Modifying the Squeezebox 3

GBB · « **on:** 2 Jan 2006, 11:53 pm »

Over the holidays my brother-in-law and I bought a bunch of 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.

---Gary

rotcoddam · « **Reply #1 on:** 4 Jan 2006, 02:13 am »

Thanks Gary, that's valuable info for us "not so electronically inclined", but still like to do mods. Maybe I'll go ahead with a SB3 purchase now. Marty

GBB · « **Reply #2 on:** 7 Jan 2006, 08:27 pm »

There hasn't been a much response to this thread (except for Marty - thanks) but I'd thought I'd add a few pictures in case that would be a help to any one else thinking of digging into their Squeezebox.

First here's a picture with the front panel removed. The panel is held in place by 2 torx T10 screws accessible from the back.

After removing the front panel, one removes the circuit board from the cabinet. Its held in place with 4 torx T10 screws as shown here.

As described above, I removed the digital output RCA and replaced it with a BNC and then added a digital transformer. Connection to the BNC can be seen in the next picture. 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.

To do the wiring of the transformer its helpful to remove the wireless card and the card below it as well. To do this one disconnects the antenna from the card, releases the clamps on the side of the card, angles it up and then pulls it out. Here's a picture of the card after removal.

You can also remove the card below the wireless card and it will make some of the soldering easier.

For the analog stage, 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.

This is a set of mods that require quite a bit of experience to complete successfully so only try this if you're confident in your abilities.

---Gary

randytsuch · « **Reply #3 on:** 7 Jan 2006, 09:20 pm »

Hi Gary
Thanks for the information and the pics.
Not sure why there aren't more responses to this thread

.

Right now, I am using my sb3 as a digital transport to feed to my audiosector nos dac.

I just got it from RWA before Christmas with his basic analog mods.

I have been thinking about making mods to the digital output section of my sb3, and was wondering what difference the digital transformer made?

My initial thought was to take a coax cable, and just solder it inside the SB3. The cable has a BNC connector on the other end, to connect to my DAC.

I also found it interesting you replaced some SM caps with Blackgates, and liked the SM's better. Wondering how long you let the BG's break in? In my experience, they sound better after at least 40 hours, but I would give them a couple hundred hours to really let them run in.

Randy

GBB · « **Reply #4 on:** 7 Jan 2006, 11:19 pm »

Quote from: randytsuch

Hi Gary

I have been thinking about making mods to the digital output section of my sb3, and was wondering what difference the digital transformer made?

My initial thought was to take a coax cable, and just solder it inside the SB3. The cab ...

Randy,
The first mod I made was to install the digital transformer but without removing the output inductors L8 and L9. This was an improvement but still wasn't better than the TOSLINK. Next I removed L8 and L9 and connected the transformer right at the resistor voltage divider as shown in the pictures. Originally I had the transformer mounted close to where the original output jack was located. This combination of an output transformer and getting rid of the output inductors was the real deal. I didn't do the complete experiment and see how it sounded without the inductors and without a transformer so I can't comment on that combination.
If you want to wire in a cable directly I'd suggest you get rid of those inductors and wire into the place where my transformer is wired. The bare wire you see in the picture going over the white wires which connect to the output blackgates is connected to ground. Theres a convenient through board hole you can use. The voltage resistor divider where one would connect the other side of the coax is just at the lower left corner of the transformer right behind the white wires. Its the junction of the two resistors I mentioned in my first post. Or if that seems a bit too tough you could solder to the pads opened up when you remove L8 and L9.

Regarding the blackgates for the power supply - I only left those in for perhaps an hour. The sound was so much worse than the SMD caps that I didn't have the patience to let them burn in. Plus I was thinking that the Squeezebox has a lot of RF flying around and the longer leads of the blackgate caps might not be a good thing in terms of picked up RF. So my impatience and pseudo theories convinced me to take them out since the stock caps sounded really good.

---Gary

EchiDna · « **Reply #5 on:** 7 Jan 2006, 11:52 pm »

great list of mods GBB!

I'm going to link it over into the squeezebox FAQ in the square circle

we need more DIY on this site keep it up!

EchiDna

Folsom · « **Reply #6 on:** 8 Feb 2007, 06:09 am »

How hard was the DAC to replace?

Why 4.7uf on the output, would 10uf not be more appropriet? Does removing the OPAMP remove the ability for volume control? What OPAMP is it? (perhaps something better could be put in, if volume control is needed and an OPAMP to make it possible?)

What about panasonics for the power? They are low ESR capacitors.

Are schematics avalible for the SqueezeBox3?

JoshK · « **Reply #7 on:** 8 Feb 2007, 06:35 am »

Great job Gary!

A great thread. I really like your controlled approach.

GBB · « **Reply #8 on:** 8 Feb 2007, 06:38 am »

Quote from: Destroyer of Smiles. on 8 Feb 2007, 06:09 am

How hard was the DAC to replace?

Hard. It's a surface mount part and takes considerable skill to remove without destroying the traces on the board. I hear that the SB3s sold today already have the upgraded DAC, so this is no longer needed.

Quote

Why 4.7uf on the output, would 10uf not be more appropriet?

For most preamps or amps that one would drive, 4.7uf is fine. With a 10K input impedance to the amp or preamp, it gives a 3.4hz cut off which is pretty low.

Quote

Does removing the OPAMP remove the ability for volume control? What OPAMP is it? (perhaps something better could be put in, if volume control is needed and an OPAMP to make it possible?)

Removing the op amp has no effect on the volume control - it still works fine. The op amp is an NJM2041.

Quote

Are schematics avalible for the SqueezeBox3?

http://www.audiocircle.com/index.php?topic=20977.msg325032#msg325032

GBB · « **Reply #9 on:** 8 Feb 2007, 06:42 am »

Quote from: JoshK on 8 Feb 2007, 06:35 am

Great job Gary! A great thread. I really like your controlled approach.

Thanks Josh - but its already a pretty old thread. I did most of this work more than 1 year ago. I haven't changed anything since I posted this other than get an even better linear supply off of ebay - an old HP lab supply. I've also changed my opinion and now think the digital output is beter than the analog outputs. But it seems to be system dependent. When I carried my SB3 to a friends house last summer, the conclusion was that the analog outputs were much better than the digital putput into a DAC. But in my system I like the DAC better. Synergy is hard to predict.

---Gary

Folsom · « **Reply #10 on:** 8 Feb 2007, 07:15 am »

Thanks for the information. That is good to hear the new ones come with a better DAC installed (I hope). Not that there is any kind insurance I will be able to get one. I am just looking at all possibilities.

2wo · « **Reply #11 on:** 11 Feb 2007, 03:15 am »

Gary,
I just wanted to say thank you for your work. This is just the kind of info I have been searching for. I will be implementing many of your mods as soon as I can bare to tear my SB out of my system...John

jhm731 · « **Reply #12 on:** 12 Feb 2007, 04:54 am »

Gary-

I don't understand the value of installing a shielded pulse and then running unshielded wire from it's output
pass the RF card to the output jack.

The SB3's ground plane is full of noise, IMO, it would be better to use an external ground source
for shielding and use two conducter cable with a shield for internal wiring.

PS- try the SC947-02.

GBB · « **Reply #13 on:** 12 Feb 2007, 02:18 pm »

Quote from: jhm731 on 12 Feb 2007, 04:54 am

Gary-

I don't understand the value of installing a shielded pulse and then running unshielded wire from it's output
pass the RF card to the output jack.

The SB3's ground plane is full of noise, IMO, it would be better to use an external ground source
for shielding and use two conducter cable with a shield for internal wiring.

Shields are good for blocking capacitively coupled noise. Twisted pairs, as I used here, are good for reducing inductively coupled noise. My assumption was that any RF flying around the inside of the Squeezebox would be picked up inductively, not capacitively, thus the twisted pairs.

---Gary

Folsom · « **Reply #14 on:** 1 Mar 2007, 04:59 am »

What do you guys think of this...

http://www.cimarrontechnology.com/index.asp?PageAction=VIEWPROD&ProdID=19

+

OPA627AUs?

I think it would even fit in the case. There is a possibility or changing the resistors that power the OPAMP but no big deal right?

Folsom · « **Reply #15 on:** 1 Mar 2007, 06:38 pm »

Nevermind that idea...

Question why does the unit have two DACs? the PCM1748 and the AK4384VT?

Does anyone have the Schematics for the display? (most it's inputs and outputs) and the input from the wall part, the DC in (5v)?

mgalusha · « **Reply #16 on:** 1 Mar 2007, 07:56 pm »

Quote from: Destroyer of Smiles. on 1 Mar 2007, 06:38 pm

Question why does the unit have two DACs? the PCM1748 and the AK4384VT?

It doesn't, at least the SB2 doesn't. The partial schematic that Sean Adams posted long ago shows two DACS and the pads exist on the SB2 board (haven't looked at my SB3) but the AKM chip isn't present.

Mike

Folsom · « **Reply #17 on:** 1 Mar 2007, 08:02 pm »

Yeah I was looking inside SB3 and the numbers for what is what is not even matching with the Schematic. Poo

Russtafarian · « **Reply #18 on:** 23 Apr 2007, 03:18 am »

I finally got around to modding my SB3. Thanks to those who posted in this thread, especially Gary, to get me moving in the right direction. It turned out to be more of a parts removal operation. First I replaced the PS cap with a 3,900uF Panasonic FM. I then removed the op amp, the input and output caps for the op amp, and the analog RCA jacks. I installed upgraded RCA jacks and connected the DAC outputs directly to the RCA jacks.

What! No coupling caps? Well I wasn't thrilled with the option of using tiny electrolytics due to the tight spacing so I decided to go outboard with the caps. Here's what I came up with.

Those are 4.4uF polypropelene clarity caps. And yes, the SB3 sounds wonderful in this configuration!

Russ