While I am happily impressed with the Squeezebox2’s ease of installation and great sound, based on the various threads in this Forum and Tweakers’ Asylum, several mods were undertaken as explained in this post.
[Please note that the CAPS in this post are not “shouting”, but rather, are simply to make the links easy to find.]
First Mod: Substituting a linear power supply (principally because it was cheap and easy).
The supply substituted is a 5 volt 1.5 amp linear supply manufactured for an IBM Lexmark printer and is Model 7202C-3 PN1333561. This is apparently still available for $6.95 from Hosfelt at http://www.hosfelt.com/. To find it type its Hosfelt part number which is 56-534 in the “search phrase” box at the top of the page. This is a fairly impressive linear supply with a measured output is 5.04 volts DC and a 0.9 millivolt ripple!
It has a fairly long outlet cord but the wrong end adapter. Either cut it off and splice on the last few inches of the squeeze box cord or order THIS CONNECTOR which is 2.5 mm by 5.5 mm by 9.5 mm long. Although there are a number of good suppliers on the net, I prefer Mouser as they have a large stock and no minimum order.
When doing this make sure by checking with a meter that the center (inside of the barrel) is the positive (+) terminal. If everything is fine, the meter will read +5.0 or 5.0 volts. If it reads minus, -5.0 volts, something is wrong and you need to reverse the wire connection that was made!
[These indented blue lines in this post denote additional information, details, or explanatory material that are available in its appended MS Word document
…that is in the SBox Mod Detail Word97 doc + Audio Pass Calcs Excel97.zip file attached to this post]
[--Inexpensive multimeters if you need one--]
[--How to do polarity checks on the power supply--]
Results for Linear Supply Mod: I am not sure converting to the linear supply made much, if any, difference. However, the audiophiles in the forum say it does help and it certainty didn’t hurt. In any event, the linear supply mod is so cheap and easy to do that there is no reason not to do it if you are going to fiddle with the insides of the Squeezebox.
Second Mod: Using coupling capacitors to go directly from the DAC chip to the RCA audio outputs.
This has been widely discussed and I wanted to give it a try, particularly if it could be reversed if it didn’t work out. Actually, this mod has also been discussed at length relative to another DAC in the Tweakers’ Asylum and is known as the “SWENSON MOD”! There is also a web page on it HERE.
Basically the idea is to take the left and right voltage outputs directly from the PCM1748 DAC to the RCA output jacks on the back of the Squeezebox. In theory this avoids undesirable changes that might be introduced by downstream components and the output amplifiers, albeit at the expense of a slightly lower output voltage from the Squeezebox.
In looking at the SQUEEZEBOX2 SCHEMATIC which Sean was kind enough to supply in an earlier discussion on this forum, it is clear that he optimum place to pull off the signal would be at the plus (+) side of the coupling capacitors C7 and C39, which are the left and right channels respectively.
[--Comments on capacitor location--]
To do the work the following steps were undertaken:
Step 1: Remove the top of the Squeezebox, but not the board, by loosening the four T-10 Torx screws in the bottom of the Squeezebox2.
[--Where to find a T-10 Torx screwdriver--]
[--Which boards NOT to touch--]
[--Avoiding mounting post locations when installing mods--]
This picture shows that general area of the circuit board and overall modification that was done. Probably more useful is THIS MODIFICATION PHOTO which shows a 560kB high resolution image of the specific Squeezebox modification described in this guide.
Step 2: Locate and remove C7 and C39 which were respectively at the end of the yellow and red arrows in the image below. (Please note that the image below is a low resolution posting image.
For clearer detail please see this MODIFICATION PHOTO which is a 560kB high resolution image of the specific Squeezebox modification described here.
As you can see, C7 and C39 are surface mounted so a bit of care is required.
[--Types of soldering equipment and options for removing SMDs, costs, and personal rating of usabilities--]
[--General issues involved in soldering on printed circuit boards--]
[--Solder choices and recommendations--]
[--Role of, and need for, flux. Flux and solder wick recommendations--]
[--How to solder, things to do and not do including when using inexpensive irons, useful tutorials including NASA training videos, recommendations, etc--]
C7 and C39 are the coupling capacitors between the left and right channels respectively of the DAC and the downstream audio amp to the RCA outlets. (Note: C7 and C39 are the numbering scheme for Squeezebox2; it is probably different for Squeezebox3! These, in any event, come from Pin 7 and Pin 8 which are the bottom two left pins of the PCM1748 DAC.)
As THIS PHOTO OF A REMOVED CAPACITOR indicates, the black plastic base is part of the capacitor.
To continue with Step 2: To unsolder and remove C7 (or C39) do the following:
- Flux the capacitor’s right pad
- Heat the pad with a “wet” iron and tilt the capacitor left
- Flux the capacitor’s left pad
- Heat the pad with a “wet” iron and tilt the capacitor off
- Flux and clean the pads with solder wick
[--Detailed step-by-step directions and guidance--]
Step 3: Cut Traces to RCA Right and Left Output Center Pins
While removing C7 and C39 isolates the output from the DAC, we also need to isolate the RCA output jacks from the analog output amplifier and it’s various parts and filters. Originally the idea was to cut the center connection or to pull up R42/R44 or C44/45. However, the center connection of the RCA plugs is relatively robust and the area around the surface mounts is rather tight. Also, an auxiliary goal was to enable the maximum chance of restoration. A cut trace can be easily restored by cleaning off the ends and adding a drop of solder.
The cut location is shown by the black arrow circles in the earlier MODIFICATION PHOTO. The right trace cut is clearly shown but the left trace is actually underneath the added wire. No special tool is needed to cut the trace, simply an ordinary Stanley utility knife. See the “TOOLS” PHOTO.
[--Detailed step-by-step instructions to cut and monitor trace cut--]
Step 4: Add Wiring for the DAC outputs at the left C7 and C39 pads
The next step is to use the inlet (left) pads at C7 and C39 to wire additional coupling capacitors to the DAC Left and Right Outputs. To do this, two pieces of something like 24 to 30 gauge wire are needed that are 2.5 inches long. You don’t need to go buy anything special as it is likely already laying around: indoor telephone wire, a piece of Category 5 LAN cable, and old serial or parallel computer cable, etc.
[--Importance of “good” wire stripper--]
[--Need for a “third hand” clamp and options--]
[--Detailed step-by-step directions and guidance--]
(See First Reply to This Thread for Step 5, etc. continuation)
Results 1 to 10 of 14
2006-05-06, 11:05 #1
- Join Date
- Feb 2006
Squeezebox Audio and Power Mods: How, Photos, ExperienceDick
Squeezebox2 on wired LAN: Hosfelt linear pwr and DAC audio out mods
Sansui QRX9001 quad: Resoldered and recaped incl BlackGates in audio path
Onkyo T-4711 tuner
Sherwood Newcastle CD-980T
Four Axiom M22ti