SB3 - PSU upgrade, which one of these replacement wall warts?

[Phil Leigh]

It is not an inductor. It is a ferrite bead. Yes, it reduces EMI. It screws up the output impedance. Simple as that.

Pat

Pat - understood. I read your stuff on this. What I'd like to know is... what effect - if any - would you expect on the performance of the spdif out by removing the bead? I'd expect it to be highly DAC-dependant. Some DAC's would repond favourably, whereas others wouldn't care.

[ar-t]

Been busy with taxes, and other stuff. Time has been at a premium.

Can't say with 100% certainty, but as you already suspect, it is dependent on how the DAC deals with incoming jitter.

As an example, and excuse me if I rant needlessly, but a recent review in one of the big magazines, shows the jitter from the review unit into 2 different DACs. The one that has a ASRC handles it fine. The other has no ASRC or secondary PLL. The jitter is horrible. The reviewer alludes to the DAC is supposed to deal with the jitter.

I guess that means that all of these USB kludges can spew out anything, and if your DAC can't handle it, then it is your problem. Somehow I suspect if one of our clients made one of these kludges, it would get panned. Not so if you pump $$$$$$$$$$$ in advertising.

I have noticed some of the posts (some in other threads) ask about how all of these outboard supplies affect sound. Especially on the SPDIF output.

I can measure differences on the SPDIF output on the SB3. Hard to see a difference on the Duet. That can easily be explained by the supply architecture. Does not mean that it won't sound different, but only that I can not see it.

Now, if you modify the internal supply, and do some other things to the clock, there are differences. However, to see them, one has to look at the recovered clock at the DAC. So, while I can not see them in the output, you can see it at the far end.

But, as before, how much of a difference that can be seen is a function of the DAC, and how it deals with jitter.

I would like to point out that there are many designers who feel that while ASRCs deal with jitter that they affect the sound in negative ways. Just an opinion. Everyone has different expectations.

Pat

[IvRak]

I'm a relative newcomer to the Squeezebox arena (Squeezebox 3/Classic), but I have made a few observations.

Having a good quality coaxial cable, with correct impedance, is a good idea. The first few days I ran the digital output throuh a normal signal cable for line out. It sounded fine, but when I got a prober coax digital cable to replace it with, the treble became more open, and a little less harsh.

But the big improvement I found, was in modifying the Power Supply, that came with the Squeezebox.
I took it with me to work, and measured it. Allthough it had a stable voltage of 5.12V, I could see a little ripple or noise on an oscilloscope. This was very low level ripple (on an unloaded power supply).

So I added a couple of electrolytic capacitors, 16900 uF all together, in parallel over the Power supply (there now was no measureable ripple, at least none that my equipment could measure).

When I got home I hooked the modified Power supply up to the system.

This modification had made quite a difference, I was actually a little shocked at how much.
Everything is clearer, the treble is much more open and precise (and less harsh), midrange sounds softer, and bass has more punch.
The capacitors actually hold enough power to keep the Squeezebox running for 1-2 seconds after I pull the plug from the wall...

I think the difference in sound must come from the noise present in the unmodified power supply, finding its way to the DAC in my Surround receiver. I don't think the digital signal tranmitted is different, except perhaps for a little less jitter?

Off-course I could be imagining it, or exagerating a tiny change, but I'm convinced that a better power supply is the best way to improve the Squeezebox's sound.

I will begin constructing an even better, passively regulated supply (transformator, rectifier bridge, capacitors, nothing more), for future use.

[tyler_durden]

"Passively regulated" is marketing BS for unregulated.

Good luck with that.

TD

[IvRak]

Thanks?

Being an electronics technician, I think I can make it work.

If I have to put some sort of regultion into the supply, I can live with that, it just has to be done proberly.

But taking a good transformer with more than enough VA (and the correct output voltage), putting a rectifier bridge on the output, then some condensators, and perhaps a couple of diodes in series to regulate the voltage, and then perhaps even more condensators, should make it possible to reach 5V reasonably precisely.

And with enough capacity in the condensators, it will perform beautifully. Will probably not be cheap though.

[Greg Erskine]

hi IvRak,

If you decide to go down that track make sure you have reasonably steady mains voltage. What is the minimum input voltage that the SB will still function?

Also, you might use a RCRC arrangement to drop a little voltage and provide better fitlering as a bonus.

regards

[OutdoorXplorer]

I am pairing my SB3 with a Welborne PSU and the difference is pretty dramatic. The soundstage open up and bass is better control too.

[IvRak]

I dont know the exact minimal voltage, but that would be easy to find, with a variable power supply.

Mains in my area are specified as 230V +/- 10% (its at 224V this moment). So if I hit 5V at 230V, a 10% change in any direction would result in 0.5V change.
This would probably be at or past the limits of what the Squeezebox accepts.

So I will probably have to do a little regulation, but thats not a problem, if done proberly.

I have a mains filter in front of the power supply, I think it catches most of the mains noise going into the PSU.

[Phil Leigh]

I dont know the exact minimal voltage, but that would be easy to find, with a variable power supply.

Mains in my area are specified as 230V +/- 10% (its at 224V this moment). So if I hit 5V at 230V, a 10% change in any direction would result in 0.5V change.
This would probably be at or past the limits of what the Squeezebox accepts.

So I will probably have to do a little regulation, but thats not a problem, if done proberly.

I have a mains filter in front of the power supply, I think it catches most of the mains noise going into the PSU.

You need a 5V REGULATED supply.

By the way, that "ripple" you observed on the PSU... did you ever check what happened to that ripple when you connected the PSU to the Squeezebox... ?

IME (and well-documented tests) there is nothing to be gained from changing the SB PSU if using the digital outputs, however:


If you are using mains filters, you should put one on the SB PSU AND one on your AV receiver.

Filters work both ways - in and out. However, some work better in one direction than the other...

You should also really investigate using TOSLINK cable instead of S/pdif coax, if your AV receiver supports it.

[IvRak]

Phil Leigh:

I didn't bring my Squeezebox to work, only the PSU, so I didn't measure it with load. I know Switch mode supply's often meassure worse without any load. Perhaps that's why it meassured better with the condensators attached, they would provide a _small_ load (as well as help remove ripple).

I didn't expect any changes to the sound, but I'm pretty convinced they are present. The Squeezebox has been more pleasant to listen to since the modification.

I have separate mains filters for Amplifier, CD-player and Squeezebox. Actually the CD-player and a Minidisc share one, but thats beside the point.

Going Toslink is also something I'm considering, but the only test I've made didn't show much difference between the two. But this comparison was with good quality coax against a very cheap factory delivered (with minidisc) tos-link, so perhaps not a fair comparison

Will experiment some more, thats also where the fun is at in playing with audio equipment...