How can I connect my motherboard's PC speaker output to my PCI sound card's TAD input (if this is even possible). My PC is on the floor, and while playing Keen, I'd like to have the sound come out through my desktop speakers.
Thanks
(Decommissioned:)
I think it's possible, but you'll have to lower the voltage.
Connecting motherboard's PC speaker (+5V) directly to the TAD input can be dangerous because it designed for line level.
Some sound cards have special input for PC speaker.
The voltage is high but not the current. Adding a resistor of the right value should do, no?
Rather two, forming a voltage divider.
Actually, the PC speaker typically is an open collector output. One pin for the speaker is at 5V, and the other one is connected to a transistor, that might allow current to flow to ground. If you hook the 5V pin to the sound card signal pin, you will just get noise. If you hook the 5V pin to the sound card ground pin, that's a short circuit, which in the worst case might burn traces. If you just hook the signal pin to the sound card, there is no power source to provide any current that flows to ground, and nothing will happen.
What you actually should do is to provide a current path between +5V and the signal pin using a resistor (like 32 ohm, you don't need to go as low as an 8 ohm speaker), and then feed the voltage at the signal pin to the sound card. I don't know whether the sound card has a DC decoupling cap at the input, so I'd recommend to connect the PC speaker signal through a capacitor, e.g. a 100nF mulilayer ceramic cap. The amplitude might be too high, and the easiest way to remedy that is to split the 32 ohm "load resistor" into two resistors. I'd suggest to use this circuit: The 5V goes into an 10 ohm resistor, and then the path forks. One end of the fork connects to a 33 ohm resistor that connects to the signal pin on the other end. The other end of the fork connects to a 100nF cap, which goes into the signal input of the sound card. The 10/33 ohm split should provide a usable level, assuming the expected level at the TAD connector is around line level.
It seems like it's not easy task, since this is unusual audio signal.
Solution:
PC Speaker Sound Device. Need advice.
@Darmok did great job. Bravo!
ott wrote on 2026-03-24, 20:27:It seems like it's not easy task, since this is unusual audio signal. […]
It seems like it's not easy task, since this is unusual audio signal.
Solution:
PC Speaker Sound Device. Need advice.@Darmok did great job. Bravo!
Thanks! This is what I was looking for. @SMA also did something like that (here), but this is much simpler and looks a lot easier to assemble.
(Decommissioned:)