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UpTone LPS-1 Linear Power Supply Review and Measurements

DonH56

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#61
It is only that easy if you put on those ugly lab coats. :D

Here is the reality of it:

Making low-level measurements is a PITA. A few years ago I was plagued by ~60 kHz switching noise from fluorescent lab lights (the modern little power circuits for them run at that frequency). The SMPS in our boards run up around 500 kHz so that wasn't the problem... And 'scopes, including the slew of $500k models in our test lab, are very susceptible to common-mode noise from the chassis ground. (Note a 'scope, especially a DSO, is generally not a good tool for low-noise measurements.) For low-noise measurements you need to play all sorts of games, from using good (100% foil shield, not braid, or just braid shield) cables, careful grounding (preferably star), excellent shielding (spent a good part of my career in a screen room), DC lighting, etc. etc. etc. In a previous job the screen room was very well isolated to include specially filtered incoming AC mains, DC lights powered by 12 V batteries (chargers off during measurements), and multi-layer screening with additional mu-metal shielding. That small room cost more than many houses. And we still often used small screen boxes for sensitive tests. A screen room does no good if the test equipment is the main noise source...

To put into context:

0 dB = 1 V (for reference)
-60 dB = 1 mV
-80 dB = 100 uV
-100 dB = 10 uV
-120 dB = 1 uV
-140 dB = 100 nV
-160 dB = 10 nV

It does not take much to corrupt even a -120 dB noise floor! I have (rarely) made measurements into the fV range (but would not willingly do it again). I used a leaf electrometer, but an even cooler (no pun intended) version uses a SQUID (superconducting quantum interference device).
 
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amirm

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Thread Starter #62
Except that what you measured was not leakage coming through the output of the LPS-1!

What I am going to show with the following photos and plots is that simply having the Mean Well (or other SMPS) plugged into the wall allows it to radiate (from the brick itself and from the cable) into your single-ended RCA cables from your DAC to the analyzer. As you have pointed out, your analyzer is very sensitive and the harmonics you are picking up are more than 115dBv down.
This is easy enough to test. And test I did :).

1. I measured my iFi iDAC2 first just connected to my laptop without any of your devices on.
2. I then turned on the MeanWell by itself and wrapped its DC cord around the RCA cables as to give it a good shot at doing its radiation thing :).
3. I then turned this up a notch by wrapping the MeanWell DC cord right by the RCA cables connecting to the Audio Precision analyzer.

If your theory is right, the above graphs should be different with #2 and #3 showing the coupling.

4. I then connected the MeanWell supply to UpTone LPS-1, feeding ISO Regen and then iFi iDAC2.

Here are the composite results:

Alex Response_radiated emissions.png


As we see the only scenario showing mains components is when MeanWell is powering the LPS-1/Iso Regen.

The other scenarios with MeanWell power supply being on, having its DC cord literally wrapped around the RCA jacks, etc. generated nothing different than the naked DAC.

Same outlet was used for all of these tests which is a power strip in my rack where the Audio Precision analyzer sits.

So your theory I am afraid is quite wrong. You need to look at your test bench and how you are measuring as you have problems that my setup does not have.
 
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amirm

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Thread Starter #63
And ta-da, a much cleaner plot, proving that what was being measured was NOT leakage coming through the LPS-1's DC output. The active bank (supplying the load) has a pile of opto-isolators (those big white parts across power domain "moats") keeping it isolated from the side that is charging.
I am a bit unclear about your ta-da moment Alex :). You are saying this is with a Linear Power supply and without MeanWell being on, the problem was sorted out.

My issue is that you have your cursor on the second harmonic at 120 Hz. But what about that first peak at mains frequency of 60 Hz? If you have a "moat" between LPS-1 input and output, and user is led to think they are running on independent power from mains, why is that 60 hz component there?

Alex Graph with linear supply.png


Your linear supply is not as clean as my lab one so it is leaking some AC current that is bleeding into the DAC just as my measurements show with other supplies.

Which linear supply did you use anyway? Your own JS-2?

Let me circle back to what you said. What we are dealing with are very small leakages of input to output. All it takes is some small capacitance between input and output and it will leak and show up this way. It doesn't matter how many optoisolators you have. It matters how well you keep this capacitance small.

Anyway, I am pleased to see you investigating DAC outputs now. Hopefully the main cause can be found and fixed in LPS-1.
 

Superdad

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#64
Something is fishy there, but without seeing your set up we can not know what.

Guess you'll have to wait until we publish direct leakage current graphs from the output of several supplies--including the LPS-1. There is no 60/120/180Hz noise on the output an LPS-1. Zero, zip, nada. It's like a battery. A tiny bit of capacitive coupling of the transistors we use will let some through in the MHz range, but SMPS units are required to not have any leakage up in that range.

Enjoy the eclipse. Stay home and avoid the traffic.
--Alex C.
 
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amirm

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Thread Starter #65
Now like the DACs you used, the Micca OriGen+ was pretty sensitive to the radiated harmonics of the Mean Well and other SMPS charging units (you already saw the even worse iFi iPower). But every DAC is different--likely owing to its output impedance and the analog cables used. So here is the same set up, with the Mean Well powering the LPS-1, but with an HRT MusicStreamer DAC:
On this one, I think confusion is created by the higher noise floor of the HRT MusicStreamer. Here is its response overlaid on top of the Origen DAC you reported on with linear supply with the HRT graph in purple now:

Alex Graph with linear supply Music Streamer.png


On second harmonic where you have your cursor (X), it is just buried in the noise of the DAC. The mains contribution at 60 Hz however is visible still. Its level is diminished some to be sure, but it is still there showing once more that AC mains is leaking onto its output.
 

March Audio

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#66
Right, so let me be sure I understand correctly. According to Alex the mean well is radiating mains and harmonics. So much so it is picked up through the dac casing and output lead.

However even though the lps1 is directly connected to the mean well, it somehow remains impervious to this radiated problem.

.......hmmmm........let me see.........

Also, in terms of radiated problems I wouldn't expect the mean well to have significant problems at line frequency, I would expect the major problem to be at it's,switching frequency and harmonics.
 
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amirm

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Thread Starter #67
Question about your setup Alex:



I see that the Iso Regen is outside of its enclosure. Did you do all of your testing with it exposed? If not, what do the measurements look like with it in its metal box?

Also, you have those cables all looped up. What happens if you run them straight?
 

Jinjuku

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#68
This is easy enough to test. And test I did :).

1. I measured my iFi iDAC2 first just connected to my laptop without any of your devices on.
2. I then turned on the MeanWell by itself and wrapped its DC cord around the RCA cables as to give it a good shot at doing its radiation thing :).
3. I then turned this up a notch by wrapping the MeanWell DC cord right by the RCA cables connecting to the Audio Precision analyzer.

If your theory is right, the above graphs should be different with #2 and #3 showing the coupling.

4. I then connected the MeanWell supply to UpTone LPS-1, feeding ISO Regen and then iFi iDAC2.

Here are the composite results:

View attachment 8242

As we see the only scenario showing mains components is when MeanWell is powering the LPS-1/Iso Regen.

The other scenarios with MeanWell power supply being on, having its DC cord literally wrapped around the RCA jacks, etc. generated nothing different than the naked DAC.

Same outlet was used for all of these tests which is a power strip in my rack where the Audio Precision analyzer sits.

So your theory I am afraid is quite wrong. You need to look at your test bench and how you are measuring as you have problems that my setup does not have.
Did you have a load on the MeanWell when doing this?
 
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amirm

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Thread Starter #69
Did you have a load on the MeanWell when doing this?
I did in the case of the Gray curve. In that scenario, iFi was plugged into computer USB while the MeanWell was powering the LPS-1 and ISO Regen. No mains components were visible.

For completeness, I just repeated the test, this time putting on a dummy load of about 10 ohms on the MeanWell Supply. Two runs:

Yellow) DAC connected directly to computer over USB *and* MeanWell Supply powered on near it and connected to 10 ohm load
Red) DAC connected through LPS-1/ISO Regen being powered by MeanWell Supply
upload_2017-8-19_22-6-10.png


As you see, the comparison does not change. The peaks are only highly visible when the LPS-1, ISO-Regen and MeanWell are powering the DAC.

Mere fact of having the MeanWell supply on with or without load makes no difference in my measurements.

As I said, this is a measurement error in Alex/John's setup. At the low levels we are measuring, it is very easy to have mains leakage creep into instrumentation.
 
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amirm

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Thread Starter #70
So I had a thought to measure one more thing. Remembering that the LPS-1 can power Iso Regen and my DAC for about two seconds, I put the Audio Precision Analyzer in fast mode (i.e. no averaging) and made one measurement with MeanWell powering everything, and another, with power disconnected from LPS-1:

LPS1 with and without power.png


As always, we see that when the power is connected (in red), we see our usual mains spikes (60 and 180 hz above).

But the moment I disconnect the power, while everything including position of the MeanWell power supply is the same and its DC wire, the mains contributions vanish (yellow).

Clearly then the conduction path is through the DC cable of Meanwell to LPS1, to ISO Regen and eventually to the DAC and my analyzer.

If anything was "radiated" then the two graphs should have been the same. They are not.

In summary, LPS-1 is a floating supply only in the case that it truly is: in the two seconds when nothing powers it! :) The moment you connect it to a supply source, all bets are off.
 
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amirm

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Thread Starter #71
So to summarize:

1. Alex/John's own graphs and measurements show mains contributions at 60 Hz in all scenarios including his linear power supply. In that sense, they are very much in agreement with my findings.

2. Their instrumentation is sensitive to coupling from the MeanWell supply. That makes them ill-suited to this type of measurements. It is not easy to dig so deep into response of a DAC. Proper equipment/protocol needs to be used.

3. Mimicking similar configurations to theirs (and then some), my setup shows no such vulnerability. I cannot, no matter which way I have tried, to induce mains contributions externally to the measurement loop.

4. My last test clearly shows that AC leakage is travelling through the DC cable of MeanWell supply to the LPS-1 and then downstream. As such, the LPS-1 is not providing isolation to mains leakage as advertised.

I would appreciate Alex's confirmation or data and explanation to the contrary. Otherwise, my original data and conclusions very much hold.
 

RayDunzl

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#72
 

Sal1950

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#73

Wiebren

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#74
In another thread, Thomas asked me for a recommendation on a good linear Power supply. As it happens, I have a linear power supply that is designed to actually better the performance of UpTone among others! It is from the Dutch company Sbooster and the specific product is "BOTW" https://www.sbooster.com/botw-pp-eco/

Here is a comparison of iFi iDAC2 DAC, being driven by ISO Regen and LPS-1 with power coming from my lab linear power supply and Sbooster BOTW:

View attachment 8173

As we see they are comparable and there is no extra mains contribution as there is with MeanWell power supply feeding the LPS-1.

I have met the company principals, Wiebren Draaijer, and Karin Hoks and they are delightful people. So happy to send them business (no affiliation) should you need a supply like this.
Amir,

Thank you for the measurement, recommendation and kind words. It was our pleasure to have met you in person at last CES.

Although it is not a key-feature of our power supplies, we are happy to see that your test-results confirm the negligible AC-leakage of our BOTW P&P ECO power supply.

Great to see that the new forum is growing so fast with a lot of interesting technic topics also for us as manufacturer. We are looking forward to your next “proof of a claim”. ;)

Karin & Wiebren
 

jtwrace

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#75
Amir,

Thank you for the measurement, recommendation and kind words. It was our pleasure to have met you in person at last CES.

Although it is not a key-feature of our power supplies, we are happy to see that your test-results confirm the negligible AC-leakage of our BOTW P&P ECO power supply.

Great to see that the new forum is growing so fast with a lot of interesting technic topics also for us as manufacturer. We are looking forward to your next “proof of a claim”. ;)

Karin & Wiebren
I presume that you're with SBooster? You should offer ASR members a discount. :p
 

watchnerd

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#76
The logic of the product totally eludes me. Why would you spend $400 on a psu that (allegedly) improves your inadequate dac. Sell your inadequate DAC, add the $400 and buy a decent DAC!
And then after that, sell your decent DAC for an active speaker with digital inputs and stop worrying about this nonsense entirely.
 

Jinjuku

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#77
And then after that, sell your decent DAC for an active speaker with digital inputs and stop worrying about this nonsense entirely.
That only works if there is a speaker you want available that way.
 

watchnerd

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#78
That only works if there is a speaker you want available that way.
There are several, in my case. KEF LS50 Wireless, JBL 705P/708P, Dynaudio XD series, Genelec, Vanatoo

And for the masses, even more -- Sonos, Amazon Echo, Apple Homepod, every Bluetooth portable speaker on the planet...
 
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#79
It is only that easy if you put on those ugly lab coats. :D

Here is the reality of it:

Hi guys, This is one of my absolute favorite videos of all time. Really strong work.

May I suggest that "leakage" be reserved for the known use of "leakage current" (which very well might be at play given SMPS etc) and that PSRR better term to describe generalize appearance of mains 50/60/70 whatever on output?
 
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