Excuse me for being a newb and a fool... but why would you want to do this? Is that one of the cards that has a powered out.. i.e. can plug speakers into? Is there no line out?

From what I can tell there is no unamplified line out. Just speaker out, mic in, line in.

http://th99.dyndns.org/i/C-D/50402.htm

This diagram here says no, but does it have any jumpers labled OPSR and OPSL? Those are the Speaker out/line out jumpers on most 16s and 32AWEs.

I'm fairly sure that you are stuck with the amp on a Pro 2.

Yes, in its unmodified form I think there is no way to disable the amp. However, I am pretty certain that if you cut the power pin on that 3-pin transistor you can disabling the amplification of the speaker out. I'm just wondering if anyone had a better way before I gave it a try.

...never mind, that's a voltage regulator. I'll examine the card and compare to the SB16 and see if I can come up with anything. The amplifier must in one of the ICs.

You could just get yourself some era-appropriate crap "multimedia" speakers. Labtec or Koss thingers. 😉

The old Craptec speakers, eh?

I think I'll have to pass on that. It appears that there is likely a way to disable the amp through undocumented jumper "J2". It's actually labelled "AUDIO_PWD" which makes it even more suspicious.

I just find it hard to believe that both SB 2.0 and SB16 can disable the amp, but SB Pro 2.0 cannot.

Anyway, if all fails I have identified the amplifier IC, downloaded the datasheet, and will find a way to properly disable it.

I made an attempt at disabling the amp today, and was *partly* successful. What I did was cut the power pin on the ST TEA2025B amplifier chip on the SB Pro. Unfortunately I no longer seem to be getting any sound, or it's just so quiet I can't hear it. It doesn't seem like a very viable solution to the problem. Has anyone yet performed a successful operation?

You want a line out instead of a speaker out? You'll have to solder - put the card on a scanner (both sides) and maybe I can tell you where.

My card is exactly like this:

Can't read all of the chip numbers. The amplifier is TEA20..?

Better idea - the signal is at the volume potentiometer. You should get something similar to line out at the two yellow circles. You could remove the jumpers for speaker out and solder two wires from them to the yellow points.

Thanks for all your help. I'll try it out and see what happens.

Hmm...I tapped into the two points in yellow that you suggested (and connected them to pins 7 and 8 on the AUDIO_PWD header (removing the jumpers), and I didn't hear anything at all.

Have you ever performed this mod before? Are you certain that the audio signals go directly into the potentiometer? It would seem to me that the potentiometer is more than likely integrated into the amplifier circuit to adjust the gain.

http://www.datasheetcatalog.org/datasheet/SGS … ics/mXuruyy.pdf

This is a PDF of the amplifier chip.

Perhaps by examining the amplifier on/off jumpers on an SB16, we can determine how to build a similar circuit for the SB Pro.

Well I only have this Aztech clone. Uses the same amplifier chip (the noise of this card can be reduced quite a bit by adding a metal shield at the back side). It would be very unusual if the signal did not go directly into the potentiometer.

Have you measured which of the pins go to the output connector? 5 and 6 or 7 and 8?

I had a similar issue with an ISA soundcard based on a Crystal cs4237B Chipset. It only had amplified output. The only thing I could do was finding out where the unamplified lines-out left the chip and how they went to the amplifier, then cut their connection to the amplifier entirely. after that reroute the lines-out to an unused jackplug socket but put a capacitor in these lines. cannot recall the rating of the caps now.

But why don't you use a Yamaha OPL3-Sax card instead, I think it makes a great SBPro-2 replacement.

Which OPL3-SAx card is best? I once had a waveforce PCI card, and the noise was quite terrible.

Anonymous Coward wrote:

Which OPL3-SAx card is best?

Anything Yamaha OPL3SA3 [YMF715/718/719], which is an ISA chipset of course. See my review at the bottom of this topic: The Yamaha OPL YMF718-S chipset

Anonymous Coward wrote:

I once had a waveforce PCI card, and the noise was quite terrible.

That is an YMF724 chipset, why would it be noisy?, it uses a Sigmatel DAC.

prophase_j wrote:

Excuse me for being a newb and a fool... but why would you want to do this? Is that one of the cards that has a powered out.. i.e. can plug speakers into? Is there no line out?

I must confess that I don't understand the principal gist of this topic. Is this the fundamental problem: that nearly all modern desktop multimedia speakers are amplified. And if you plug a pair of them in to the speaker port on a CT1600, this will produce bad quality sound, because the CT1600's speaker output is also amplified.

So, I guess an old pair of "Craptecs" didn't have a built-in amplifier. I wonder if there are any modern desktop speakers available that allow you to switch off their internal amp?