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Low cost high quality excellent performing LPSU for audio.


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Is there such a thing?

 

I truly believe that removing a standard SMPS is the way to go - in my own system it's very obvious listening to the benefit of using Auralic's own LPSU on an Auralic Mini for example. I use the spdif from the Mini into a Metrum Octave v2 DAC - the Metrum is super sensitive to upstream changes - the better the feed the better the sound (bad feeds result in a mushy flat sound in comparison) - so the Metrum is the perfect Canary in the Mine for testing these things out.

 

Some of these 'audiophile' LPSU's are so expensive though. 

 

I'm now on the hunt for an affordable yet no compromise (hopefully this isn't an oxymoron) 5V LPSU.

 

Will something like this: https://www.ebay.co.uk/itm/LKS-Linear-power-supply-DC-5V-USB-5V-for-DAC-with-25VA-Talema-transformer-PSU-/272884127978

 

... be good enough? Not just to improve upon an SMPS - but to 'significantly' improve upon a SMPS! I see in audio circles that you can spend a ridiculous amount of money on some PSU's for audio systems - and I do recognise the fact that a quality PSU does make a positive difference.  But I'm looking for another less marketed solution that will be equally as good as well reviewed and well known alternatives if possible like in the example link above.

 

 

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31 minutes ago, seeteeyou said:

Thanks - it's good to have experience and feedback on makes such as this proving themselves to be a good alternative to far more expensive units.

 

A battery powerbank used to charge your phone was another idea - but I read that the regulators in these powerbanks are 'noisy' so do not serve audio as well as we would like them too. Shame really - because 5V is the usual voltage from a powerbank. Unless anyone out there knows of a powerbank that works well and 'sounds good'.

 

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17 minutes ago, Kal Rubinson said:

But not an LPSU?  Manual says "Adaptor is a kind of external switching power supply....."

 

Yeah, it is SMPS. Why would it need to be LPSU?

 

Thing is that you don't need to have 50/60 Hz transformer to have good PSU. Or even LPSU. You can also have LPSU with transformers running for example at 50/60 kHz instead. Most would call latter one "SMPS" and first one "LPSU". But it is not that black and white.

 

Signalyst - Developer of HQPlayer

Pulse & Fidelity - Software Defined Amplifiers

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Here's a good table that explains the differences between SMPS and Linear (regulated) Power Supplies. The rest of the texts comes from Acopian (not my words!). For audio use it's clear to use a linear power supply over an SMPS. The EMI at 60 kHz to 200 kHz is not acceptable, being responsible for high leakage currents from an SMPS which screw up DAC imaging plus a host of other reprehensible artifacts. It is that black and white.

 

image.thumb.png.1249eb082641d9895323773b84ea62cf.png

 

Application guides

 

A linear regulated power supply regulates the output voltage by dropping excess voltage in a series dissipative component. 
They use a moderately complex regulator circuit to achieve very low load and line regulation. 
Linear regulated power supplies also have very little ripple and very little output noise.


General purpose use - including, but not limited to:

  • low noise amplifiers
  • signal processing
  • data acquisition - including sensors, multiplexers, A/D converters, and sample & hold circuits.
  • automatic test equipment
  • laboratory test equipment
  • control circuits
  • anywhere that excellent regulation and/or low ripple is required

Noise (from page 6 of the pdf attached to this post) 


The linear supply is a continuous function unit with no discrete time clocking
or switching action. As a result, the output is virtually noise and ripple free,
and any noise seen at the load is due to pickup outside the supply itself in
the power wiring between supply and load.
Using chokes and other filter
components as well as careful routing of the output cabling can attenuate
this noise. The linear supply itself does not generate any EMI or RFI.
In contrast, the switching supply is inherently a source of noise, with a
fundamental at its clock frequency as well as numerous harmonics. Typical
noise levels are on the order of hundreds of microvolts to tens of millivolts.
This is unacceptable for many applications where the output voltage is at
single-digit levels, or the load is sensitive to supply rail noise.


This switching-based noise can be filtered to some extent but is very difficult
to eliminate entirely. In addition to noise on the output cables, there is also
noise radiated by the supply, which can induce unexpected and frustrating
problems elsewhere in the system. Further, while filtering can attenuate the
output noise to an acceptable level, the problem of radiated noise is much
more difficult to manage.


Further, the frequency of the switching-induced noise may interfere with
other clocked signals, resulting in beat frequencies and other interfering
signals. In some cases, the switching supply’s clock frequency must by
synchronized with the system clock.


Further aggravating the situation, there are increasingly stringent
regulatory limits on how much noise a power supply can generate in
different frequency bands, both as a function of power supply wattage
and global zone. Some switching supplies meet the regulatory mandates
by using spread spectrum clocking, which spreads the noise energy across
a wide band. By doing so, the noise does not exceed allowed limits at
the clock frequency or its harmonics. While this technique works in the
“legal” sense to meet mandatory standards, the supply noise can still affect
internal system circuitry..

 

 

 

Linear-Vs-Switching-Power-Supplies-Whitepaper.pdf

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17 hours ago, Miska said:

Yeah, it is SMPS. Why would it need to be LPSU?

I am not disputing the specifics of this unit or its suitability but pointing out that LPSU is the title/topic of the thread. 🙃

 

Kal Rubinson

Senior Contributing Editor, Stereophile

 

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17 hours ago, Miska said:

Thing is that you don't need to have 50/60 Hz transformer to have good PSU. Or even LPSU. You can also have LPSU with transformers running for example at 50/60 kHz instead. Most would call latter one "SMPS" and first one "LPSU". But it is not that black and white.

 

 

Absolutely, the "hybrid" model of SMPS to act as a pre-regulator followed by a low drop out linear as Analog Devices discusses in the use of its LT3045 https://www.analog.com/en/technical-articles/low-noise-power-supplies-come-in-many-flavors-part-1-linear-regulators.html

 

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12 hours ago, One and a half said:

For audio use it's clear to use a linear power supply over an SMPS. The EMI at 60 kHz to 200 kHz is not acceptable, being responsible for high leakage currents from an SMPS which screw up DAC imaging plus a host of other reprehensible artifacts. It is that black and white.

 

 

Its never that black and white. There are most certainly very high quality SMPS which have very low common mode noise aka "leakage currents" ... of course these circuits might have on board or on chip linear regulators. An example would be a 100Gbe NIC that works in a bog standard PC with a noisy power supply. The NIC of course has its own onboard power supply that filters the junk away ... otherwise it just doesn't work!!!

 

*** for some reason this is posted in the networking section so I am assuming power supplies for high quality network gear must be the interest???

 

Moreover crappy 60Hz AC transformers can pump all sorts of leakage currents into a "linear" supply.

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YGWYPF.  Teradaks will give you an inkling of what an LPS can do. If you want cost efficiency, an HDPlex 300W is a good starting point because you

can power 4 devices with differing voltages. But once you get on that bus and see results, its going to motivate you to obtain better 🤑

Regards,

Dave

 

Audio system

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21 hours ago, One and a half said:

For audio use it's clear to use a linear power supply over an SMPS. The EMI at 60 kHz to 200 kHz is not acceptable, being responsible for high leakage currents from an SMPS which screw up DAC imaging plus a host of other reprehensible artifacts. It is that black and white.

 

It is not so clear.

 

Medical grade PSUs, like the one I referred to, have been specifically designed to have very low leakage currents, in µA range.

 

Even with standard SMPS wall-warts, it is entirely possible to design very low noise analog devices. I have measured enough many DACs running from SMPS that I know it is more about the design than the type of PSU. Overall, 60/200 kHz is much easier to filter out than 50/60/100/120 Hz. Especially since the fundamental and it's harmonics are outside of audio band.

 

Signalyst - Developer of HQPlayer

Pulse & Fidelity - Software Defined Amplifiers

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OK so a good quality SMPS is as good as a good quality LPSU.

 

I just looked on Mojo Audios website and this is his take on an SMPS power supply:

 

https://www.mojo-audio.com/power-supply-faqs/

The disadvantages of SMPS is they have significantly more noise than linear power supplies. The best SMPS have peak-to-peak ripple (noise) roughly equal to the most basic of linear power supplies. But ripple is not the only noise SMPS produce. They also radiate inductive noise that can be picked up by cables and components in close proximity. And they dump noise onto the common AC ground that pollutes the power of any component plugged into the same AC circuit.

Also, when compared to high-performance linear power supplies, SMPS have very slow dynamic response. When reproducing music, slower power supplies sound awkward and less liquid, restrict dynamic passages, mask micro-details and micro-dynamics, and distort the time and tune.

 

 

 

 

 

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On 1/10/2021 at 10:59 AM, Miska said:

 

It is not so clear.

 

Medical grade PSUs, like the one I referred to, have been specifically designed to have very low leakage currents, in µA range.

 

Even with standard SMPS wall-warts, it is entirely possible to design very low noise analog devices. I have measured enough many DACs running from SMPS that I know it is more about the design than the type of PSU. Overall, 60/200 kHz is much easier to filter out than 50/60/100/120 Hz. Especially since the fundamental and it's harmonics are outside of audio band.

 

Well, the measurements for so called low leakage supplies are usually in isolation, like the ifi iPower fabrications. Once they are connected to a load and actually supply voltage, the crap and mire they generate is audible soon enough.

 

On the subject of iPower. For a resurrection of the iTbube2 for tuner use, while on the bench was a good time to measure the iPower.

 

Rated at 15V, the output was 15.23 V DC. For a line voltage of 115V AC, the 0V output measured to the Active or Neutral was 52V AC. To kill this voltage, the output 0V needs grounding (to hard earth) and the easiest path to do this is via the iTube2 RCA outer shell cases which are dead short to the 0V output. So the signal leads carry 52V of leakage back to the amplifier. Eeuuw.

 

For those interested in following this thread, the values of AC volts between frames of connected devices, ideally is 0 V. This means no leakage currents can develop between devices, such as a DAC and amplifier. No leakage currents is a cleaner signal, not added with bonus noise.

 

In the chain measured just now in the (non-critical) office setup with a Fluke 289:

 

Accuphase E-450 Integrated amplifier frame -> Grace Design m930 DAC frame, connected via RCA, the potential reads 0.08V AC, could be better, but that's what it is with standard unshielded AC cables and not very studious where they are routed. With the iPower connected to the iTube 2 the same measurement points  rise to 0.32 V AC. Now the itube 2 also needs a DC-DC converter to raise the tube's requirement B+ to 50V something +. Hey, there's another SMPS, they're everywhere. Low noise, hahahaha, not. 

 

 

 

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9 minutes ago, airguitar said:

Thanks for that link.

 

Interesting the reference to batteries and noisy regulators. But at least the battery cannot inject noise into other equipment because it is not directly connected to the mains.

And a battery is incapable of generating RF and EMI. Depending on its size, it can run out of puff for dynamic swinging loads that are repetitive. 

 

99.3% (my guess) of noise from linear supplies are as a direct result of connected to an AC network with:

a) noisy SMPS close to the audio equipment

b) large switching AC devices, heaters, air con and faulty fridge starters

c) wearing out light switch contacts 

d) less optimum earthing (grounding)

e) incorrectly designed audio equipment to begin with (look at a few Pro audio devices XLR wiring)

f) fluorescent lamps

g) Energy saving = bulk harmonics generator light globes (each one has an SMPS)

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1 hour ago, One and a half said:

And a battery is incapable of generating RF and EMI. Depending on its size, it can run out of puff for dynamic swinging loads that are repetitive. 

 

99.3% (my guess) of noise from linear supplies are as a direct result of connected to an AC network with:

a) noisy SMPS close to the audio equipment

b) large switching AC devices, heaters, air con and faulty fridge starters

c) wearing out light switch contacts 

d) less optimum earthing (grounding)

e) incorrectly designed audio equipment to begin with (look at a few Pro audio devices XLR wiring)

f) fluorescent lamps

g) Energy saving = bulk harmonics generator light globes (each one has an SMPS)

 

There's no avoiding this noisy crap in the house! Perhaps one of those fancy extension blocks that filter out the rubbish created from all over the house is a better plan.

 

Sometimes I think it's a lot easier finding an all in one solution which has amplification - good power supplies - and streaming services built in to avoid multiple mains connections - thus avoiding the risk of ground loops - and avoiding the need to consider each separate components power supply quality - make it one connection and be done with it!

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21 hours ago, One and a half said:

And a battery is incapable of generating RF and EMI. Depending on its size, it can run out of puff for dynamic swinging loads that are repetitive. 

 

 

Just thinking about the dynamic swing load statement - if I am simply using a solid state streaming bridge like a Primare NP5 which just takes 5V (ideal for a phone powerbank charger) - where do dynamic swings come into play here? I mean it's just a circuit decoding digital and surely it's the pre-amp or power amps job to deal with dynamic swings where the signal is analog?

 

 

 

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On 1/12/2021 at 6:24 PM, airguitar said:

Just thinking about the dynamic swing load statement - if I am simply using a solid state streaming bridge like a Primare NP5 which just takes 5V (ideal for a phone powerbank charger) - where do dynamic swings come into play here? I mean it's just a circuit decoding digital and surely it's the pre-amp or power amps job to deal with dynamic swings where the signal is analog?

Oh, when digital circuits work, they don't 'pull' current in a fixed linear smooth load. They pull currents that are pulses and vary with activity, hence why I referred to them as dynamic. Paul Hynes makes mention of this, so does Acopian, the power supply needs to cope with this kind of load, that's their recovery specifications. An SMPS unless it's oversized has some difficulty in keeping up, but then we suffer the noise problem anyway.

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On 1/15/2021 at 1:31 AM, ChrisG said:

have a couple of Farad Super3s

I had the ZeroZone LEO LPS 19v version and the Super3 19v.  The Super3 wasn't much better in reality than the LEO LPS.  So there are definitely some (relative) bargains to be had, but its difficult to spot them in the wilderness.

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On 1/10/2021 at 12:59 AM, Miska said:

Medical grade PSUs, like the one I referred to, have been specifically designed to have very low leakage currents, in µA range.

 

The off-the-shelf medical grade PSUs  whilst have low leakage current, still can't compete subjectively with an OK grade linear PSU in practice.  

 

On 1/10/2021 at 12:59 AM, Miska said:

Even with standard SMPS wall-warts, it is entirely possible to design very low noise analog devices. I have measured enough many DACs running from SMPS that I know it is more about the design than the type of PSU. Overall, 60/200 kHz is much easier to filter out than 50/60/100/120 Hz. Especially since the fundamental and it's harmonics are outside of audio band.

 

Hopefully Taiko Audio's switching DC-DC converter will start to put an end to the snobbery that prevents HQ SMPS (of low leakage) being developed for this application.  They too have designed their DC-DC switching frequency well out of the way of typical audio bands.

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