Well, all these reasons hold for external smps. But there are also dozens of smps modules from reputable brands (not ebay dubious stuff) ready made to be put inside your equipment. I share your dislike for psu outside the device. But I'm seriously considering using encapsulated smps modules for some new designs. For low power, pricing really isn't bad. See: http://www.mouser.be/Power/Power-Supplies/AC-DC-Power-Modules/_/N-dv0g5/
Jean-Paul, I do not agree to all your points but you say sensible things. I just want to mention one other: with supplies like the SilentSwitcher you have the option to work completely off the mains (using a Power Bank). That is attractive because it it is often difficult to completely eradicate mains noise and hum, common mode noise through the PE connection etc. especially in installations with many pieces of equipment. Even when you don't hear mains junk it is often still high enough to mess up a measurement if you are in that sort of thing.
The other point is that there is always a certain danger if a diy-er starts to work with mains powered supplies. Many are well aware and make almost fool-proof supplies, but not all. A mains-free solution is also attractive hear.
Jan
The other point is that there is always a certain danger if a diy-er starts to work with mains powered supplies. Many are well aware and make almost fool-proof supplies, but not all. A mains-free solution is also attractive hear.
Jan
Again the need to design a PCB to mount one of those modules....and what is inside them ? Do they perform well enough for audio devices ?
BTW what is the definition of "low power" ? I mean , for me power amps are not low power devices. I think of tuners, DACs etc. all under 10 VA.
Performance wise it will be that way but at a cost ! Still I want convenience and a tidy audio corner or whatever it is called in english. It seems I am not alone thinking like that. I also want true mains isolated devices when I don't use them. All possession of too much stuff is ballast for the soul IMHO, the less the better.
Not only the forced habit to charge a phone (please note the severe lack in discipline in general with people and charging batteries) but now also a power bank with crappy micro USB connector. As usual the battery is depleted when you want to listen ....if the device hasn't already stopped working that is as its made to be cheap with only the Amperage number as a criterium...10.000 mAh !!! Still always depleted when you want to use it. Then the need to wait till it is charged as we are techies and do things right so we charge it to 100%...Now where is that charger ? Ah someone needed to charge a smart phone and took it elsewhere
With other people living in the house that think charging their phone is already a big burden I know what will happen when they use the audio devices. They will leave them with depleted batteries for the owner ... All useless irritation...Same with computer audio. I now refuse to listen to computer audio. At first I found it quite comical but it soon started to be annoying. It takes at least an hour fiddling with settings before things are ready. They start changing parameters and drivers etc. and are true masters at the CLI. So at least one hour people fanatically hitting their keyboards, the sound of computer fans and cables and adapters everywhere. For some reason there is always a need to change matters. IMHO it all is a waste of time and a deviation of what this hobby is all about (for me, this is simply a personal item). Of course I am only happy for the people that enjoy such activities.
There still is a market for people that want just to switch on a device and only change source and volume and want simply to enjoy excellent sound quality.
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I have used such modules for cases where galvanic isolation from the mains was needed. But these do not provide high quality, low noise power. Many of them are not regulated at all. So beware when you use them, make sure they fit your needs.
Jan
- Fair enough. But at low power, it's not uncommon to have the xformer onboard even for a linear supply. So it's not that much of a difference. And they really don't take much room onboard. 5x2.5cm for a 10W, 24Vdc supply for example.
- I'd define low power under 10W too.
It's true. The Meanwell IRM-10-24 I'm considering is far from perfect: ±0.3% line regulation, ±0.5% load regulation and up to ±200mV of ripple. But a dumb transformer+diodes+caps supply isn't doing any better, isn't any cheaper (the IRM is 8.3€) and takes more space. In both cases, a sensitive design needs further attention.
Otoh opamps based designs don't need absolutely perfect regulation and noise can/has to be addressed through clc filtering (and rc local filtering).
What ??! For low power in 99% of cases a regulator IC is used. You exaggerate somewhat. I have yet to see a PSU for low power electronics with a classic linear PSU without regulation. Often the electronics are at risk without regulation. As always: the cleaner the PSU the better.
Back to the subject: we apparently need a true audiophile quality mains fed PSU of max. 10VA (adjustable voltage), single or dual output with small dimensions and the possibility to use it either as an adapter in the "wall wart " fashion for those that like that and the possibility to use it directly in a device so mounting holes and pads for an IEC connector. Sturdy PCB design, tested quality and none of the negative things that seem to surround current ready made SMPSes. An SMPS designed for "best of class" performance and not low cost. True harmony with the other audio equipment one has.
Design goals:
- high reliability
- designed for longevity
- fail safe operation
- designed for "always on" operation
- ultra low EMI
- high efficiency
- ultra low ripple
- single or dual output
- configurable from 3.3 to 24V 10VA without compromising on quality, if needed different versions.
- nice load for the grid so no mains pollution
- Use with either plastic wall wart case or integrated in a device
- compact size
Who takes the challenge ?
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NXP seems to produce a number of chips that are ultra low EMI and have some other nice properties. The so-called Greenchip technology. They have types for 10W operation.
http://cache.nxp.com/documents/selection_guide/75016288.pdf
ST makes them also:
http://www.st.com/content/ccc/resou...df/jcr:content/translations/en.DM00096812.pdf
http://cache.nxp.com/documents/selection_guide/75016288.pdf
ST makes them also:
http://www.st.com/content/ccc/resou...df/jcr:content/translations/en.DM00096812.pdf
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I'm not saying linear psu are used without regulation. What I'm saying is that those switcher have to be treated like the first part of a linear supply (the xformer-diodes-caps part).
It'd be quite easy to draw a small pcb with an encapsulated module+lc filter+reg that would achieve your goals.
It seems like that. Real good board layout, meeting design goals and testing will be a real challenge though. If it was that simple most SMPS would be OK but they're not. I already tried it with an LDO in 2014 and made it a Group Buy here. That one is my standard SMPS replacement
http://www.diyaudio.com/forums/group-buys/264185-squeezebox-touch-psu.html Got quite some feedback from builders and most found it to be an improvement over SMPS.I was just thinking of taking this SMPS challenge myself despite my sincere dislike for switchers. Since my experiences with switchers are mediocre at best (in fact I am annoyed right now by one that emits heaps of EMI) why not make a good one ? As far as I can see most chips seem to be optimised for just one output voltage but I will look further. It would hamper a universal design. I don't know if it would be a problem that it is mains connected but if so all the linear PSU's here would be against the rules too. No CE mark and no CE testing are hurdles though (maybe not with DIY....). Builders deviating from the BOM making final results unpredictable so a kit with parts seems the best solution. There are enough reasons against it otherwise we would have seen many GB's here with DIY SMPS
Even the nicest amplifiers seem to have cheap chinese SMPS...
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For example, the meanwell irm serie uses the same package for 5 and 10w modules. You could design a board for that footprint and simply use the best suited module (5, 9, 12, 15, 24v). No dual though.
The best thing about ready made module is that they deal with the dangerous stuff (isolation) and the difficult to get stuff (xformers).
The best thing about ready made module is that they deal with the dangerous stuff (isolation) and the difficult to get stuff (xformers).
Lets take an example:
http://cache.nxp.com/documents/data_sheet/TEA1721AT.pdf?pspll=1
"Fly-back." Needs high coupling between primary to secondary, and generates very high and very fastly changing primary voltage. For this reason Fly-back is the public enemy no1 in terms of EMI. It's simple and cheap, easy to control, but very hard to do with low EMI.
"The burst mode minimizes audible
noise and provides an energy saver state which reduces the power consumption in
no-load condition. The Burst mode frequency of 430 Hz enables no-load power
consumption below < 10 mW at high mains input."
The alarm bell is ringing again. Burst mode is better then squeeking, but definitely not close to audiophile.
"Jitter function for reduced EMI"
This is a trick to spread the EM energy into a wide band, this way the measurement will show many small spectral spikes instead of a few higher. This helps to protect narrow-band receivers, but perfectly useless to avoid direct demodulation within audio devices. And during burst mode the demodulation produces very well audible freq.
Basically no fly-back converters are usable for your stated goal.
LLC topology is the right one for your needs. Maybe 2 transistor forward.
I'm going to further develop my LLC converter to a flawless audiophile PSU, but for power amplifiers.
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Just orientating on the technology, no choices made yet. It seems LLC technology it not available for low power SMPS. I am fully aware I need to know my enemy better
Making this a successful design is impossible with no design experience with SMPS is my second thought. Thirdly I get the impression that designing a low power excellent quality SMPS is harder, less flexible and more expensive than a good LDO design so why bother ? Looking at an amount of audio devices that have been "linearized" I am still convinced these were good decisions. I am reading up and the terms "low cost", "low component count" etc. are frequently used. The technology itself is not designed for quality but for low cost and meeting Energy Star requirements. As always. Down the DC/DC route things look different (small size and very good specs specifically for the megabuck smart phone market) but mains fed low power AC/DC conversion is a low cost area.
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You can use LLC for low power also, just it won't be as cheap and small as a fly-back, and no-load power consumption will also be much higher (for example 400 mW vs. 20 mW). I don't think this would be unacceptable for you.
Well, I need a stand-by PSU, and other housekeeping voltages. Maybe this could be done by a smaller, separate LLC...
If it is done well, then there is much less capacitive coupling from mains side to output, and ripple is also much lower then a transformer+diode+cap PSU, so it has benefits, however needs additional LDOs to reach really low output ripple and impedance. But those LDOs can be set to a real low drop instead of dissipating 40% of the input voltage like in a conventional power supply.
Well, I need a stand-by PSU, and other housekeeping voltages. Maybe this could be done by a smaller, separate LLC...
If it is done well, then there is much less capacitive coupling from mains side to output, and ripple is also much lower then a transformer+diode+cap PSU, so it has benefits, however needs additional LDOs to reach really low output ripple and impedance. But those LDOs can be set to a real low drop instead of dissipating 40% of the input voltage like in a conventional power supply.
Please explain that. It is possible to tune this in a classical transformer-rectifier-capacitor way. The current low noise LDO regs need less than 0.5V drop so with low power supplies things become trivial quite fast
In fact I realise that it makes no sense (IMHO) to design a DIY low power SMPS with the current LDO regs being so good. Most LDO regs have less noise than SMPS as well. It may be otherwise for manufacturers that see their margins drop when using real old fashioned transformers. Please convince me of the necessity of low power SMPS designs that are usable for audio devices that consume less than 10W.The more I think of it: I would even use a low noise LDO 5V "linear" PSU to use with Jan Diddens Silentswitcher.
So, I will always need linear LDO regs to achieve low noise and ripple ?!?!? This proves at least some point
Let's be honest: it has no real benefits trying to design an audiophile approved mains input SMPS for usage under 10VA or 10W. With mains input things become complicated. Today I spent hours reading datasheets of IC's for low power SMPS. Preliminary conclusion: a classical EI or Rcore transformer, rectifier, CLC filtering and LDO are the way to go with low power devices certainly when price-quality (low noise/low EMI/longevity) ratio is concerned. Only when batteries or powerbanks are in the equation, so DC-DC conversion, things are different. Or not ?! I am open to debate, I am not joking. If SMPS is so superior (in practice I only see drawbacks to be honest) then SMPS would be the way to go.It should be clear but again: SMPS for higher power demand is a different subject. I have some 24V 5A SMPS to go with JLH amps. I am not a SMPS hater, I just don't see much positive technical features with SMPS for low power devices. There seems to be a direct connection between copper prices and popularity of low power SMPS
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Jean-Paul,
It depends a lot on where you come from. I provide a couple of SilentSwitchers to a well-known audio designer, also a member here.
Later he showed me his latest phono preamp with a SilentSwitcher build in, he was totally enthusiastic. One point that was important to him: I don't have to worry about mains hum and noise, which always seems to sneak in, even with a linear regulator, no need to put a xformer in a separate box. I just put in a SilentSwitcher and I'm done. Brilliant.
So, as many things in life, it depends.
Jan
It depends a lot on where you come from. I provide a couple of SilentSwitchers to a well-known audio designer, also a member here.
Later he showed me his latest phono preamp with a SilentSwitcher build in, he was totally enthusiastic. One point that was important to him: I don't have to worry about mains hum and noise, which always seems to sneak in, even with a linear regulator, no need to put a xformer in a separate box. I just put in a SilentSwitcher and I'm done. Brilliant.
So, as many things in life, it depends.
Jan
That was already clear to me as I pointed out.
BTW saying a well-known audio designer uses your Silentswitcher is something that your design does not need Jan. For phono preamps extreme details become very important, I never bother too much as I don't experience hum problems with high level 2V output devices like many do. A problem is not a problem when it is unnoticeable. Your Silentswitcher seems absolutely excellent performing. The thought to have 3 clean voltages is an attractive one. As said I was already thinking of trying one out but one worry was gone and then the next came. How am I gonna feed the Silentswitcher ?
For those that don't want yet another battery/powerbank that needs to be charged (BTW where is it, oh my daughter needed to charge her phone) the question arises: A low power SMPS or a linear power supply ? You see ? Like you said, it depends where you come from.
In the line of the original thread subject: are low power SMPS a safe & viable alternative to linear supplies, especially running small (analog) audio units ? You know my answer. Mains fed low power SMPS are no real good alternative for linear PSU's under 10W.
BTW saying a well-known audio designer uses your Silentswitcher is something that your design does not need Jan. For phono preamps extreme details become very important, I never bother too much as I don't experience hum problems with high level 2V output devices like many do. A problem is not a problem when it is unnoticeable. Your Silentswitcher seems absolutely excellent performing. The thought to have 3 clean voltages is an attractive one. As said I was already thinking of trying one out but one worry was gone and then the next came
. How am I gonna feed the Silentswitcher ?For those that don't want yet another battery/powerbank that needs to be charged (BTW where is it, oh my daughter needed to charge her phone) the question arises: A low power SMPS or a linear power supply ? You see ? Like you said, it depends where you come from.
In the line of the original thread subject: are low power SMPS a safe & viable alternative to linear supplies, especially running small (analog) audio units ? You know my answer. Mains fed low power SMPS are no real good alternative for linear PSU's under 10W.
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Please explain that. It is possible to tune this in a classical transformer-rectifier-capacitor way. The current low noise LDO regs need less than 0.5V drop so with low power supplies things become trivial quite fast
A regulated smps provides an output which stays in a 2% range (a typical value), from 100Vac to 250Vac. You can use after it a LDO with an output very close to the nominal output of the smps without fear of dropping out of regulation.
With a linear supply, the variations in the line voltage are directly reflected to the output. You have to design for a worst case scenario. In France (I cannot find the data for Belgium), the mains are allowed to vary from +10% to -15% around 230V. If you design the supply for the -15% scenario, you'll burn a lot of voltage in your regulator in the +10% scenario.
And this is only line regulation. Load regulation is also better with an smps, unless you add a boatload of caps.
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