Mods to Squeezebox

October 1, 2007

I modified a Squeezebox 2. I have not examined the SB3 board or its schematic. If you have an SB3, you’ll have to ascertain which crystal on the SB3 board is the 11.2896MHz clock. This is the one you want to replace. These mods should be done after you finish building the reclocking board.

1. In order to get this project up and running, I decided to use inexpensive 30awg wrap wire to transmit the signals from the SB to my Dac. This is far from ideal, but the results in my system blow away using my $1,100 CDP as a transport. I plan to replace this shortly with shielded CAT5 using LVDS. Here is what I did as far as cabling. First, make up 4 runs of twisted pair 30awg wire. I created a “pigtail”, with these wires soldered to the SB board and then run directly to the reclocker board inside the dac. No connectors. The wire run should be as short as possible. But it will probably be difficult to keep these under 12-18” depending on the size of your Dac’s chassis and location of reclocking board. I used wrap wire and a drill to twist the pairs. You can get this wire in blue, red and white. Get at least two colors and use one colored wire and one white wire for each twisted pair. Designate the white wire as ground. Cut 20” lengths of this wire. After using a drill to make 4, twisted pairs cut them down to a minimum length without inducing strain between the components. You may want to add strain relief for the SB because these wires solder to the board directly. You can of course develop a connector interface or even add LVDS transmission. Even if you do this, you can cut the wrap wire and solder to the LVDS chip and, hence, you won’t have to desolder your existing work on the SB board.

2. Once you have 4 runs of twisted pair cable, twist all of the grounds together at each end. Tin the ground bundle with solder. On the SB board, now solder the ground bundle to a handy ground reference. I used the negative lead of the big capacitor. The ground bundle at the other end of the cable will fasten to the ground input on the reclocking board, but don’t do this yet. Make sure the positive wire of each cable can reach its reference point on the SB board.

3. You may want to tape a label onto each cable as MCK, BCK, LRCK and SDATA to keep things straight at both ends.

4. Once you remove the 11.2896MHz crystal you will see two solder pads. Now solder the MCK positive wire to the vacant pad that runs to pin 1 of the HC74U04 close by. On the SB2 board, this pad is the one on the right when holding the board with the I/O jacks facing up. It’s the pad with the trace to cap C15 (on the SB2).

5. Now locate the three solder traces that run between the XILINX and SB Dac chip. Note that the SB Dac chip is BB1748. Pins 1, 2 and 3 correspond to BCK, DATA and RLCK, respectively. BCK will be located in the corner of the chip, with DATA and LRCK next to it. Now find the 3 resistors that are located on the traces between the XILINX and BB1748 Dac chip. You will be soldering the positive lead of each of the three remaining twisted pair cables to the ***DAC SIDE*** of the leads of each of these resistors. You will need magnification to accomplish this.

6. Try to provide some strain relief for these delicate cables so that the wires cannot be pulled off (and possibly damage) the solder pads on the SB board. That’s it for the Squeezebox mods.