Wednesday, July 16, 2014

Wireless Home theater Circuit using Bluetooth Headset

The post discusses a 200 + 200 watt wireless home theater circuit using a class D amplifier and a Bluetooth headset as the wireless module. The idea was requested by Mr. Sudipta Mandal.

The Request

I want to make my home theater wireless. My home theater model is Sony SRS-D9 2.1 channel. I also want the audio to be stereo. Range should me minimum 2 meters. Is it possible through Bluetooth module or RF transmitter & receiver? If so please suggest how to connect these modules to transmit and receive audio signals. If it is possible through Bluetooth then how to connect the Bluetooth module to my home theater? If a small circuit is required I can make it on my own but for that I need the circuit diagram and specifications of components required.

The Design

In one of the previous articles we learned regarding the internal constituents of a Bluetooth headset gadget and in another post we discussed how its speaker pins could be used for activating a relay.

In response to the above request, in this article we investigate how a Bluetooth Headset could be used for making a home theater system circuit.

The idea is simple, it's about finding a suitable differential power amplifier circuit  and integrating the Bluetooth Headset speaker wires with the inputs of the amplifier.

For the proposed application here we have used an example 200 + 200 watt class D power amplifier circuit using the IC TDA8953 from NXP Semiconductors.

The complete schematic of the power amplifier can be witnessed in the below given diagram. It includes two differential inputs meaning the chip supports a stereo class D input.

The output is single ended though and is capable of driving two ground referenced 4 ohm speakers rated at 200+ watts each.

Each of the inputs of the above shown class D amplifier could be directly configured with the cut/stripped speaker wires of a scavenged Bluetooth headset circuit as given below:

Disconnect the speaker wires from the speaker, strips the ends carefully for the recommended integrations with the amplifier inputs

For using both the inputs of the amplifier and for enjoying a stereophonic home theater response, another compatible and appropriately paired Bluetooth headset unit will be required. 

Once the integration of the two Headsets, paired with source Bluetooth is done, a throbbing crystal clear class D 400 watt stereo music could be experienced over the attached speakers.

The system could be positioned as a home theater system or simply for enjoying a pure 400 watts of music from your cell phone or other Bluetooth compatible gadgets.

If you already have a ready made home theater amplifier system, connect the input of the amplifier with any one cut/stripped speaker wire of the Bluetooth headset (if the amplifier is not a differential type) and make sure the negative line of the headset is made common with the amplifier negative line.

Alternatively a bridge network could be employed for rectifying the differential output from the headset speaker and the output could be directly joined with the inputs of the single ended amplifier.

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