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GordyInMA-USA
2005-07-03, 10:15
Hello....

I have read a lot in this forum concerning all of the nuances of various power supplies for the SB2. Is there an area on this or some other forum that discusses "in non-techie" english, how the power supply for an SB2 works. I know that the one which came with the SB2 is a linear power supply that puts out 5 volts, DC.

How does this differ, from say..... putting four 1.2 volt, NMH batteries in series (4.8 volts DC) as an example?

Thanks for your understanding in helping me here.... Please be kind!

Patrick Dixon
2005-07-03, 12:35
A power supply is about slightly more than just getting the right voltage: you need it to deliver the right voltage at the right current. So the SB2 requires a PSU that delivers 5VDC at about 1A. Incidentally power (in Watts) is the product of voltage (in Volts) and current (in Amps).

So four little batteries in series is not going to be able to cope with the power requirement of an SB2, and even if it could a 1000mAh set of batteries could only deliver 1A for a hour before you had to recharge them.

AFAIK, the SB2 PSU is a switched-mode PSU, rather than a linear PSU. Switched mode PSUs are more efficient and usually smaller than linear PSUs, but can suffer worse high frequency noise from the switching process.

seanadams
2005-07-03, 13:11
AFAIK, the SB2 PSU is a switched-mode PSU, rather than a linear PSU. Switched mode PSUs are more efficient and usually smaller than linear PSUs, but can suffer worse high frequency noise from the switching process.

Actually it consists of FOUR switching supplies, a Cockcroft-Walton multiplier generating three different voltages, and THREE linear supplies, one each for various audio components. The external 2A supply is a red herring - it does not power the audio circuitry directly. Audio is powered by linear regulators inside the unit. Here's a block diagram:



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)



It should be obvious from the above that the place to attack the audio power supplies would be at the 14VDC internal supply or the two linear regs which drive the DAC and op-amp stages.

If you want to try a battery mod, I would suggest cutting the trace feeding the 14V supply, and attaching a 14-18V battery pack there. If you try to feed the 5V input from a battery pack you will just drain your batteries VERY quickly with no improvement to the internal audio power supplies.

Triode
2005-07-03, 14:56
Sean - So digital output fans could use the 3.3V linear headphone supply for the 74hc04 oscillator and output buffer...??? [grounding permitting]

seanadams
2005-07-03, 16:12
Sean - So digital output fans could use the 3.3V linear headphone supply for the 74hc04 oscillator and output buffer...??? [grounding permitting]

Sure, or just mount another one dead-bug-style on top of it.

pfarrell
2005-07-04, 08:47
On Sun, 2005-07-03 at 10:15 -0700, GordyInMA-USA wrote:
> Is there an area on this or some other forum that discusses "in non-techie" english,

I don't think such an answer is possible.
In more of the universe, power supplies are black boxes.
One kind of power comes in, and another kind flows out.

Many audiophiles love to get geeky. (Other just want
to listen to music).

It is reasonable to suggest that the powersupply
in an inexpensive component (such as a SB2) is
inexpensive. Thus you can postulate that
a "better" powersupply could perhaps make
the SB2 sound better.

But from there it gets hard into electrical engineering.
What is "better" in what areas? what specs are needed.

Sean posted some details about how the SB2 really needs
four kinds of power. Unsaid is which of those,
if all four, three out of four, etc.
are most important to what kind of sound.

For me, I just listen.

--
Pat
http://www.pfarrell.com/music/slimserver/slimsoftware.html

NealG
2005-07-04, 09:40
> Is there an area on this or some other forum that discusses "in non-techie" english,

I don't think such an answer is possible.
In more of the universe, power supplies are black boxes.
One kind of power comes in, and another kind flows out.

Many audiophiles love to get geeky. (Other just want
to listen to music).

It is reasonable to suggest that the powersupply
in an inexpensive component (such as a SB2) is
inexpensive. Thus you can postulate that
a "better" powersupply could perhaps make
the SB2 sound better.

But from there it gets hard into electrical engineering.
What is "better" in what areas? what specs are needed.

Sean posted some details about how the SB2 really needs
four kinds of power. Unsaid is which of those,
if all four, three out of four, etc.
are most important to what kind of sound.

For me, I just listen.




Pat, Sean has stated which one, the 14VDC supply to the audio stages. Also Andrew pointed out the same in another thread. I agree though, some times you just want to listen and adding a dedicated 14V supply is going to involve warranty breaking surgery ;) However, unless somebody tries nobody will know and we will postulate even more ;)

occam
2005-07-05, 10:51
Sean,

Its quite refreshing to the CEO being so supportive and open with those seeking to modify his product.

So you've gots to get an external powersupply that provides regulated 5vDC and 14vDC. (or that 14vDC could be changed to a charger for a 12v SLA, assuming the dropout voltage of the 2 linear regulators it would feed [to the analog circuitry] allows it. You've got to cut a trace to route your 14vDC in, and void the SB warranty....

So you need a multibobbin power transformer, not a toroid, bridge(s) [and doubler depending on transformers secondary], ic or discrete regulators and caps.... As you're using a proper transformer with low capacitve leakage and limited bandwidth, you might as well front that with a single small balancing transformer and appropriate capacitive filtering between, and drop the noise going in, and out.

Obviously this hack isn't going to come with UL certification so you need a grounded mains plug, and inevitably we've line noise and grounding issues. I'm a great believer in brute force filtering and symmetrical power for both analog and digital circuitry, as long as you can source inexpensively enough. Which is the sole advantage of the diy community. We can buy surplus crap.

Suggestions?
What are the 3 pin linear regulators feeding the DAC and opamps?
Is the output NJM2041m running single rail with the output electrolytics biased @ +4.5vDC?

Many thanks in advance,
Paul

max.spicer
2005-07-05, 12:21
You know, I think I understood at least half the words in that post. :-)

Max


Sean,

Its quite refreshing to the CEO being so supportive and open with those seeking to modify his product.

So you've gots to get an external powersupply that provides regulated 5vDC and 14vDC. (or that 14vDC could be changed to a charger for a 12v SLA, assuming the dropout voltage of the 2 linear regulators it would feed [to the analog circuitry] allows it. You've got to cut a trace to route your 14vDC in, and void the SB warranty....

So you need a multibobbin power transformer, not a toroid, bridge(s) [and doubler depending on transformers secondary], ic or discrete regulators and caps.... As you're using a proper transformer with low capacitve leakage and limited bandwidth, you might as well front that with a single small balancing transformer and appropriate capacitive filtering between, and drop the noise going in, and out.

Obviously this hack isn't going to come with UL certification so you need a grounded mains plug, and inevitably we've line noise and grounding issues. I'm a great believer in brute force filtering and symmetrical power for both analog and digital circuitry, as long as you can source inexpensively enough. Which is the sole advantage of the diy community. We can buy surplus crap.

Suggestions?
What are the 3 pin linear regulators feeding the DAC and opamps?
Is the output NJM2041m running single rail with the output electrolytics biased @ +4.5vDC?

Many thanks in advance,
Paul

seanadams
2005-07-05, 12:22
Sean,

1) You've got to cut a trace to route your 14vDC in, and void the SB warranty....

2) So you need a multibobbin power transformer, not a toroid, bridge(s) [and doubler depending on transformers secondary], ic or discrete regulators and caps.... As you're using a proper transformer with low capacitve leakage and limited bandwidth, you might as well front that with a single small balancing transformer and appropriate capacitive filtering between, and drop the noise going in, and out.

Suggestions?
3) What are the 3 pin linear regulators feeding the DAC and opamps?
4) Is the output NJM2041m running single rail with the output electrolytics biased @ +4.5vDC?



1) Small correction: it's actually 12.5-13.0V after the filter, at the input to the regulators.

2) I don't know that an external supply is absolutely necessary. Equally good results might be achieved by replacing those two regulators with either high performance integrated regulators or Andrew's super regs. I haven't tried either yet myself, but when I do I'll share some numbers.

3) They're Texas Instruments UA78L05ACPK and UA78L09ACPK. Minimum dropout is 2.5V.

4) Correct

Michel Fombellida
2005-07-05, 12:34
I should soon (next week I hope) receive an external PS based on the principle mentioned by Sean. The tweaker analysed what he saw inside the SB2 and of course came out with the same circuit as mentioned by Sean. He decoupled the different elements inside the PS and will power them externally (at least those critical for audio). BTW, he also added word clock inputs. I hope to be able to soon post more info.

Michel

occam
2005-07-05, 16:04
Sean,

Thanks for the quick response. Certainly, scarce resources might be better spent on digital clocking, reconstruction filters, etc...
Six months ago I firmly believed powerconditioning, balancing and such were appropriate only for products with poor, inaccessable powersupplies. I've changed my opinion after much empirical work; surely a sign of more free time than common sense.

Thanks again,
Paul

GordyInMA-USA
2005-07-07, 18:30
Ummmm Errrrr...... Geee guys... I really appreciate all of this, but it's way over my head! All I wanted to do and still want to do is come up with an inexpensive means to power my SB2 with some kind of battery power to make it truly wireless. If I could, I could couple it with a nice set of battery powered speakers and have a ball with awesome wireless music on my back deck as well as anywhere in my yard!

GordyInMA-USA
2005-07-07, 18:40
Gentlemen and Ladies!!!

I mean .... just rlax, sit back and think of it ... really!

Having available a reasonably priced, efficient battery power supply for the SB2 (and SB, if possible) would have people literally gobbling them up! A truly wireless Squeezebox!!!

In additon to this, come up with an awesome battery powered speaker (system) that would be designed as a perfect match AND companion for the SB2 (and SB, if also possible). Include within it a decent set of Base, Midrange and Treble controls.... it boggles the mind!

This could bring Slim Devices into the next level!

I am really serious about this!

seanadams
2005-07-07, 19:32
Ummmm Errrrr...... Geee guys... I really appreciate all of this, but it's way over my head! All I wanted to do and still want to do is come up with an inexpensive means to power my SB2 with some kind of battery power to make it truly wireless. If I could, I could couple it with a nice set of battery powered speakers and have a ball with awesome wireless music on my back deck as well as anywhere in my yard!

Heh... you should have said the goal was to make it portable - we thought you were wanting to hot-rod the audio outputs. You posted in the audiophile forum. Audiophiles have been known to go as far as using BATTERY POWERED CABLES in pursuit of better sound. :)

Anyway to answer your question: you will need a 9-15V battery (your choice depending on run-time required, rechargeability etc) and something like this to generated regulated 5VDC for the Squeezebox2:

http://www.powerstream.com/dc6.htm

For the choice of battery: you will need something fairly big. A 12V lantern battery would give you about 20hrs of run-time by my estimate. If you just need 1-2 hrs you could use something like the 14V power pack for a cordless power tool or a remote controlled car.

ackcheng
2005-07-12, 09:39
Is it true that if one is using SB2 digital out only, there is not advantage in changing to a better PSU? Becasue the info passes out to the coax is bit accurate?

Changing the PSU can only affect the analog part ie. the DAC and Opamp??

Aylwin
2005-07-13, 00:12
My opinion to that would be yes, yes and yes. But like Sean says audiophiles can be pretty, uhm.... eccentric. :)

Michel Fombellida
2005-07-13, 00:44
Not true because the Power Supply can induce noise inside (BTW even outside) the unit that will impact the digital outputs as well (impact on the jitter for example). Bit-exact is not the only thing to consider for an audiophile system.

Michel

Patrick Dixon
2005-07-13, 00:46
Your opinion would not be entirely correct, since the PSU can also affect the clock (oscillator). Whether you consider this analogue or digital, is entirely up to you!

Aylwin
2005-07-13, 03:06
It's true that the power supply could probably have an affect on jitter. How much, I think is arguable. At least it would be nice if someone could measure it. Still, I doubt the difference (if any) would be audible.

Personally, I'd much rather focus on the DAC end. Meaning, improve the power supply, deal with jitter and do other tweaks on that end.

Patrick Dixon
2005-07-13, 04:31
Meaning, improve the power supply, deal with jitter and do other tweaks on that end.The problem being that the jitter performance of the DAC is only as good as the clock you're feeding it, and if you are deriving that clock from a 'jittery' signal, you are making your job that much harder.

CardinalFang
2005-07-13, 04:44
Anyway to answer your question: you will need a 9-15V battery (your choice depending on run-time required, rechargeability etc) and something like this to generated regulated 5VDC for the Squeezebox2:

http://www.powerstream.com/dc6.htm


Slightly off the subject of battery supplies, I'm planning to re-house my SB2 in a new aluminium enclosure and I'm considering building a PSU into the same enclosure. Is there any off-the-shelf 5V regulated PSUs that anyone would recommend, or should I stick with the wall wart one? I'm using digital outputs, but still want to make sure the circuits are getting a clean supply.

thanks

Paul

Aylwin
2005-07-13, 04:58
True... if you're DAC relies on the incoming digital signal for that. I guess it depends on the DAC you're using and the type of tweaks you're going to do.

If you use a DAC with its own clock then you don't need to be synchronised with the source and you can then pass the incoming signal through a buffer and then re-time the signal with you're own clock. I believe this is what the Benchmark DAC1 does (someone please correct me if I'm wrong).

Another option is to use a box like the JISCO which, well, it's better if they explain: http://www.jitter.de/english/jiscofr.html.

Yet another possibility is to really sync your source and DAC by feeding the clock signal from the DAC via a dedicated cable back to the source. This requires more serious modding though.

I guess my point is that, IMHO, upgrading the power supply will provide minimal (if any) improvement. There are other things you can do which will have a more significant impact. In fact, I think upgrading the internal power supplies of the SB2 itself would be better than just the AC adaptor. However, simply replacing the power adaptor would be simpler and cheaper than the other things I've suggested so I guess it's not that big of a deal. I just wouldn't expect any improvements to be much of a deal either.

Aylwin
2005-07-13, 05:07
I'm considering building a PSU into the same enclosure. Is there any off-the-shelf 5V regulated PSUs that anyone would recommend, or should I stick with the wall wart one?
For this, I'd recommend an internal linear PSU. I don't know about off-the-shelf ones but Andrew has made one here: http://forums.slimdevices.com/showthread.php?t=14374&page=2&pp=10 Perhaps you could make something similar to fit in your enclosure.

P.S. I'm soooo busy at work today. ;)

ackcheng
2005-07-13, 11:20
If jitter is coming from the PSU. Howabout this mod

Change the stock switching PSU to a linear regulated PSU 5V, 2A
Then, change the original oscillator to Elso clock or Tent clock which are supposed to have very low jitter. Would this work?

The only think I am concern is that there are still some switching for the production of other voltages from this 5V, 2A for SB2 to work.

CardinalFang
2005-07-14, 01:38
For this, I'd recommend an internal linear PSU. I don't know about off-the-shelf ones but Andrew has made one here: http://forums.slimdevices.com/showthread.php?t=14374&page=2&pp=10 Perhaps you could make something similar to fit in your enclosure.

P.S. I'm soooo busy at work today. ;)

Thanks for that, I'll have a mooch around on the interweb to see what I can find. I did post the link to the case on this thread

http://forums.slimdevices.com/showthread.php?t=15009

It's fairly slim in height, so I'll need to pick carefully.

Vinnie R.
2005-07-14, 05:41
Thanks for that, I'll have a mooch around on the interweb to see what I can find. I did post the link to the case on this thread

http://forums.slimdevices.com/showthread.php?t=15009

It's fairly slim in height, so I'll need to pick carefully.

CardinalFang,

If you are looking for a high quality linear 5V supply, I highly recommend you check out this one:
http://www.acopian.com/single-l-pcb-1to9vt.html

Model 5E150 is 5V, 1.5A and will do the trick

Here is a pic:
http://www.acopian.com/single-l-pcb-p.html

Here are dimensions:
http://www.acopian.com/single-l-pcb-d.html

They aren't cheap, but I am using one now and the improvement is quite noticeable!

The one I'm using is this one:
http://www.acopian.com/single-l-screw-p.html

but you'll probably need the PC-mount version because it is a little slimmer....you certainly have a space restriction!

Good luck!

Vinnie

CardinalFang
2005-07-14, 09:09
CardinalFang,

If you are looking for a high quality linear 5V supply, I highly recommend you check out this one:
http://www.acopian.com/single-l-pcb-1to9vt.html

Model 5E150 is 5V, 1.5A and will do the trick
Vinnie

Thanks for this - I'll see if they ship to the UK.

Paul

Vinnie R.
2005-07-14, 11:36
Thanks for this - I'll see if they ship to the UK.

Paul

For use in teh UK, look like you want to go with this option:

"230 Volt Input: All models can be alternately furnished for operation on an input of 210 to 250 VAC, 47-420 Hz. To order, add suffix "-230" to model number and $10.00 to price. The "-230" option requires two additional days."

Not sure if they ship to the UK, but they probably do!

Michel Fombellida
2005-07-14, 12:08
Here are three pictures of a modified SB2 with an external PS with independant lines for the different internal voltages (decoupled internally) and 2 word clock inputs.

I should get it back from the tweaker quite soon.

Michel

seanadams
2005-07-14, 18:06
Where are the word clock inputs?

occam
2005-07-14, 19:52
Hey Vinnie,

Those Acopians are certainly small and well specified. Have you compared their subjective performance to the less expensive and multisourced linear supplies such as those from Power-One, Condor, International Power, etc...?

TIA,
Paul

Michel Fombellida
2005-07-15, 01:22
Hi Sean,


Where are the word clock inputs?

They are the 2 little boards that are attached to the inside of the top cover of the SB2, there is one for 44.1khz multiples and one for 48khz multiples. There is also a switch (it will be on the side of the SB2) to disable them and go bact to the internal clocks.

Vinnie R.
2005-07-15, 06:57
Hey Vinnie,

Those Acopians are certainly small and well specified. Have you compared their subjective performance to the less expensive and multisourced linear supplies such as those from Power-One, Condor, International Power, etc...?

TIA,
Paul

Hi Paul,

I have not compared my Acopian to the other power supplies you mentioned. The Acopian is not cheap, but they are very small and very clean! Using the Acopian instead of the stock switching supply makes a very noticeable audible improvement to me.

I also loaned one to a friend of mine who brought my attention to the SB2. Here is what he wrote to me:

"There is NO question that the power supply makes a noticable
difference. Very noticable, I'd say. Smoother, sweeter. Much less
hardness (particularly with strong transients). Women's voices like Bjork now sound like they are "singing forcefully" rather than shouting. Makes it so much better to listen to and appreciate."

I totally agree, but I'm no longer using the Acopian...I switched over to battery power and am even happier. See my post here:
http://forums.slimdevices.com/showthread.php?t=14751&page=2

Regards,