It can handle 150ma which is more than enough for the mute input. The transistor circuit was built with an A1015 PNP transistor because that's what I grabbed out of my parts bin. Finally, I had to add the small red jumper to re-connect the rest of the circuit that was isolated by my cuts. I also drilled a small hole at the Yellow circle so I could attach a wire to the pin 14 trace (I guess I could have soldered right onto the pin, but the wire was coming from the top-side of the board). I made cuts at the Yellow and Orange circles to isolate pin 14. In the above picture, the Purple arrow shows the location of pin 14. I needed to cut the traces to isolate pin 14, and then make sure that the other bits of the circuit still got the required supply voltage after I made my cuts. It is connected to a positive supply voltage on the circuit board. The main amplifier did require some circuit trace modifications, as shown below:Īgain, the mute pin is pin 14 on the TDA1554Q. The hardest part was cramming the jack into the subwoofer case and bringing the voltage and signal lines to the jack and the transistor circuit (which was simply soldered right onto the jack). Getting this thing together was not too difficult but it did require a dremel a razor and some drill bits.
When the plug is connected, 0v will turn the transistor OFF (muting the amp) while 5v will again leave the amp running. When the control plug is disconnected, 5v is supplied through the jack and the PNP transistor is kept ON, providing enough voltage across R2 to keep the amp ON. There are two supply voltages in the circuit - one is a 12 volt supply which is available on the audio input board, and the other is a 5 volt supply which is tapped from a regulator on the main amplifier board.Ī 1/8" control plug is used to signal the amp to be muted or not. The mute input of the TDA1554Q is at pin 14. I built the following PNP transistor circuit so that a 5v signal from the raspberry pi will turn ON the amp, and a 0V signal will turn OFF the amp: A little probing around the two boards uncovered both a 5v and 12v source. There are two boards inside the subwoofer of this system - one board is an audio input board, and the other is the main amplifier board. So do this hack only on a TDA1554Q system!Ī quick look at the TDA1554Q spec showed that Von is >= 8.5v and that Vmute is 3.3 to 6.4v.
The TDA1554Q replaced the OM8384J chips that were in older versions - I can't find a spec on the older chip so I do not know if it has the same mute pin.
#Cambridge soundworks pcworks Pc#
This hack will work on a PC Works speaker system that uses the TDA1554Q amplifier chip.
#Cambridge soundworks pcworks tv#
I have two of these systems - one is connected to my tv and the other is used on a raspberry pi running Volumio and shairport. It's certainly not an audiophile setup but like I said, it was 35 bucks. The PC Works speaker system was originally 35 bucks around 15 years ago, and it still sounds great in my opionion.
0 kommentar(er)
