I previously posted details about how I modified my squeezebox 3 in the "Best Mod?" thread but rather than hijack or get lost in that thread I think it better to move this over to its own thread. I'll repeat my earlier description of the mods and then add some pictures to give a better feel for how this is done. First my previous post on the modification:
Over the holidays my brother-in-law and I bought several squeezebox 3s and went about modifying them in a some what systematic fashion. We would make changes to a unit and when that sounded better than the stock unit then that become the reference and we evaluated future changes against the best sounding one. The version that we settled on as sounding best was as follows: 1)Power supply upgrade - just replace the stock wall wart with a surplus regulated 5v supply. The one we used was surplus from some SGI equipment and was rated at 1A. Opening it up showed it to have a hefty transformer and a nicely regulated output. 2)Digital output upgrade. We replaced the stock output RCA with a 75 ohm BNC connector. The one we used was made by Amp and sourced from Digikey - their part number A24598-ND. We also changed the wiring to the output jack. If you trace the wiring, you see that there are 2 inductors in the output path, L8 and L9. We removed these and took the digital output directly from the resistor voltage divider further upstream. I don't have the unit in front of me but I believe the resistor numbers are R55 and R56 - 107 ohms and 245ohms. We also added a transformer output using Scientific Conversions SC916-01 1:1 shielded digital transformers. 3)DAC upgrade - We changed the stock PCM1748 to a PCM1748KE and found the higher grade DAC chip to be a significant improvement. 4)Analog ouput - We removed the output op amp entirely and removed associated output caps from this op amp and from the PCM1748. The signal was taken directly from the PCM1748KE chip. Blackgate 4.7uf N 50v capacitors were used for the output. These were mounted directly at the RCA output jacks and then wires were run back to the DAC output. It was important to remove the unused op amp. I'm not sure if the reduced power draw of the op amp helped the DAC power or if the op amp was picking up noise and amplifying it but things sounded cleaner with the op amp gone. Another change we evaluated but did not like was replacing the power supply caps on the DAC chip with Black Gate 47uf 16v Std caps. We found the sound degraded compared to the stock surface mount caps and switched them back in. When we started we found the best sound came from the Toslink output going to a Monarchy DIP dejitter box to a highly tweaked ART DIO. Preamp was a Manley tube preamp and the power amps were either homebrew 211 amps, homebrew UCD400 amps, or Nuforce Ref 8s. The SPDIF out was the next best sound and the analog output was a distant 3rd. At the finish the best sound came from the analog outputs with the SPDIF a small but noticeable distance behind followed by the TOSLINK even further back. Now here are more details on what this looks like inside the squeezebox. The picture IMG_0258 shows the squeezebox with the front panel removed. The panel is held in place by 2 torx T10 screws accessible from the back. The picture IMG_0262 shows the torx screws that hold the circuit board to the cabinet. The picture IMG_0265 shows the connection to the digital output BNC which is installed on the back panel. I used a shielded transformer, so the red wire goes to the BNC +, the white wire goes the BNC - and the black wire is the shield and goes to the circuit board ground connection. The transformer can be seen in the far right of the picture tucked below the analog output right RCA jack. The picture IMG_0267 shows the squeezebox with the wireless card removed which is helpful when doing the modification. To remove the wireless card one disconnects the antenna from the card, releases the clamps on the side of the card, angles it up and then pulls it out. The bottom card is held in place with sticky tape towards the front and via a snap in connector in the back. To remove it one lifts the back so the connectors disengage and then gently pulls on the front to remove the card from the sticky tape. The picture IMG_272a shows details of the analog output. I removed the output op amp, replaced the PCM1748 dac with a higher grade and ran the analog output through Blackgate caps directly from the PCM1748KE. These caps are mounted right at the RCA output jacks and are the red capacitors shown in the pictures. Wires are run back from the caps to the pads connecting to the DAC output as seen in the next shot. The hardest part of the entire modification is removing the PCM1748 without destroying the circuit board traces. Its really easy to do this if you don't have the right equipment so be careful. I actually did mess up one trace when I removed the PCM1748 shown in this picture and had to solder a tiny wire to the chip pins instead. It takes a steady hand to do this without shorting out pins. Hope this is helpful to folks. ---Gary +-------------------------------------------------------------------+ |Filename: IMG_0272a.jpg | |Download: http://forums.slimdevices.com/attachment.php?attachmentid=640| +-------------------------------------------------------------------+ -- GaryB ------------------------------------------------------------------------ GaryB's Profile: http://forums.slimdevices.com/member.php?userid=3169 View this thread: http://forums.slimdevices.com/showthread.php?t=19822 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
