TDK Cast Speakers

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As it turns out, the TDK v513 Sound Cube is Google Cast compatible! Well, if you buy a Chromecast. And an audio extractor. And if you've got a soldering iron it certainly helps...

I had purchased a TDK Sound Cube a while ago with the intention of using it as a Bluetooth speaker. The problem with Bluetooth (in addition to the pairing and security issues) is that my phone needs to be close to the speaker. Sure, I'm not literally tethered by a cable, but if I head into another room the sound breaks up, disconnects, and bad things happen. To make matters worse, if I'm listening to music my alerts will be shunted to the speaker, and opening up a game or another sound-related app really kills the mood. Enter Google Cast - initially for video but now available in a series of speakers. That cost an arm and a leg. And replace a speaker I've already got. Then it hit me, the TDK has a USB charger built into it so I could run the Chromecast off that port. Then I just need an HDMI audio extractor to route the audio into the 3.5mm jack in the back. I could tape these to the back of the device, but that's ugly and messy. And I've got a soldering iron...

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This may change the audio quality of your speaker, it's very well padded inside so if you're an audiophile this may change the audio profile of the speaker. I didn't notice anything, but I'm old...

This will certainly void the warranty on your speaker, and may have an adverse impact on your Chromecast and audio extractor warranties.

Of course, if something bursts into flames don't blame me!


  • Of course, I already had the speakers. I have no reason to believe that other Bluetooth speakers, especially those that run off 5V or have a USB power jack, won't work with this setup.
  • You'll also need a Chromecast - available anywhere.
  • You'll also need an HDMI Audio Extractor. The one linked is nice because it's passive, but you'll need to modify it (see below).
  • 3.5mm stereo audio cable pigtail - perhaps from one of the many 3.5mm to RCA adapters I seem to collect.
  • Either a second 3.5mm connector or a right angle adapter.


First you'll want to remove the bottom of the speaker (unplug it first, of course). There are three exposed hex screws, and an additional four under the rubber pads in the corners. These latter ones are a bit of a tight fit, so if you're using standard bits you may need to find a narrow holder for them. Be careful, there is a gasket seated in the base of the speaker which may come out. Mine did and ripped, so I just discarded it.

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Remove the circuit board on the bottom of the speaker. There are a handful of black hex screws, and a small black plastic cover (with a lot of adhesive on it), but this was pretty straightforward. Be careful about dropping screws, they'll stick the the magnets in the speakers and be hard to find. On the bottom of the board there is some black foam you'll need to lift to access the connector solder joints.

Solder the USB cable to the USB header as shown below to the left, you only need the power leads connected, the middle data leads can be removed if you've got a full USB cable. It doesn't hurt to check this connection against the Chromecast to make sure things aren't reversed.

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Solder the three leads from the 3.5mm cable to the audio connector as shown above to the right. The ground gets connected close to the edge, right speaker on the right and left speaker on the left. Note that there's a physical connection that needs to be made in the connector to make this work, unfortunately I didn't notice this until after I had reassembled things so I just left it as-is, you can try playing with the other pins to see if that helps.

I used some black electrical tape to keep the cables in place and then replaced the black foam.

You'll need to modify the VGA adapter to pretend it's actually connected to a monitor. I did this by pulling off the VGA connector (it just pulls off with pliers) and adding a drop of solder between pins 1 and 6 (connecting "red" to "ground"). This is the bit I'm not very happy with - I should have used a resistor, but I'm counting on the idea that the Chromecast would be current-limited and, if not, the USB definitely is limited to 2.1A and the worst I should do is blow out the Chromecast. My speaker is also off most of the time so I'm not overly worried.

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Finally, you're ready for a test fit. Plug the Chromecast into the HDMI converter, the 1/8" pigtail into the audio out, and the USB pigtail into the Chromecast. It should be off with the speaker off and turn on when you turn the speaker on. Set up the Chromecast and try casting something to it to see if you can hear the audio.

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For reassembly you'll need to push a bit harder to get the circuit board in place with the extra wires off it. Once it's been screwed back I used Velcro tape on the bottom of the speaker to fix the Chromecast assembly in place. It doesn't rattle and the only thing I need to do is make sure the right angle adapter is in place for the Chromecast to work. Everything else works exactly as it did before, the USB port just doesn't have as much juice available but the 3.5mm jack still works the same.

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