Auto-sleep Hacked In PC Speakers

We can commiserate with [HardwareCoder] who would rather not leave his PC speakers on all the time. The Creative T20 set that he uses turn off when you turn the volume knob all the way down until it clicks. So shutting them off means repositioning the volume each time they’re switched on again. This hack kills two birds with one stone by turning on and off automatically without touching that knob.

The system is based around an ATtiny45 and a few other simple components. It uses two ADCs to monitor the rear input channels of the PC speakers. If no sound is detected for more than one minute, the shutdown pin of the speakers’ amp chip is triggered. That’s not quite where the hack ends. We mentioned it monitors the rear input of the speakers, but it doesn’t monitor the front AUX input. An additional push button is used to disable the auto-sleep when using this front input. There is also a fancy PWM-based heartbeat on an LED when the speakers are sleeping.

[HardwareCoder] was worried that we wouldn’t be interested in this since it’s quite similar to a hack we ran a few years ago. We hope you’ll agree it’s worth another look. He also warned us that the demo video was boring. We watched it all anyway and can confirm that there’s not much action there but we embedded it below anyway.

29 thoughts on “Auto-sleep Hacked In PC Speakers

  1. Auto off on a digital amp. How little does this save vs. the added on stuff. My amp is on the timer that wakes me up, so it’s on from wake to zzz. It’s 4.1 class AB. Since I listen to wide dynamic range music and run into low sound YouTubes the sound better not cut out ever.
    Minuses for turning on switching supplies too often vs. keeping them running cool or cold. Or is it still running on those timebomb caps regardless.
    The next thing the greens are going to legal-strate that amps have to work like showers on “thankless” water heaters. Which is how this project seems to work. Throttle down the flow to tub-stall warming trickle and the water goes cold.
    Thankless! Not wrong post.

  2. Hmm. powering a 78L05 from +30v will generate enough heat to not lower the idle power requirements in “deep sleep” i think. using a cheap buck converter solves that problem though.

    1. yeah. The route he took and hack are both interesting but I just opened mine up and soldered a spst switch in place of the clicky one on the pot’s rear. Power strip or in line “lamp switch” on a cord would have worked as well like you say.

    2. Same here, I regularly find old multi switched outlet computer power management units at the thrift stores for around 5$, the ones with a switch for “computer”, “monitor”, “printer”, etc. they usually have some form of protection as well. I have multiple PC’s and peripherals connected to mine, including powered speakers, on several workstations, (I have 4 of them). The simplest power management solution is the best. I wonder if any one still makes these? Mine have RJ11 modem thruputs on the protection circuits which is an indication of how old they must be, although one of them was NOS still in the sealed box, probably donated by a big box store for a tax write off.

      1. Surge proctors still have rj11 passthrough jacks even today, they’re made for your phone line not a modem. Any long wire coming into your house is a big antenna for emf like lightning so it’s a good idea to have a surge protector on your phone line and also cable tv/antenna.

  3. Other approach I used on an older PC: power the 12V speakers directly from the PC 12V power line, from an unused disk drive Molex. One fewer wall-wart, automatic-off, and it even killed the hum from the speakers’ lame-ass power supply.

    1. And you didn’t hang an arduino off the 5V rail – good for you! I will be using this one soon to stick a 12V amp inside the computer case to power external passive speakers, nice solution.

  4. I even do not turn off my pc, so I don’t need to turn off speakers either. Problem solved. Besides that I hate auto-off speakers. Btw. Arduino is missing in this project.

  5. Too bad there aren’t any power measurements. But since I have those same speakers, I thought I would measure the power usage. See how much power being saved.

    I found mine to use 0.08A @ 28V when no sound is going through them. So that’s 2.24 watts.

    (I have no way to measure the quiescent current of the switching power supply, which would be interesting to know.)

    Not sure if I would go to so much trouble just to save 2 Watts. But is a cool hack for sure.

  6. Hi,

    Power measure: 31.7V no sound gives 96.3mA, on sleep mode 49.5mA. I measured this on DC socket, without reopening the case. I wonder how it act without Attiny45 and LM78L05. I’ll check this during next change in soft/hardware, but for now (for me) it does not require any changes.

    It was a fast-hack and main reason was no to set volume every time after switching on, power-save was the second, mostly for serenity ;) . I was a ultra-simple hack, if amp had no sleep mode, I would not bother to do this. I’m pretty sure that whole thing could be done better (maybe only with RLC?) but for the truth I spend more time to write it on my blog, than programming and soldering :)

    If I’d open T20s again, my conscience would tell me to make a pretty PCB with smd, different power source and some fix-ups in C code. Attiny45 type V could be powered from 1.8V and since only low state on amp’s SD pin matters, this circuit could be less power eating. But this is time consuming, and present state satisfies me.

    I have a laptop and when I leave my desk i put it in a sleep from additional button on wireless keyboard, speakers shut down after minute and I’m happy.

    Many years ago when I had a PC, I used similar to Paul’s hack, I connected relay to 5V molex and through it control regular “big” amp on mains.

    I listen to almost any kind of music, sometimes with big dynamic range like classical tunes and speakers won’t fall into sleep even on low dynamics. I admit when I watch something on YT, interviews etc, T20 goes to sleep, but for this (and aux) is additional disable_sleep_mode/enable_sleep_mode push button on the back.

    Thanks for your comments!


  7. How can I hack my T3150 to never ever go into auto-sleep, using them with the tv, but they auto-off / sleep happens too easily. Any chance to solder the board somewhere to stop the auto sleep from happening?

    1. Hey, probably yes. You need to disassemble them and see what kind of amp they have. Then search for datasheet, check if it has something similar to TPA3123, e.g. MUTE/SHUTDOWN pin, check if it’s used, if so you could easily track mute/shutdown circuit and try disable it. If you’re lucky, you could end with soldering additional resistor to pull-up/-down one of amp’s pins only.


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