Bluetooth Audio Adapter Hacked to Switch Off Amplified Speakers

bluetooth-audio-amp-auto-switch

This Bluetooth Audio Adapter is meant to connect a Bluetooth audio source (like a smartphone or tablet) to a speaker system with a plain old line-in connection. It has the ability to automatically connection when the Bluetooth device comes into range. Sounds convenient until [Andreas Pösch] points out that he still has to switch the speakers on and off manually. This hack automates the entire thing using a bit of additional hardware.

If you look closely you’ll see that the black cables have barrel jacks. This is a power pass-through rig that he whipped up. The protoboard includes a 7805 linear regulator which feeds power to the green circuit board in lieu of it’s original power adapter. A MOSFET switches outbound power headed for the speakers. All of it fits inside of the original enclosure, and he only had to add one port for the AC adapter.

This would be absolutely perfect for an antique radio retrofit. One of these adapters can be had for just over thirty bucks!

17 thoughts on “Bluetooth Audio Adapter Hacked to Switch Off Amplified Speakers

          1. It pairs as “DMZ-Music”, which by googling reveals that the “offcial” Modelnumber is “DMZmusic MZ-301″ – I couldn’t find anything out about the Chipset however.

  1. Or just build an audio activated switch. when audio is present close relay, ~30 seconds after audio goes away open relay. pretty darn easy with analog only components, even easier with a picaxe. And then it would work with any device.

    1. Thats a bit more complicated that a single transistor as the guy has used. The BT device has an LED ‘connected’ light so linking that makes more sense (binary on/off when you want the amp on/off). I think that if you had to take the time to physically plug in your device to the aux, the power button ~1m away from it isn’t worth the effort of automating.. i would imagine that most wireless audio devices have a status led of sorts (certainly ‘connected’ is require to know your device is connected anyway!)

    1. That’s actually a valid question to ask as there is what appears to be a
      regulator (U3) on the module itself. The input voltage would be limited
      to the lowest of 10V rated bulk capacitor, regulator and/if any other
      circuits uses make use of the input voltage directly.

  2. I got this dmzmusic wz301 usb bluetooth reciever and it works like crap with windows 8. It has connection problems and will distort sound after some time.

  3. Just wondering if your solution was for a single speaker or a pair. I have been looking for a solution which I could hook up to two identical active speakers which could be paired with BT as a single stereo Left right. Most of the solutions have a single L/R mini-jack so that I would have to run a wire across the room to the second speaker. This is obviously not good. The best sounding active speakers have seperate inputs. I am wondering if there is something out there to connect and still retain sync and stereo?

  4. Hi Mic and others, I have ordered this receiver thinking I will use it in my car for streaming phone call audio to car speakers and use the phone microphone just like i do with aux cable. but have found out that when Bluetooth is on, the phone microphone will be switched off. Have tried to read settings in soundabout android app (https://play.google.com/store/apps/details?id=com.woodslink.android.wiredheadphoneroutingfix&hl=en) whether it contains any setting so i can enable phone microphone with the receiver. Can anybody help me with this? Will be highly appreciated. Thanks in advance.

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