I'm a fan of two-three way loudspeakers using DSP based crossovers
Since long time I wanted to improve the quality of my AV 5.1 Dolby receiver, and I wanted to do something more radical than just go through all digital/analog conversions on the receiver to just do another analog/digital/analog on the DSP, let alone using the power amp outputs of a standard AV receiver to do it.
My TV is an old Sony cathode ray tube, but picture quality is still pretty good
So, I bought on eBay a pioneer vsx-c502 receiver and I started DYIing.
First, I removed the power amp section, and I pulled up the "error" signal
Then
- I connected directly to the three I2S outputs of the AK4529 codec, and through a buffer I built a CS8421 interface to feed the digital inputs of three miniDSP (I needed an ASRC to fix formats)
- built a board with 6 pga2311 for volume control and amplification (miniDSP has a rather low output voltage)
- built an MSP430 based interface board to manage the mute, speaker ready, AC on, the 3 SCART status signal, PGA2311 control, VSX-502 IR chip, Sony TV remote control data format (for volume up/down and other commands), auto stand-by management
- used an isolator to connect the MSP430 and miniDSP USB, to avoid ground issues
- used low noise TI ref boards for the 2.5, 3.3, +-5v needed by the various subsystems
- took care of all 5 to 3v conversions where needed
- added an always on AC tranformer and power supply for the MSP430
- moved the original internal VSX DC voltage regulators to an aluminum heath sink on the side of the case (they were getting pretty hot and I don't like hot)
- added a relay controlled transformer for the miniDSP power, as they use more that can be provided by VSX built in 5v
- grounding was pretty complex to figure out
I only used breadboarding, I wasn't sure about the design of the various subsystems and I didn't want to go through multiple pcb iterations. So it's a little messy
The attached pictures show the modified receiver. The 6 stereo jacks on the back are used for the two way 5.1 (for the subwoofer I use one straight and one inverted output, for bridged amplification). The other two jacks are for the mute and power on signal to the amplifier (a 12 channel 4780 based unit that I'm half way building)
I used miniDSPs has I had 3 of them available, but any 3 I2S in, 12 out DSP would work fine
Since long time I wanted to improve the quality of my AV 5.1 Dolby receiver, and I wanted to do something more radical than just go through all digital/analog conversions on the receiver to just do another analog/digital/analog on the DSP, let alone using the power amp outputs of a standard AV receiver to do it.
My TV is an old Sony cathode ray tube, but picture quality is still pretty good
So, I bought on eBay a pioneer vsx-c502 receiver and I started DYIing.
First, I removed the power amp section, and I pulled up the "error" signal
Then
- I connected directly to the three I2S outputs of the AK4529 codec, and through a buffer I built a CS8421 interface to feed the digital inputs of three miniDSP (I needed an ASRC to fix formats)
- built a board with 6 pga2311 for volume control and amplification (miniDSP has a rather low output voltage)
- built an MSP430 based interface board to manage the mute, speaker ready, AC on, the 3 SCART status signal, PGA2311 control, VSX-502 IR chip, Sony TV remote control data format (for volume up/down and other commands), auto stand-by management
- used an isolator to connect the MSP430 and miniDSP USB, to avoid ground issues
- used low noise TI ref boards for the 2.5, 3.3, +-5v needed by the various subsystems
- took care of all 5 to 3v conversions where needed
- added an always on AC tranformer and power supply for the MSP430
- moved the original internal VSX DC voltage regulators to an aluminum heath sink on the side of the case (they were getting pretty hot and I don't like hot)
- added a relay controlled transformer for the miniDSP power, as they use more that can be provided by VSX built in 5v
- grounding was pretty complex to figure out
I only used breadboarding, I wasn't sure about the design of the various subsystems and I didn't want to go through multiple pcb iterations. So it's a little messy
The attached pictures show the modified receiver. The 6 stereo jacks on the back are used for the two way 5.1 (for the subwoofer I use one straight and one inverted output, for bridged amplification). The other two jacks are for the mute and power on signal to the amplifier (a 12 channel 4780 based unit that I'm half way building)
I used miniDSPs has I had 3 of them available, but any 3 I2S in, 12 out DSP would work fine
