SB2 schematics + tweaking the digital output

[Builder Brad]

Hi

I have a Squeezebox2 that I am looking to mod.

I also have a second Squeezebox that was given the full works a couple of years ago by Vinnie at Red Wine Audio.

The plan is to use the RWA squeezebox as a baseline unit and see if I can improive on its performance, the thing is I only use this modded unit for its digital outputs into a relatively well tweaked Paradisea DAC, whilst the performance of the modded Squeezebox is very good using the analogue outputs, it does not sound as nice as when I use the Paradisea DAC and I would like to see if I can improve on this further by tweaking the second units digital outputs.

I will look to upgrade this SB2 in the following steps:

1)add Scientific Conversion SC947-02 1:1 transformer to the digital outputs - I am already using one of these transformers in the DAC and it has improved the sound considerably.

2)upgrade the power supply

3)swap the digital output connector for something better

and if at this stage I am getting close to the Rewd Wine Audio modded Squeezebox I will then look to removing parts, or all of the analogue output sections including unused power supply parts.

I really need a schemitic for the SB2 but I cannot find one on this forum

Can anyone help?

Brad

[crooner]

For my Super Squeezebox project I added the SC947-02 transformer (both stock inductors removed) with the shield connected to ground. This ground is also connected to the linear power supply's chassis.

The transformer is further shielded against EMI/RFI by a small section of Stillpoints ERS cloth on top.

I added a Neutrik true 75 ohm BNC connector (available from Markertek).

The super SB and power supply is further explained on my "Super Squeezebox" thread in the Audiophiles forum.

[Builder Brad]

Hi Crooner,

nice project, love the medical PS, do you feel the need to take this any further - as you are not using the analogue sections in the SB have you considered the benefits in removing/ disabling them?

do you have information, or schematics, on the SB2s digital output? - I can only find one inductor on the Pcb, although I have not looked in detail yet.

My original RWA Squeezobox had the full battery mods, which included seprate regulated 12v and 5v power. I was not completely happy with the battery power and finally settled on a custom version of the JSR04 power supply with seperate 5 and 12v sections:

http://sjostromaudio.com/_unsql/forsale/index.html

I have a spare 2-3 amp 5v power one PS that needs a little work which I was going to use on the new Squeezebox project - if I can better what I am hearing on the current RWA unit.

Brad

[Builder Brad]

looking at the pcb in a bit more detail helped to clear things up. I removed both inductors L2 and L5, and connected the primary (pins 5,8) on the transformer at the junction of R2 and R3 and earth, with the shields (pins 6,7)tied to ground. the output of the transformer is temporarily connected to the existing connector which has its earth issolated from the Squeezebox pcb.

it sounds crap

compared to the RWA modded unit

but I am still using the switching PS

here is the installed transformer image

http://www.audiocircle.com/gallery/albums/userpics/47836/DSC03366.JPG

[tomjtx]

I think all you guys should send me your modded units so I can do a shootout.
I'll only need them for,
Say for one year , or, two maybe :-)

[crooner]

Hi Brad,
Thanks for your comments re my project.

I considered getting rid of the internal analog section. However, I may have a need for the analog outputs in the future. Better leave 'em in there, just in case..

I think there's a small diagram floating around but not the actual schematic. This has never been published, if I am not mistaken.

To install the transformer I just pulled out both inductors and bridged the pads together. This allowed me to use the same output connecting points for the transformer, and therefore hardwiring the unit on the secondary side.

The primary side goes to a nearby empty connecting point where the WIFI antenna connector used to be (I moved it to the chassis). These pads are used to wire in the cable that goes to the BNC connector.


Hi Crooner,

nice project, love the medical PS, do you feel the need to take this any further - as you are not using the analogue sections in the SB have you considered the benefits in removing/ disabling them?

do you have information, or schematics, on the SB2s digital output? - I can only find one inductor on the Pcb, although I have not looked in detail yet.

My original RWA Squeezobox had the full battery mods, which included seprate regulated 12v and 5v power. I was not completely happy with the battery power and finally settled on a custom version of the JSR04 power supply with seperate 5 and 12v sections:

http://sjostromaudio.com/_unsql/forsale/index.html

I have a spare 2-3 amp 5v power one PS that needs a little work which I was going to use on the new Squeezebox project - if I can better what I am hearing on the current RWA unit.

Brad

[crooner]

I think all you guys should send me your modded units so I can do a shootout.
I'll only need them for,
Say for one year , or, two maybe :-)

LOL!
I don't think I would be able to part with mine (seriously addicted to the thing)!

[crooner]

I can't see your image.
The SB has a single ground plane, meaning that both analog and digital outputs share the same common ground.
This means that this ground is ridden with noise from both analog and digital sections including the internal switching power supply!
No wonder the unit sounds like crap!
If you are using the stock switching power supply, I suggest you float the shields.
I connected the ground from my SB to the one in my power supply which in turn is connected to the AC outlet ground. This should clean things considerably.


looking at the pcb in a bit more detail helped to clear things up. I removed both inductors L2 and L5, and connected the primary (pins 5,8) on the transformer at the junction of R2 and R3 and earth, with the shields (pins 6,7)tied to ground. the output of the transformer is temporarily connected to the existing connector which has its earth issolated from the Squeezebox pcb.

it sounds crap

compared to the RWA modded unit

but I am still using the switching PS

here is the installed transformer image

http://www.audiocircle.com/gallery/albums/userpics/47836/DSC03366.JPG

[Builder Brad]

try again with the image:

[Builder Brad]

the shields on the digital outputs are floating now as I removed the inductor between the digital output and ground.

I have also applied this mod to the Paridisea DAC with the 2 shield
pins on the transformer connected to ground via a .01uf ceramic cap - this was recomended by a member on Audio Circle who is also recomending that I do the same with this SB2 mod.

looks like I used the same placing for the transformer, the unused
wireless pads were a good fit.

just got to repair my Power One PS and then will see what happens

Brad