[JoshK]

First off I want to say, this thread isn't meant as a stab to the couple of pro modders on this site.  They offer a turn-key solution for those that don't want to learn or both with modding/diy.   I vaguely understand what they are doing and it is sound IMO.  This thread is meant for those of us that would rather drink amonia than to not DIY.  

I got my grubby hands on a SB2 a while back but computer hiccups have slowed my progress in getting it online.  So I haven't even heard it stock yet and already I am discussing modding it.  Well that is what us few neurotic DIYers do, don't we?

So shall we make a list of items to tackle?

1)  This most certainly has to be the PSU.  That crappy tiny little wallwart has to go.  Heck there are many off the shelf upgrades that will work in lieu of this wallwart with improving results.  Any industrial regulated 5V supply will be an upgrade to this.  I happen to have two variants of these in my possession.  

The simplest and probably most cost effective way to do the PSU might be to take said industrial supply (corcom, et al) and do some part swapping.  Change out the diodes to some uber fast soft rec type, swap out the regulators to something more manly and replace caps with whatever is currently in fashion.     Viola, easily <$100 and probably very effective.  Heck, might want to add a "Felicia" or "Beguine" in front of it in the same box and have a full solution to plug into wall.

2)  Next up, per Sean's own admission the DAC is currently providing polarity correctly and the opamp is inverting polarity, so bypassing the opamp will keep polarity absolute and provide all the benefits of a shorter pass, etc.  Bypass with caps from the DAC to RCAs is one solution.  Upgrading the opamp is another.   We should discuss options.

3) Clock??

Anyway, that is enough to get the ideas flowing.

[Al Garay]

Glad you finally got one. You really need to solve your connection problem and listen to it in stock form. It's quite good as is.  I have the SB1 version and will be interested in mods.

thanks,

Al

[goskers]

I am definitely game for this one  

I am looking at just getting the best possible digital feed from the unit.  Starting with replacing the main cap would be the easiest.  Building or modding an outboard ps would be the next step.  

If I get time I will take my SB2 apart and look under the hood.

[Vinnie R.]

First off I want to say, this thread isn't meant as a stab to the couple of pro modders on this site. They offer a turn-key solution for those that don't want to learn or both with modding/diy. I vaguely understand what they are doing and it is sound IMO. This thread is meant for those of us that would rather drink amonia than to not DIY.

Hi JoshK,

Thanks for stating that up front  

1) This most certainly has to be the PSU. That crappy tiny little wallwart has to go. Heck there are many off the shelf upgrades that will work in lieu of this wallwart with improving results. Any industrial regulated 5V supply will be an upgrade to this. I happen to have two variants of these in my possession.
...

This might help you all out with item 1 that JoshK listed:

If you want to replace the stock wall-wort SMPS, you should check this one out:

http://www.acopian.com/single-l-screw-p.html

See model 5EB100, 5EB150, etc. (don't go lower than 5V, 1A).
http://www.acopian.com/single-l-screw-1to9vt.html

I have a couple here and initially used it to replace the stock supply...nice improvement for $100!    They are clean (less than 1V rms ripple).

I also posted this in the following thread (this is helpful to know if you want to really clean up the critical power supply section to the internal dac and spdif output circuitry):
http://www.audiocircle.com/index.php?topic=20800&postdays=0&postorder=asc&start=10

I've received a few emails asking if I can just mod the SB2's analog and digital output, and leave it to the customer to supply their own 5V linear power supply. Sure, this can be done and will certainly reduce cost, but keep in mind that with the Red Wine Audio SB2 mods, not only do I supply a regulated 5V line (regulated off the 12V SLA) to the SB2, I also do the following mod (I'm not sure if other modders are doing this or not):

Removal of the 14V power feed from on-board switching power supply (which feeds the critical 3.3V and 5V regulators used for the internal DAC as well as the SPDIF output buffer), and replace it with the 12V supply line from the external 12V SLA battery enclosure...a much cleaner choice!

This takes the sonic improvement of my analog output stage mods to the highest level, and the 12V SLA that feeds the regulators yields a cleaner supply to the digital output section.

To summarize, the battery enclosure outputs 5V and 12V to the modded SB2 (note the custom 3-pin connector on the umbilical coming out of the modded SB2). The stock SB2 only has a 5V input, and uses a noisy internal switching power IC that provides 14V to the critical 5V and 3.3V regs used for the analog (internal dac) and digital output section. I replace this switching IC with a direct 12V feed from the SLA.

You can always get a 12V Linear supply for this.  The cleaner the supply, the better the results.

Have fun with it!  

[JoshK]

I am definitely game for this one  

I am looking at just getting the best possible digital feed from the unit.  Starting with replacing the main cap would be the easiest.  Building or modding an outboard ps would be the next step.  

If I get time I will take my SB2 apart and look under the hood.

Actually, like you Joel, I am going to use this via digital output into my DEQX so I think for us all the best place to start is with the PSU.  Another thought is adding a digital output transformer.  Good things came about with the CDPro2 kit when a DOT was added, why not here too?

Thanks Vinnie for adding your comments.  What a great sport!  I like your idea of upgrading the internal 12V switcher too.  Great idea and I'll probably examine that too.  

SLAs are cheap these days and I have a few chargers for them as it is.  I would like to keep everyone in the loop who wishes to participate and not go after unobtanium for this project, so if we go SLA we also need to come up with a good charging solution.  

Vinnie provides links to regulated supplies and I have a couple regulated supplies in my possession, one a standard corcom industrial regulated supply (5V 3amp) which is on the surplus market for a whoppin' $3.50.  This would provide a nice cheap base from which to mod.  I also have a beast of table wart (thanks to Occam!) that is a regulated 5V supply.  

I will soon try to do some comparisons and see what you guys wish to persue as well.  

Like Vinnie said

Removal of the 14V power feed from on-board switching power supply (which feeds the critical 3.3V and 5V regulators used for the internal DAC as well as the SPDIF output buffer), and replace it with the 12V supply line from the external 12V SLA battery enclosure...a much cleaner choice!

I'd like to explore this too and I'm not afraid to hack it open.

[JoshK]

I lied, it isn't a Corcom, it is a Power-One but at any rate it is a standard issue regulated supplie

link

[kfr01]

I'd like to see work on bypassing the opamp w/ a cap from the dac to the rcas.... and anything else to make the analog output as good as possible.

[CornellAlum]

I'd like to see info on the digital section, as I will not be using the analog whatsoever.  I imagine a few cap changes here and there will do wonders.

[randytsuch]

What about using a battery for the power supply?

Otherwise, it is pretty easy to build a linear PS.  Just takes a transformer, a diode bridge, a few caps and a linear regulator like a 7812.  If you use hex freds for the bridge diodes, and good quality caps, I think it would better most supplies you could buy.

I am thinking about getting one of these in the near future, looks pretty interesting.  I already have a wireless network at home, and a bunch of music ripped to a hd, and hd's are so cheap no, no problem getting more storage if I need it.

I am thinking I would use the internal DAC and volume pot, and run it straight to my amp.

The modders seem to be swapping out some caps with panasonic FC's.  I am partial to blackgates, but they cost more, and may soon really be going obsolete.

I would also bypass the opamp, just be a cap between the dac and RCA's.  I don't know if you need a resistor too, to make a filter for high frequency noise.

Just my random thoughts on the subject.

Randy

[Wayne1]

Just a few notes for those thinking about modding the SB2 themselves.

With the exception on the main 14 volt line cap, all the parts on the SB2 are surface mount. I do suggest you be very careful working in there.

You WILL need a variable temp soldering iron if you plan to replace any of the stock connectors. The ground connections take a LOT of heat to desolder while the SMT parts need very little.

Mounting of aftermarket RCA panel mount connectors can be a challenge.

The screws for the case are torx, not philips or slotted.

There is not a lot of room inside the case for large film coupling caps. Placement is fairly important if you want to get the case back together.

Practice attatching and securing leaded components to SMT pads.

If all this sounds like it may be too much for you, give Vinnie or I a call and keep your stress level down

[Vinnie R.]

Practice attatching and securing leaded components to SMT pads. ..

Yes, Wayne hit the nail on the head...practice!  If you are new to surface mount soldering, try to find junk boards that have surface mount parts all over them, and practice desoldering and soldering components.  It is very easy to lift a pad on the board if you are not careful.

[Occam]

Courtesey of Sean Adams, CEO of Slim Devices -

The powersupply block diagram-

Code: [Select]



AC  ->  5V 2A  -----> Dual      ----> 3v3 (IO, wireless, logic)
        SMPS    |     Switcher  ----> 1v2 (CPU core)
                |
                |----> Linear reg ----> 3v3 (headphone)
                |
                |
                |----> Switcher ----> Multiplier -----> 11VAC VFD ef
                                         |    |
                                         |    |
                  14VDC                  |    |-------> 55VDC VFD vdd2
                ----------RC filter<-----|    
                |
                |
                |------> Linear reg ---> 9vdc (op-amps)
                |
                |------> Linear reg ---> 5vdc (DAC)


The 5 & 9v linear regulators are Texas Instruments UA78L05ACPK and UA78L09ACPK

Tha output stage -
http://www.seanadams.com/dac.pdf
Note that the AKM4384 shown in the PDF  is not used or populated....
The dac is a BB PCM1748 and the opamp(s) is a dual NJM2041m.

[Vinnie R.]

Something doesn't look right....the 1748 dac is fed by 5V Vcc (analog) and 3.3V Vdd (digital).  They both come from regulators that are fed from the 14Vdc.

[Bingenito]

Is anyone planning on putting the SB2 into a nice chassis with the power supply(s)?

1.) There would be more room for components
2.) No outboard power supply
3.) The SB2 would no longer look like a cheap cable box (not that it matters)

[Occam]

Something doesn't look right....the 1748 dac is fed by 5V Vcc (analog) and 3.3V Vdd (digital).  They both come from regulators that are fed from the 14Vdc.

I'm just reposting from Sean. I've already asked Sean where the Vdd for the 1784 comes from.....

[randytsuch]

Anybody know where to get an internal picture of the SB2?

Randy

[JohnnyLightOn]

Here's one for ya:

http://www.slimdevices.com/photos/inside_squeezebox2/

Maybe others can post some with better details.

[randytsuch]

Here's one for ya:

http://www.slimdevices.com/photos/inside_squeezebox2/

Maybe others can post some with better details.

Thanks
between the schematics and pics, I can get an idea of what's going on.

Randy

[Occam]

Something doesn't look right....the 1748 dac is fed by 5V Vcc (analog) and 3.3V Vdd (digital).  They both come from regulators that are fed from the 14Vdc.

Per Sean Adams, CEO of SlimDevices

Digital side of the DAC is powered by the digital 3v3 rail from the switcher. You could move it to the headphone amp if you want.

Apparently, the 3.3Vdd for the DAC is not coming from a separate regulator off the 14Vdc rails, but is coming off the switching regulator (the 1st regulator shown in the above diagram) which is also powering a slew of other stuff. Moving it to the linear regulator powering the headphone amp, assuming it is of sufficient quality and quantity, might be a good idea.

[Vinnie R.]

Apparently, the 3.3Vdd for the DAC is not coming from a separate regulator off the 14Vdc rails, but is coming off the switching regulator (the 1st regulator shown in the above diagram) which is also powering a slew of other stuff. Moving it to the linear regulator powering the headphone amp, assuming it is of sufficient quality and quantity, might be a good idea.

Hi Occam,

Thanks for getting in touch with Sean Adams and clearing this up!

Regards,