A conceptual diagram of the fifth prototype is pictured below.

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The new design has been broken into two boards. They are the Audio board and the Control board. The Audio board contains the Power Supply and the Amplifier. The Control board contains the Communications and the Central Processing. The idea here is to break the dependence between Audio and Control. By separating the two functions, Audio and Control boards can be developed independently from one another. With a little bit of forethought, it should be possible to develop an interface between the two that can support several generations of boards.

This should open up a large set of options for DigiSpeaker. For instance, Prototype V will have an MPC5200B based Control board that uses powerline modems for its communications. This board will work well in certain installations (ones with newer powerline wiring) and could be mated with several different Audio boards that deliver different degrees of performance. However, in the cases where powerline modems are not workable (large apartment buildings, old wiring, ..etc), then another Control board based on wireless technology might be used. That board would still have the same set of Audio boards available to allow the delivery of different levels of audio performance (more power, better THD, ...etc). In the future, installations might use a mixture of Control and Audio boards to solve various communication problems and deliver different levels of audio performance.

Note that Prototype V can still be used as a mono-channel amplifier. The same goals of Prototype IV are still in force for this design. That is, a pair of Prototype V DigiSpeakers should be able to play Left and Right stereo signals in a single zone and that each DigiSpeaker will bi-amp or tri-amp its speakers.

Prototype V is the first implementation of this new design concept. It will contain a Control board based on the MPC5200B and use powerline modems from Intellon and Insteon for its communications. The Audio board will have a 65W audio power supply and Class D amplifier. The details follow:

1. Audio Board
1. Logic Supply. A logic supply will be added to the Audio board to power the Control board (and any logic on the Audio board). We are targeting a 15W power supply that delivers 1A at 15V. The design will be something simple. Something along the lines of a Flyback converter based on the NCP1055.
2. Audio Supply. The Audio board will contain an Audio quality power supply. Size and Heat are important to DigiSpeaker so a switch mode power supply design is purposed. This design will targe 65W of audio power. The power supply will conform to energy savings, power factor and EMI regulations. Something along the lines of a Flyback converter based on the UCC28600 is being considered.
3. Amplifier. The Audio board will contain a Class D power amplifier in the 65W range. We are considering the TAS5706 because it is a closed-loop architecture with improved THD performance. This chip is a little underpowered for DigiSpeaker (on 40W for tweeter and woofer). So, we might also include the TAS5601 as a subwoofer driver. This chip also uses a closed loop architecture for improved THD performance.
2. Control Board

The Control board is pretty much the same as the previous prototype. One thing to notice is that AC power is actually being routed to the Control board. Jon and I have discussed this at length and finally concluded that we want all the communication and central processing on the Control board. One big concern is safety. It is not typical that AC power is actually routed to a logic board. Typically, power for a logic board is produce separately and sent to the logic board. This is the case with Digispeaker. However, since the Prototype V Control board uses powerline modems, then the AC must be routed to the Control board for decode/encode. This will make a certain area of the Control board 'hot' and will have to be specially marked and shielded so novices can still work with the board.

This alternative was to place the Intellon and Insteon chips on the Audio board and only ship over the MII and Serial signals. However, in the end, we decided this would 're-couple' the communications with the Audio sections and defeat the purpose of the new two board design. In addition, future wireless based Control board will not require Intellon and Insteon so Audio boards developed with those components will be have unused sections. This just didn't make sense so we moved the powerline communications to the Control board. We just agreed that the AC signal will have to be isolated, shielded and well marked so nobody gets hurt.