Tony Moore
07-08-2008, 09:23
Hi All,
I just thought I'd share my experience integrating the Logitech (Slim Devices) SqueezeBox 3 into my custom built DAC. This project started out as an external DAC to accompany my CDPro2 transport a few years ago. This is what it looks like, lid removed:
http://i296.photobucket.com/albums/mm168/TonyMoore300B/DAC.jpg
http://i296.photobucket.com/albums/mm168/TonyMoore300B/DACOutside.jpg
The DAC board itself is the one by Pedja Rogic (the previous version of his DAC, not AYA DAC). It's a TDA1541A based DAC (I have S2 fitted) with no digital filtering. The output buffer board is the one from my old Hawk Audio MPDAC, discrete solid state. (The Hawk MPDAC used the CS4390 bitstream DAC which although good, I found I liked the sound of the 1541 better)
Soon after I built the CDPro2 and DAC I learned about the SqueezeBox (thanks Neal!:doh:) and realised that there is a lot of potential there for exploiting the hardware to get the best possible sound from it. It's taken a while but I've finally managed to interface the SB3 to the DAC using the best of all the available interfaces, the I2S. This took a bit of work as the format of the I2S from the SB3 is not the same as that required for the TDA1541A chip. So I had to use a programmable logic chip (Xilinx Coolrunner II CPLD - thanks Andrew and Nick for your help with the software!) to do the conversion of the format.
The SB3 can be seen mounted on the left, fed by an ALW super-regulator at the back. The I2S signals are tapped off from the SB3 (bit clock, word clock and data) and taken into the Xilinx CPLD dev board, where they are converted from Left Justified format to true I2S. From there the output I2S signals go through my synchronous reclocking circuit (based around D flip flops - to ensure that the signals have the lowest possible jitter, being synched to the accurate Tent clock just millimetres away) and into the TDA1541A (mounted beneath). The reclocking cct is fed from a Tent XO3 clock. The Tent clock is also fed back through the CPLD board and clocks the SB3 so that all the signals stay in synch.
The case is a custom job, built using metalwork from the online CNC workshop Schaeffer. The legs are wine bottle stoppers! (This was to match my CDPro2 based CD player that I'd built a few weeks earlier, way back in 2005)
Sound-wise it is quite nice! And it has a much greater WAF now! :smoking: I have recently bought the SqueezeBox controller so I don't now need to see the display (which is in fact hidden now!) The controller is a great piece of tech!
The only thing I would like to improve is to disable the VFD display and it's power supply. At the very least it would save a shedload of millamps current draw from my super regulator and reduce interference within the case. I don't suppose anyone has any info on the safest way to do that? I've looked around the pcb but nothing is obvious. I'd like to be able to power the VFD off but be able to get it back working again should I need to check or change internal settings.
I shall be bringing along the DAC/SB3 and my CDPro2 to ChesterFest. Both the SB3 and the CDPro also have s/pdif out so we'll also be able to run them through external DACs to make some comparisons. I'm sure that the DAC side of things could be improved some more but for now I will be listening for a while! :)
Tony.
I just thought I'd share my experience integrating the Logitech (Slim Devices) SqueezeBox 3 into my custom built DAC. This project started out as an external DAC to accompany my CDPro2 transport a few years ago. This is what it looks like, lid removed:
http://i296.photobucket.com/albums/mm168/TonyMoore300B/DAC.jpg
http://i296.photobucket.com/albums/mm168/TonyMoore300B/DACOutside.jpg
The DAC board itself is the one by Pedja Rogic (the previous version of his DAC, not AYA DAC). It's a TDA1541A based DAC (I have S2 fitted) with no digital filtering. The output buffer board is the one from my old Hawk Audio MPDAC, discrete solid state. (The Hawk MPDAC used the CS4390 bitstream DAC which although good, I found I liked the sound of the 1541 better)
Soon after I built the CDPro2 and DAC I learned about the SqueezeBox (thanks Neal!:doh:) and realised that there is a lot of potential there for exploiting the hardware to get the best possible sound from it. It's taken a while but I've finally managed to interface the SB3 to the DAC using the best of all the available interfaces, the I2S. This took a bit of work as the format of the I2S from the SB3 is not the same as that required for the TDA1541A chip. So I had to use a programmable logic chip (Xilinx Coolrunner II CPLD - thanks Andrew and Nick for your help with the software!) to do the conversion of the format.
The SB3 can be seen mounted on the left, fed by an ALW super-regulator at the back. The I2S signals are tapped off from the SB3 (bit clock, word clock and data) and taken into the Xilinx CPLD dev board, where they are converted from Left Justified format to true I2S. From there the output I2S signals go through my synchronous reclocking circuit (based around D flip flops - to ensure that the signals have the lowest possible jitter, being synched to the accurate Tent clock just millimetres away) and into the TDA1541A (mounted beneath). The reclocking cct is fed from a Tent XO3 clock. The Tent clock is also fed back through the CPLD board and clocks the SB3 so that all the signals stay in synch.
The case is a custom job, built using metalwork from the online CNC workshop Schaeffer. The legs are wine bottle stoppers! (This was to match my CDPro2 based CD player that I'd built a few weeks earlier, way back in 2005)
Sound-wise it is quite nice! And it has a much greater WAF now! :smoking: I have recently bought the SqueezeBox controller so I don't now need to see the display (which is in fact hidden now!) The controller is a great piece of tech!
The only thing I would like to improve is to disable the VFD display and it's power supply. At the very least it would save a shedload of millamps current draw from my super regulator and reduce interference within the case. I don't suppose anyone has any info on the safest way to do that? I've looked around the pcb but nothing is obvious. I'd like to be able to power the VFD off but be able to get it back working again should I need to check or change internal settings.
I shall be bringing along the DAC/SB3 and my CDPro2 to ChesterFest. Both the SB3 and the CDPro also have s/pdif out so we'll also be able to run them through external DACs to make some comparisons. I'm sure that the DAC side of things could be improved some more but for now I will be listening for a while! :)
Tony.