Hello, read in the manual that you can disable the internal amp of the Sound Blaster Pro, but it doesn't say how (Pg. C-2 does not say anything about this), anyone done this or knows what jumper i must remove or install so that can be done ?
Want to try to record without the internal amp to get the most possible clean audio signal, the card is a Sound Blaster Pro CT1330A rev4, thanks!
Can you take a picture of the top right hand corner of the board, showing the markings on the IC (looks like it starts with TDA, if it is then it's the output amplifier) and the legend on the PCB near the header close to the 3.5mm jacks.
My money is on that header (or part of it) acting as an line out connector which allows you to get the signal before it reaches the volume control and then the amplifier.
Found a better pic on the net , yes this might be the case as you say but maybe not cause in the diagram i can't understand if the speaker out LR is amped or not , it seems that there isn't an easy jumper way to be open/closed so you can get no amp from the speaker output or it's undocumented , i'll see if i can make a cable or record from the normal output with a little bit of noise...
The TEA2025 is the output amplifier.
The TDA7324 is possibly an amplifier for the mic input and/or an automatic level control.
The electronic engineer in me would probably try probing around with a crystal earpiece (using the tip of the 3.5mm plug as a probe, no need for a ground), set the card to output a constant tone and then trace backwards through the circuit looking for a place where I could pickup audio which is unaffected by the rear panel volume control. I'd then solder screened cable to the board and feed the signal into a suitable buffer amp to give a low-ish impedance line level output.
(The computer engineer in me would look for a card which had a straight line out socket on the back...)
psy_ wrote on 2021-01-05, 10:55:Found a better pic on the net , yes this might be the case as you say but maybe not cause in the diagram i can't understand if the speaker out LR is amped or not , it seems that there isn't an easy jumper way to be open/closed so you can get no amp from the speaker output or it's undocumented , i'll see if i can make a cable or record from the normal output with a little bit of noise...
I can read in the documentation that speaker out LR is amped, because it says "3V at 4 ohms". Without amplification, typical line level is specified as "0.7V at 10kOhm". I guess Creative Labs planned to add the jumpers to bypass the speaker amp, but ditched the jumpers (possibly due to PCB space constraints) and forgot to update the manual.
Thanks @mdog69 and @mkarcher, i will not modify the card cause it's a nice sbpro and i'd like to keep it that way 😀
