I was the owner of a pair of Mackie CR3 speakers, until the PCB burnt through, and rather than tossing them out decided it would be worth a try to recycle them.
I bought the following items:
All good so far, except I'd like to reuse the switched volume knob on the Mackie speakers, which has two green LEDs behind it that illuminate when the speakers are turned on.
The switched pot is mounted on a small PCB, with the two LEDs in parallel, and connected in series to the switch. The switch is open when the volume knob is turned off, and closed when turned on.
The amplifier PCB has STBY and GND pads that, when shorted, will put the amp into standby mode:
What I'd like is to have the volume knob switch be able to short these pads when the switch is open. The problem is that these two pads have less than 200 uA, which is the upper limit of the STBY pin on the TDA7498 IC, but I'd like to power the two LEDs that are next to the switch, too.
I have a 5 V and 1 A supply available from the SMPS (the amp is using the 24 V 4 A output) - is there a way with transistors that I could short the STBY and GND when the switch is open, and then when the switch is closed, "unshort" (I assume there's a word for this) the pads, and power the LEDs?
I don't know much about electronics, but will do my best to answer any questions!
Thanks in advance
I bought the following items:
- 24 V 4 A switching power supply - https://www.aliexpress.com/item/32919514666.html
- 2 x 100 W amplifier based on TDA7498 class D amp - https://www.aliexpress.com/item/32951020545.html
- Two-way crossovers - https://www.aliexpress.com/item/32888808236.html
All good so far, except I'd like to reuse the switched volume knob on the Mackie speakers, which has two green LEDs behind it that illuminate when the speakers are turned on.
The switched pot is mounted on a small PCB, with the two LEDs in parallel, and connected in series to the switch. The switch is open when the volume knob is turned off, and closed when turned on.
The amplifier PCB has STBY and GND pads that, when shorted, will put the amp into standby mode:
What I'd like is to have the volume knob switch be able to short these pads when the switch is open. The problem is that these two pads have less than 200 uA, which is the upper limit of the STBY pin on the TDA7498 IC, but I'd like to power the two LEDs that are next to the switch, too.
I have a 5 V and 1 A supply available from the SMPS (the amp is using the 24 V 4 A output) - is there a way with transistors that I could short the STBY and GND when the switch is open, and then when the switch is closed, "unshort" (I assume there's a word for this) the pads, and power the LEDs?
I don't know much about electronics, but will do my best to answer any questions!
Thanks in advance
Last edited: