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SB 2.0, CT1336A, and CMS upgrade

I remember reading about an attempt to reverse-engineer the PAL (the 2 CMS chips were apparently easy to get, but the custom PAL chip was not), so I'm guessing that effort was a success and this is the result?
 
My mistake, that was exactly the article I remember reading, and indeed it says that CT1366A is a problem. I should take a look at my inventory of Sound Blasters and see what versions of CT1366 they have. If I have any CT1366A models I might take a chance on this myself.

edit: as it happens my notes indicate I have two CT1350B Sound Blaster 2.0's, one with a v2.01 DSP and the other with a v2.02. I assume the v2.02 will be paired with a CT1366A but I haven't looked at the physical cards yet.
 
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Xacalite said:
It was considered impossible.
But now there's this - https://www.ebay.com/itm/Improved-C...-CT1350B-compatible-with-CT1336A/283307302605
Can anybody confirm that it actually works?
Click to expand...

I can't say anything about this particular seller's offerings. However I can tell you for certain that original Creative chips exist that are compatible with the CT-1336A. I bought a CT-1350B w/CT-1336A chip from someone on eBay last year, that had an authentic set of C/MS chips installed. I asked the seller to test the Game Blaster mode with Test Drive III, which he did. Said it worked fine. So I snapped up the card. When it arrived, I installed it in my Amstrad Mega PC, and... sure enough, Game Blaster music works 100%. Surprised the heck out of me.
 
DeathAdderSF said:
I can't say anything about this particular seller's offerings. However I can tell you for certain that original Creative chips exist that are compatible with the CT-1336A. I bought a CT-1350B w/CT-1336A chip from someone on eBay last year, that had an authentic set of C/MS chips installed. I asked the seller to test the Game Blaster mode with Test Drive III, which he did. Said it worked fine. So I snapped up the card. When it arrived, I installed it in my Amstrad Mega PC, and... sure enough, Game Blaster music works 100%. Surprised the heck out of me.
Click to expand...
If the other features - especially FM - work as well, there's probably one explanation: there were two variants of the Creative upgrade, or - more precisely - two variants of the PAL chip.
One of the variants has been reverse-engineered by Chuck(G).
That guy from Slovakia has either reverse-engineered the other variant, or recreated its functionality independently.
 
Xacalite said:
If the other features - especially FM - work as well, there's probably one explanation: there were two variants of the Creative upgrade, or - more precisely - two variants of the PAL chip.
One of the variants has been reverse-engineered by Chuck(G).
That guy from Slovakia has either reverse-engineered the other variant, or recreated its functionality independently.
Click to expand...

Yes, Ad Lib + DAC work fine on my card too. Part of the reason I bought it was in case someone wanted to have a crack @ reverse-engineering it. But Chuck(G) wasn't available for it, neither was anyone else I contacted. If this Slovakian guy managed to reverse-engineer it, that's great. Another sound card "mystery" solved.
 
Xacalite said:
If the other features - especially FM - work as well, there's probably one explanation: there were two variants of the Creative upgrade, or - more precisely - two variants of the PAL chip.
One of the variants has been reverse-engineered by Chuck(G).
That guy from Slovakia has either reverse-engineered the other variant, or recreated its functionality independently.
Click to expand...

Hi, I am that guy from Slovakia :)

Yes, I've recreated the functionality from scratch.
Also, there is a very simple fix to make the SB 2.0 compatible with systems without the −5V power line.
Can you spot it?
_ND39016ex2.jpg
There are two variants of the fix, one is destructive and the second is non-destructive. This is the non-destructive one.
 
You are using a different OPL3 DIP chip? Because the original is 3812.
 
rado said:
Also, there is a very simple fix to make the SB 2.0 compatible with systems without the −5V power line.
Click to expand...
So, SB 2.0 needs -5V?
That would be one more surprise from that card - I thought -5V was only for stuff like i8080 cards and similar 1970s gear...

BloodyCactus said:
no, creative put those FM1312 stickers on the chips a lot back then for some reason.
Click to expand...
Indeed, there's no special meaning about those Creative stickers.
Philips SAA1099 with "CMS-301" sticker is still normal Philips SAA1099, and Yamaha YM3812 (OPL2, not OPL3 !) with "FM1312" sticker is still normal Yamaha YM3812.
 
Xacalite said:
So, SB 2.0 needs -5V?
That would be one more surprise from that card - I thought -5V was only for stuff like i8080 cards and similar 1970s gear...
Click to expand...

Yes, NMOS technology usually comes to ones mind.
But there are many cards using opamps which require symmetric power supplies. For example, the CT1350B SB2.0, the CT1920 AWE32 Upgrade and the Roland LAPC-I, all of them require −5V.
The SB2.0 may easily be fixed by adding one resistor between the −5V and the −12V line:
View attachment 50516
Of course, it is not an ideal solution, but at least it is not destructive. The opamp doesn't mind if it is powered somewhat assymetrically.
If there is another card requiring −5V present in the system, a different solution should be considered.
 
BloodyCactus said:
your attachment is broken, but you need TWO resistors for a voltage divider network.
Click to expand...

A voltage divider would be fine, but the SB2.0 works equally well if you feed it with −12V instead of −5V.
The simplest fix is to cut the trace from the −5V ISA power line and to connect the negative power supply pins of the opamps directly to −12V.
But I don't like cutting traces and so I've added a 390Ω resistor between the −5V and −12V power lines. Not an ideal solution, but better than cutting. Quite acceptable when the SB2.0 is the only card requiring −5V.
 
rado said:
But I don't like cutting traces and so I've added a 390Ω resistor between the −5V and −12V power lines. Not an ideal solution, but better than cutting. Quite acceptable when the SB2.0 is the only card requiring −5V.
Click to expand...

so your pumping -12V into the entire motherboard's -5V line? A resistor in series will change its voltage based on the current drawn. I dont know what a 390ohm resistor will really be doing for you, but it shouldnt matter much, the -12 and -5v line have so little current available anyway.

mostly I just dont like the idea of passing -12 straight into the -5v line and making it available to the entire system

if the opamp can take -12 it will probably sound better than with -5 anyway!
 
BloodyCactus said:
so your pumping -12V into the entire motherboard's -5V line? A resistor in series will change its voltage based on the current drawn. I dont know what a 390ohm resistor will really be doing for you, but it shouldnt matter much, the -12 and -5v line have so little current available anyway.

mostly I just dont like the idea of passing -12 straight into the -5v line and making it available to the entire system

if the opamp can take -12 it will probably sound better than with -5 anyway!
Click to expand...


I fully agree with you. Fortunately, I know exactly what I am doing. All the 100% correct solutions require cutting traces or at least using a tape to isolate the −5V line and I don't like that. I have already explained my reasoning behind the decision.

If the power supply provides −5V, then there is absolutely no problem, as the additional current between the negative lines would increase only by 18mA. They are regulated anyway.
If the power supply doesn't provide −5V, then the other system components don't utilize the line.
In a scenario when one would put two or more ISA cards requiring −5V into a system without the −5V line, any damage would be very-very unlikely.
 
Is the lack of -5V a common problem?
Anyway, I would rather modify the power supply, not the card.
 
Xacalite said:
Is the lack of -5V a common problem?
Anyway, I would rather modify the power supply, not the card.
Click to expand...

Yes, many ATX power supplies do not provide that voltage.
If you are skilled enough, you may add an 7905 voltage regulator with 2 caps, but for many people tampering with the power supply would be too risky.
 
rado said:
Yes, many ATX power supplies do not provide that voltage.
Click to expand...
Good to know!
While I keep cards like SB 2.0 for machines many years earlier than ATX, I may occasionally test them in some ATX box.
Note to self: if such a card fails to work with ATX, it doesn't necessarily mean it's broken, remember to check the -5V line as well!
 
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