be fine, hope the programming will go easy.
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