pinkupanda
Member
- Joined
- Aug 5, 2017
- Messages
- 59
- Likes
- 20
Thanks to sites like ASR, I would say awareness is a good thing which is hard to comeby for most audiophools 
-
WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!
UpTone LPS-1 Linear Power Supply Review and Measurements
- Thread starter amirm
- Start date
Mivera
Major Contributor
There is RMS and P-P ripple noise. There is leakage current. EMI etc. All of the specs in the PDF's I shared are industry standard tests for power supply performance. They are nothing proprietary to Daitron.
Mivera
Major Contributor
Great video here on how to properly test power supplies for ripple noise:
Last edited:
OP
- Thread Starter
- #44
OP
- Thread Starter
- #46
Buy it and then loan it to me to measure.
Mivera
Major Contributor
It is only that easy if you put on those ugly lab coats.
Here is the reality of it:
With that accent of his no wonder it took him so long to find the source of the noise!
Mivera
Major Contributor
Considering the leakage current blockage aspect of the LPS-1 has been debunked, here's a regulator board that's likely better engineered that uses the same regulators.
http://m.ebay.com/itm/TPS7A4700-TPS...3D252501322400&_trksid=p2056116.c100408.m2460
Adjustable to several voltages with solder jumpers. He provides the full gamut of measured results as well. Pretty much built to the exact TI reference design.
http://m.ebay.com/itm/TPS7A4700-TPS...3D252501322400&_trksid=p2056116.c100408.m2460
Adjustable to several voltages with solder jumpers. He provides the full gamut of measured results as well. Pretty much built to the exact TI reference design.
Mivera
Major Contributor
Just found the same guy has LT3045 based reg boards now. Lowest noise 500mA reg on the planet. PSRR is phenomenal as well. Run a cheap SMPS through this board and it would blow away the LPS-1 for only $22.
http://m.ebay.com/itm/LT3045-S-Ultralow-noise-0-8-Vrms-LDO-linear-regulator-0V-15V-500mA-Fixed-out-/252951737282?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20150519202348%26meid%3D926fed1b86a0442785e7f06c458883d6%26pid%3D100408%26rk%3D1%26rkt%3D25%26sd%3D252996183940&_trksid=p2056116.c100408.m2460
For drop in replacement upgrade of TO-220 style reg's he made these:
http://m.ebay.com/itm/LT3045-78xx-Ultralow-noise-0-8-Vrms-linear-regulator-0V-15V-0-5A-78xx-Layout-/252948166542?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20150519202348%26meid%3Ded26133e3a034327945a85ab33551148%26pid%3D100408%26rk%3D1%26rkt%3D25%26sd%3D252951737282&_trksid=p2056116.c100408.m2460
Amir should order some and directly compare to the LPS-1 connected to ISO-regen/Schitt DAC. Very simple to hook up. Just snip the DC cable of the Meanwell supply and solder it inline.
http://m.ebay.com/itm/LT3045-S-Ultralow-noise-0-8-Vrms-LDO-linear-regulator-0V-15V-500mA-Fixed-out-/252951737282?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20150519202348%26meid%3D926fed1b86a0442785e7f06c458883d6%26pid%3D100408%26rk%3D1%26rkt%3D25%26sd%3D252996183940&_trksid=p2056116.c100408.m2460
For drop in replacement upgrade of TO-220 style reg's he made these:
http://m.ebay.com/itm/LT3045-78xx-Ultralow-noise-0-8-Vrms-linear-regulator-0V-15V-0-5A-78xx-Layout-/252948166542?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20150519202348%26meid%3Ded26133e3a034327945a85ab33551148%26pid%3D100408%26rk%3D1%26rkt%3D25%26sd%3D252951737282&_trksid=p2056116.c100408.m2460
Amir should order some and directly compare to the LPS-1 connected to ISO-regen/Schitt DAC. Very simple to hook up. Just snip the DC cable of the Meanwell supply and solder it inline.
Last edited:
OP
- Thread Starter
- #51
OK, here is a mini teardown of the UpTone LPS-1.
The enclosure is similar to a number of their other products: anodized aluminum in which a PC board slides in with two end caps. Self-tapping screws are used to hold the end panels which is a cheap way out but acceptable given the fact that you won't be opening and closing it often.
The box is larger than their other products which makes it much less cheap looking. And it also has four stick on feet which combined with its increased weight allows it to mostly sit put and not have it be dragged by its wires.
Once inside, you are greeted with the top side of the board which has the dual bank of supercapacitors from Maxwell Technologies: http://www.maxwell.com/images/documents/hcseries_ds_1013793-9.pdf
The capacitors have been bent 90 degrees to allow them to lay down -- downside of using too small of an enclosure. Fortunately they are glued down with the white sticky silicone or whatever they have used.
Supercapacitors for those of you who don't know, are very large capacitors and are able to be charged to hold fair amount of energy (although a fraction of a battery). Importantly they can be charged much, much faster than a battery. Here, they hold enough energy to power the device for a few seconds after which, the output is switched to the other bank which has been charged in advance (there is a long, minute or so when you power on the unit until it has charged both banks).
The capacitor ratings is 85 degree C which would be fine if it is not close to heat generating sources. My preference is to see 105 degree C caps in power supplies but I don't know if Maxwell caps come in that temperature grade.
There is an LED indicator that tells you when the banks are ready for use (it turns green).
The "business end" is on the bottom side:
Wow, this is quite sophisticated! Hell of alot of parts in there. The heart of which is the Altera FPGA. This is a programmable logic device which includes memory. two analog to digital converters and a microprocessor. FPGAs are normally used when CPUs are not fast enough to do the job in software. I don't know of any design characteristics of this type of device as to require an FPGA. I am at a loss as to why this part is used other than maybe more familiarity of the designer with hardware than software. Or a way of making the design difficult to copy.
Even outside of the FPGA, there is a ton more complexity and parts. I have not tried to reverse engineer any of it. Just glancing, we see a large number of power products, regulators/power switches, anywhere you see that copper surface. These parts generate heat and their way of dissipating that is through the copper PCB. Unfortunately those super capacitors sit right on top of them, absorbing some of that heat. I have not made any measurements but in just feeling the unit, it does not get hot enough to make me be concerned about short life. It is just that all else being equal, I would have wanted to see the supercap bank and power devices separated than sitting on two sides of the PCB.
The assembly of the parts is first class. I see no hacks, wires, bad solder joints, etc. This is a sign of a good design and good contract manufacturer.
If there is interest I can dig into it more but for now, I give the overall design and engineering a thumbs up! Definitely huge step up from any DIY effort.
Had this board been put in a larger box, with a linear power supply, it would have been golden as far as its design targets.
The enclosure is similar to a number of their other products: anodized aluminum in which a PC board slides in with two end caps. Self-tapping screws are used to hold the end panels which is a cheap way out but acceptable given the fact that you won't be opening and closing it often.
The box is larger than their other products which makes it much less cheap looking. And it also has four stick on feet which combined with its increased weight allows it to mostly sit put and not have it be dragged by its wires.
Once inside, you are greeted with the top side of the board which has the dual bank of supercapacitors from Maxwell Technologies: http://www.maxwell.com/images/documents/hcseries_ds_1013793-9.pdf
The capacitors have been bent 90 degrees to allow them to lay down -- downside of using too small of an enclosure. Fortunately they are glued down with the white sticky silicone or whatever they have used.
Supercapacitors for those of you who don't know, are very large capacitors and are able to be charged to hold fair amount of energy (although a fraction of a battery). Importantly they can be charged much, much faster than a battery. Here, they hold enough energy to power the device for a few seconds after which, the output is switched to the other bank which has been charged in advance (there is a long, minute or so when you power on the unit until it has charged both banks).
The capacitor ratings is 85 degree C which would be fine if it is not close to heat generating sources. My preference is to see 105 degree C caps in power supplies but I don't know if Maxwell caps come in that temperature grade.
There is an LED indicator that tells you when the banks are ready for use (it turns green).
The "business end" is on the bottom side:
Wow, this is quite sophisticated! Hell of alot of parts in there. The heart of which is the Altera FPGA. This is a programmable logic device which includes memory. two analog to digital converters and a microprocessor. FPGAs are normally used when CPUs are not fast enough to do the job in software. I don't know of any design characteristics of this type of device as to require an FPGA. I am at a loss as to why this part is used other than maybe more familiarity of the designer with hardware than software. Or a way of making the design difficult to copy.
Even outside of the FPGA, there is a ton more complexity and parts. I have not tried to reverse engineer any of it. Just glancing, we see a large number of power products, regulators/power switches, anywhere you see that copper surface. These parts generate heat and their way of dissipating that is through the copper PCB. Unfortunately those super capacitors sit right on top of them, absorbing some of that heat. I have not made any measurements but in just feeling the unit, it does not get hot enough to make me be concerned about short life. It is just that all else being equal, I would have wanted to see the supercap bank and power devices separated than sitting on two sides of the PCB.
The assembly of the parts is first class. I see no hacks, wires, bad solder joints, etc. This is a sign of a good design and good contract manufacturer.
If there is interest I can dig into it more but for now, I give the overall design and engineering a thumbs up! Definitely huge step up from any DIY effort.
Had this board been put in a larger box, with a linear power supply, it would have been golden as far as its design targets.
What a massively complex load of nonsense!
Even if, in isolation, it provides a fractionally quieter output than a well designed "traditional" supply, where is the evidence that this is beneficial to any way to any end product?
Even if, in isolation, it provides a fractionally quieter output than a well designed "traditional" supply, where is the evidence that this is beneficial to any way to any end product?
Mivera
Major Contributor
What's more important, complexity, or performance?
So now your looking for evidence, how rude.
OP
- Thread Starter
- #56
Look forward to it. His job is to figure out what it is. Mine is to report that whatever it is, shows up on the output of the DAC. And it changes with every power supply I use to feed the LPS-1 (hence it is sensitive to what powers it).
OP
- Thread Starter
- #57
So here is some preliminary data to chew on.
Up to now, I have been measuring how the output of DACs change with all of these tweak products upstream.
I thought I fire up my Tektronix scope and see what it shows in time domain. Capture method is through my differential probe+amplifier. Do not even attempt to make these measurements with regular scope probes.
To help make things better for the product, I set the bandwidth of the scope to 20 Mhz which is sort of an industry standard (scope bandwidth otherwise is 500 Mhz)
I powered the UpTone LPS-1 with the Meanwell Power supply and noticed it very interesting behavior. As it sits there, the level of noise it produces is smoothly (more or less) is changing. I should shoot a video of it but for now, these are three snapshots of it:
Notice the oval shape which indicates low frequency noise (mains?) riding on top of the high frequency ones.
This "breathing"/cycling continues all the time. To capture them all, I set the scope to envelop mode and after a few seconds, this is what I get:
Notice the distinct notches in the response indicating deterministic components.
I then changed the supply to my lab linear power supply. This time the breathing stopped:
Going into envelop mode, we get this for composite noise profile of the Linear Power Supply:
Notice how regular and smooth the response is now with the linear supply, indicating no deterministic components. From psychoacoustics point of view, you want to get random noise as that is far less of an audible concern than deterministic frequencies/tones.
In summary:
1. If you think the UpTonoe LPS-1's output is independent of input, think again. Clearly its output is impacted by what you feed it. And the recommended MeanWell switchmode power supply contributes fair amount of junk to the output.
2. The constant breathing should be very upsetting to folks who go to great lengths to elevate cables, get rid of noise, etc. By inserting this device in the path, you have created a problem that normally would cause you to lose sleep.
Again, this is work in progress and as always, comments, corrections, feedback, etc. is appreciated.
Up to now, I have been measuring how the output of DACs change with all of these tweak products upstream.
I thought I fire up my Tektronix scope and see what it shows in time domain. Capture method is through my differential probe+amplifier. Do not even attempt to make these measurements with regular scope probes.
To help make things better for the product, I set the bandwidth of the scope to 20 Mhz which is sort of an industry standard (scope bandwidth otherwise is 500 Mhz)
I powered the UpTone LPS-1 with the Meanwell Power supply and noticed it very interesting behavior. As it sits there, the level of noise it produces is smoothly (more or less) is changing. I should shoot a video of it but for now, these are three snapshots of it:
Notice the oval shape which indicates low frequency noise (mains?) riding on top of the high frequency ones.
This "breathing"/cycling continues all the time. To capture them all, I set the scope to envelop mode and after a few seconds, this is what I get:
Notice the distinct notches in the response indicating deterministic components.
I then changed the supply to my lab linear power supply. This time the breathing stopped:
Going into envelop mode, we get this for composite noise profile of the Linear Power Supply:
Notice how regular and smooth the response is now with the linear supply, indicating no deterministic components. From psychoacoustics point of view, you want to get random noise as that is far less of an audible concern than deterministic frequencies/tones.
In summary:
1. If you think the UpTonoe LPS-1's output is independent of input, think again. Clearly its output is impacted by what you feed it. And the recommended MeanWell switchmode power supply contributes fair amount of junk to the output.
2. The constant breathing should be very upsetting to folks who go to great lengths to elevate cables, get rid of noise, etc. By inserting this device in the path, you have created a problem that normally would cause you to lose sleep
.Again, this is work in progress and as always, comments, corrections, feedback, etc. is appreciated.
OP
- Thread Starter
- #58
And oh this is the output of the Meanwell Power Supply by itself:
And again what happens to it when it is gone through LPS-1:
Notice how the LPS-1 is passing through some of what MeanWell supply created and its own noise overlaid on top of it.
And again what happens to it when it is gone through LPS-1:
Notice how the LPS-1 is passing through some of what MeanWell supply created and its own noise overlaid on top of it.
- Joined
- Aug 6, 2017
- Messages
- 149
- Likes
- 91
Hello again gang:
It has been a busy week, and since I don't generally hang out with the friendly, pitchfork wielding crowd here, I was not aware of this thread until Thursday when someone sent me a link.
Needless to say, we were shocked by the measurements you posted and the conclusion you drew to condemn our product as not blocking the path of leakage currents and transmitting noise and harmonics from whatever PS is used to "energize"/charge the UltraCap LPS-1.
Happily I can report and prove that you measurements and conclusions are entirely incorrect. The LPS-1 does not pass ANY AC leakage or noise from its charging supply.
What you are seeing is radiated--into the air--harmonics from the Mean Well (and iFi iPower as you showed even worse), from the brick itself, and very much from the DC cable from the SMPS to the LPS-1. The cables from your DAC to your analyzer are picking this up! (And we suspect that the output impedance of your bus-powered DAC may be a bit high, causing greater sensitivity to this--since our tests show one cheap DAC, the Micca OriGen+ was sensitive while others on hand were not.)
Before posting our graphs and photos and giving you suggestions on proving this for yourself, allow me to address a couple of other points mentioned in your opening assessment of our product:
a) You mentioned the interval at which the banks switch as 3 seconds when powering the ISO REGEN. The bank change-over rate is entirely dependent on the load. Since the ISO REGEN is the sole source of power for your bus-powered DAC, the overall load is 100mA (the ISO REGEN itself) plus whatever the DAC is drawing (perhaps 400mA? easy to check with a USB ammeter).
b) You wrote: "FPGAs are normally used when CPUs are not fast enough to do the job in software. I don't know of any design characteristics of this type of device as to require an FPGA. I am at a loss as to why this part is used other than maybe more familiarity of the designer with hardware than software. Or a way of making the design difficult to copy."
Without debating the quizzical nature of the first sentence (why would we use a full CPU for our s/w when a small FPGA is the perfect place to load and run all the code?), there are a great many reasons--having to to with charging, diagnostics, resets, over-current modes and recovery--supporting our choice to use an FPGA.
In fact, the entire design was prototyped originally with all discrete circuitry--using about 100 more parts. It became apparent that for reliability, flexibility (we can adapt the core tech to larger applications), and cost, the FPGA architecture was the only reasonable way to go.
As for "more familiarity of the designer with hardware than software," this again makes no sense, unless you are just tossing out another glib insult. There is a ton of code loaded into the board, and we used the right part for the job.
As for making the design difficult to copy, I'd like to see someone try. It is a 4-layer board with 4 power domains, a lot of fairly costly parts, and a lot of unique thinking went into it. It is also our lowest margin product as I was determined to price it for volume sales.
c) Your legend on the photo of the bottom of the board (the side with all the ultracaps) has the input and output jacks reversed.
d) Your measurements and any judgement of the merits of the LPS-1--aside from being incorrect about leakage blocking--are of course not assessing either of its other 2 key attributes.
Okay, on with the show!
LEAKAGE: Defined in the current discussion as AC harmonic current traveling over DC connections.
Your supposition, which you tried to support with the measurements you made, is that any leakage current from the PS "energizing"/charging the LPS-1, is going through the LPS-1, coming out on its DC cable, going into whatever it is connected to (in this case the downstream side of the ISO REGEN), then through the USB cable to the DAC, and out of the DAC into your analyzer. Such would be quite damning if true, and would render our entire bank-switching design superfluous. Might as well offer a traditional low noise LPS.
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.
By the way, our tests lead us to believe that almost none of what you are seeing is making its way from the SMPS into the wall and to your analyzer via mains ground pins, but without knowing all of your set up we can not be sure. In our own tests the wall connections did not make a lot of difference.
It will be easy for you to demonstrate any of this for yourself, and maybe later we can discuss a proper method for you to measure actual leakage currents from various power supplies directly (it is not hard, but we need to know about the input grounding of your analyzer to instruct you correctly).
Here we have the Mean Well SMPS energizing the LPS-1, which is powering an ISO REGEN, which is powering the Micca OriGen+ DAC you are familiar with. The 3.5mm>RCA cable in the foreground goes to our HP spectrum analyzer (12KHz signal on all graphs--just out of the displayed band):
Here is the plot for it.
Please note that for all our plots, the vertical axis is in dBm (versus dBV for Amir's graphs) and that's a 13 dBx difference. so the marker at -98.6 dBm is equivalent to -111.6 dBV.
Now here is the same set up, only this time the LPS-1 is being powered by a quiet linear supply (offscreen, our own choke-filtered, dual-rail, 5-7 amp JS-2). BUT NOTE THAT THE MEAN WELL IS STILL PLUGGED INTO THE WALL:
And the near identical plot for it:
Now we remove the Mean Well's power cord:
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.
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:
And its much quieter results, with 120Hz noise down at -131dBV:
---------------------------------------------
John got called away today, but we will follow-up soon with some direct measurements of power supply leakage--from the DC jacks that is. We will show plots of the Mean Well itself, and of our UltraCap LPS-1 being powered by it (or any other charger). The latter should pretty much show up as a flat line. We might also post the leakage of some other supplies we have measured (like the iFi iPower, though that is not a pretty sight and it would be impolite of us).
Lastly, I want to close by discussing and disclosing something interesting we found during all the kerfuffle here--mostly when we were looking into your ISO REGEN power supply measurements, which we now thing were a combination of actual leakage plus the radiated harmonics issue. It concerns the Mean Well power supplies.
Aside from the obvious fact that the 22-watt unit we originally chose for inclusion with the original USB REGEN is oversize (we could easily have gotten away with a 5-8W model) puts out more leakage than a smaller wall-wart would, there is another factor at play that is less obvious.
The world-wide governing bodies that regulate the types, efficiencies, and emissions of all AC-mains-conneccted devices have been steadily changing the rules over the years. I won't bore you wth the details--feel free to Google it--but in 2016 the law changed to requiring power adaptors with certifications to Level VI. [Being as about 50% of our business is overseas, conforming to the current laws and standards is important--customs offices will and do reject importation of power products that are not fully certified. (Germany is the worst; must have your papers!)
The original Mean Well model we chose in 2015 (GS25A07-P1J), met the Level V certification for efficiency and emissions. You can see this model in our web photos as it has a 16AWG coaxial DC cable. Middle of 2016, after the laws requiring Level VI certification took effect, my Mean Well importer (actually I bring in hundreds straight from Taiwan as the USA distributors suck) informed me that GS25A07-P1J was being discontinued and replaced with the Level VI-compliant GST25A07-P1J. Here is a photo of the two versions (don't mind the M&Ms, I love dark chocolate M&Ms as they keep me from eating too much chocolate):
As you can see, the new version--aside from having a ferrite near the box (as well as near the DC plug end, as does the older version)--has 16AWG zip cord for its cable. I was not terribly happy about it at the time (mainly because the zip cord gives it a cheaper feel and is not as supply as the coax). But aside from a slight efficiency improvement, and likely lower emissions at ultra-high frequencies which is what the EU nannies are most paranoid about--I could find no differences on their detailed data sheets.
Well... it turns out that while the units have the same specs, with the newer Level VI version being quieter in the ultrasonic range, their leakage profiles are a little different, and the zip-cord DC cable radiates a bit more AC 50/60Hz harmonics. So while it does not matter much for the LPS-1 (usually the brick and the cord go away to the floor and are not near RCA cables) I will be looking into this with regards to the default supply for the ISO REGEN.
Right now, I am not finding any small, Class I, Level VI-compliant, low-leakage "medical" supplies that have IEC320-C14 3-prong AC inlets--just Class II units with two-wire C8 jacks. Those are problematic for export and forces my hand with regards to providing international plugs. Might have to accept that headache at some point.
--------------------
Well that about wraps it up for my Saturday. Amir, I suggest that you play about a bit with various SMPS units plugged in and with their cables local to your setup. We think you will find that the single-ended cables to your analyzer are what are picking up the mains harmonics. Different analog cables, different DACs--even a change of AP input impedance (does it have a 50 ohm input)--will greatly alter what you see.
I know you love to measure noise and large jitter anomalies with you analyzer--at the output of DACs--and that's fine. But characterizing the performance of a low-noise power supply requires other methods.
As well, regarding the widespread reports of people using improved clocking, supplies, signal integrity, USB cables, and many server side improvements: Perhaps the scientific curiosity in you can lead you towards deeper study of the mechanisms at play. I bet if you were not so quick to dismiss so much out of hand--because your current measures do not immediately reveal variations--you could join others in researching how the phase-noise fingerprints of upstream variables somehow are audible even when you don't see it on your screen. (Very close in PN, right around the shaft of the signal skirt may be one place to look. More dynamic tests as others are doing may also yield insights.)
John is developing an advanced test system (I just spent a couple grand this week on development boards for the project) with the hope and expectation that we will at some point be able to blow the doors off all this and come forth with some very clear results, providing vindication for some of the firms whose legitimate products are regularly derided by a few as "snake oil." It just may take a while. Designing and producing products that people enjoy is our first priority, but for more than one project we are working on (an alternative to USB interface) we really need these more advanced measurement techniques in place to finalize and prove the efficacy (this in part because the proprietary nature of the tech we will us, unless patented, will require us to do more "show" (results) than "tell" (about the how). And sanding chips may even be in order.
I am 100% certain that most of the ASR regulars are going to quickly take pot shots at nearly everything in this long post. I'll tell you upfront that I am not going to dignify snarky, derisive comments with any reply. Nor will I indulge in taunts and BS challenges regarding blind tests. Our happy customers prove our products every day. I'm a small operation working 60+ hours a week to keep everything on track. There are LOTS of other firms--a number of them with similar products to ours--who you could as well challenge to blind-test their products that you don't believe in. I'm the easy target, but I will choose to walk away from people who don't show a modicum of civility and respect.
Thank you and good night,
Alex Crespi
UpTone Audio LLC
It has been a busy week, and since I don't generally hang out with the friendly, pitchfork wielding crowd here, I was not aware of this thread until Thursday when someone sent me a link.
Needless to say, we were shocked by the measurements you posted and the conclusion you drew to condemn our product as not blocking the path of leakage currents and transmitting noise and harmonics from whatever PS is used to "energize"/charge the UltraCap LPS-1.
Happily I can report and prove that you measurements and conclusions are entirely incorrect. The LPS-1 does not pass ANY AC leakage or noise from its charging supply.
What you are seeing is radiated--into the air--harmonics from the Mean Well (and iFi iPower as you showed even worse), from the brick itself, and very much from the DC cable from the SMPS to the LPS-1. The cables from your DAC to your analyzer are picking this up! (And we suspect that the output impedance of your bus-powered DAC may be a bit high, causing greater sensitivity to this--since our tests show one cheap DAC, the Micca OriGen+ was sensitive while others on hand were not.)
Before posting our graphs and photos and giving you suggestions on proving this for yourself, allow me to address a couple of other points mentioned in your opening assessment of our product:
a) You mentioned the interval at which the banks switch as 3 seconds when powering the ISO REGEN. The bank change-over rate is entirely dependent on the load. Since the ISO REGEN is the sole source of power for your bus-powered DAC, the overall load is 100mA (the ISO REGEN itself) plus whatever the DAC is drawing (perhaps 400mA? easy to check with a USB ammeter).
b) You wrote: "FPGAs are normally used when CPUs are not fast enough to do the job in software. I don't know of any design characteristics of this type of device as to require an FPGA. I am at a loss as to why this part is used other than maybe more familiarity of the designer with hardware than software. Or a way of making the design difficult to copy."
Without debating the quizzical nature of the first sentence (why would we use a full CPU for our s/w when a small FPGA is the perfect place to load and run all the code?), there are a great many reasons--having to to with charging, diagnostics, resets, over-current modes and recovery--supporting our choice to use an FPGA.
In fact, the entire design was prototyped originally with all discrete circuitry--using about 100 more parts. It became apparent that for reliability, flexibility (we can adapt the core tech to larger applications), and cost, the FPGA architecture was the only reasonable way to go.
As for "more familiarity of the designer with hardware than software," this again makes no sense, unless you are just tossing out another glib insult. There is a ton of code loaded into the board, and we used the right part for the job.
As for making the design difficult to copy, I'd like to see someone try. It is a 4-layer board with 4 power domains, a lot of fairly costly parts, and a lot of unique thinking went into it. It is also our lowest margin product as I was determined to price it for volume sales.
c) Your legend on the photo of the bottom of the board (the side with all the ultracaps) has the input and output jacks reversed.
d) Your measurements and any judgement of the merits of the LPS-1--aside from being incorrect about leakage blocking--are of course not assessing either of its other 2 key attributes.
- The LPS-1 offers extraordinarily low output impedance (across a wide bandwidth, and especially at low frequencies which we think is most important for its application). Plotted measurements of this are tricky to perform, but we plan to publish impedance plots in a few weeks.
- The cascaded TI TPS7A700 output regulators we use are the lowest noise (wideband) and highest PSRR integrated devices available in the 1A class. This is a VERY quiet supply. Again, environmental factors make it hard produce clean plots, but we are getting there.
Okay, on with the show!
LEAKAGE: Defined in the current discussion as AC harmonic current traveling over DC connections.
Your supposition, which you tried to support with the measurements you made, is that any leakage current from the PS "energizing"/charging the LPS-1, is going through the LPS-1, coming out on its DC cable, going into whatever it is connected to (in this case the downstream side of the ISO REGEN), then through the USB cable to the DAC, and out of the DAC into your analyzer. Such would be quite damning if true, and would render our entire bank-switching design superfluous. Might as well offer a traditional low noise LPS.
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.
By the way, our tests lead us to believe that almost none of what you are seeing is making its way from the SMPS into the wall and to your analyzer via mains ground pins, but without knowing all of your set up we can not be sure. In our own tests the wall connections did not make a lot of difference.
It will be easy for you to demonstrate any of this for yourself, and maybe later we can discuss a proper method for you to measure actual leakage currents from various power supplies directly (it is not hard, but we need to know about the input grounding of your analyzer to instruct you correctly).
Here we have the Mean Well SMPS energizing the LPS-1, which is powering an ISO REGEN, which is powering the Micca OriGen+ DAC you are familiar with. The 3.5mm>RCA cable in the foreground goes to our HP spectrum analyzer (12KHz signal on all graphs--just out of the displayed band):
Here is the plot for it.
Please note that for all our plots, the vertical axis is in dBm (versus dBV for Amir's graphs) and that's a 13 dBx difference. so the marker at -98.6 dBm is equivalent to -111.6 dBV.
Now here is the same set up, only this time the LPS-1 is being powered by a quiet linear supply (offscreen, our own choke-filtered, dual-rail, 5-7 amp JS-2). BUT NOTE THAT THE MEAN WELL IS STILL PLUGGED INTO THE WALL:
And the near identical plot for it:
Now we remove the Mean Well's power cord:
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.
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:
And its much quieter results, with 120Hz noise down at -131dBV:
---------------------------------------------
John got called away today, but we will follow-up soon with some direct measurements of power supply leakage--from the DC jacks that is. We will show plots of the Mean Well itself, and of our UltraCap LPS-1 being powered by it (or any other charger). The latter should pretty much show up as a flat line. We might also post the leakage of some other supplies we have measured (like the iFi iPower, though that is not a pretty sight and it would be impolite of us).
Lastly, I want to close by discussing and disclosing something interesting we found during all the kerfuffle here--mostly when we were looking into your ISO REGEN power supply measurements, which we now thing were a combination of actual leakage plus the radiated harmonics issue. It concerns the Mean Well power supplies.
Aside from the obvious fact that the 22-watt unit we originally chose for inclusion with the original USB REGEN is oversize (we could easily have gotten away with a 5-8W model) puts out more leakage than a smaller wall-wart would, there is another factor at play that is less obvious.
The world-wide governing bodies that regulate the types, efficiencies, and emissions of all AC-mains-conneccted devices have been steadily changing the rules over the years. I won't bore you wth the details--feel free to Google it--but in 2016 the law changed to requiring power adaptors with certifications to Level VI. [Being as about 50% of our business is overseas, conforming to the current laws and standards is important--customs offices will and do reject importation of power products that are not fully certified. (Germany is the worst; must have your papers!)
The original Mean Well model we chose in 2015 (GS25A07-P1J), met the Level V certification for efficiency and emissions. You can see this model in our web photos as it has a 16AWG coaxial DC cable. Middle of 2016, after the laws requiring Level VI certification took effect, my Mean Well importer (actually I bring in hundreds straight from Taiwan as the USA distributors suck) informed me that GS25A07-P1J was being discontinued and replaced with the Level VI-compliant GST25A07-P1J. Here is a photo of the two versions (don't mind the M&Ms, I love dark chocolate M&Ms as they keep me from eating too much chocolate):
As you can see, the new version--aside from having a ferrite near the box (as well as near the DC plug end, as does the older version)--has 16AWG zip cord for its cable. I was not terribly happy about it at the time (mainly because the zip cord gives it a cheaper feel and is not as supply as the coax). But aside from a slight efficiency improvement, and likely lower emissions at ultra-high frequencies which is what the EU nannies are most paranoid about--I could find no differences on their detailed data sheets.
Well... it turns out that while the units have the same specs, with the newer Level VI version being quieter in the ultrasonic range, their leakage profiles are a little different, and the zip-cord DC cable radiates a bit more AC 50/60Hz harmonics. So while it does not matter much for the LPS-1 (usually the brick and the cord go away to the floor and are not near RCA cables) I will be looking into this with regards to the default supply for the ISO REGEN.
Right now, I am not finding any small, Class I, Level VI-compliant, low-leakage "medical" supplies that have IEC320-C14 3-prong AC inlets--just Class II units with two-wire C8 jacks. Those are problematic for export and forces my hand with regards to providing international plugs. Might have to accept that headache at some point.
--------------------
Well that about wraps it up for my Saturday. Amir, I suggest that you play about a bit with various SMPS units plugged in and with their cables local to your setup. We think you will find that the single-ended cables to your analyzer are what are picking up the mains harmonics. Different analog cables, different DACs--even a change of AP input impedance (does it have a 50 ohm input)--will greatly alter what you see.
I know you love to measure noise and large jitter anomalies with you analyzer--at the output of DACs--and that's fine. But characterizing the performance of a low-noise power supply requires other methods.
As well, regarding the widespread reports of people using improved clocking, supplies, signal integrity, USB cables, and many server side improvements: Perhaps the scientific curiosity in you can lead you towards deeper study of the mechanisms at play. I bet if you were not so quick to dismiss so much out of hand--because your current measures do not immediately reveal variations--you could join others in researching how the phase-noise fingerprints of upstream variables somehow are audible even when you don't see it on your screen. (Very close in PN, right around the shaft of the signal skirt may be one place to look. More dynamic tests as others are doing may also yield insights.)
John is developing an advanced test system (I just spent a couple grand this week on development boards for the project) with the hope and expectation that we will at some point be able to blow the doors off all this and come forth with some very clear results, providing vindication for some of the firms whose legitimate products are regularly derided by a few as "snake oil." It just may take a while. Designing and producing products that people enjoy is our first priority, but for more than one project we are working on (an alternative to USB interface) we really need these more advanced measurement techniques in place to finalize and prove the efficacy (this in part because the proprietary nature of the tech we will us, unless patented, will require us to do more "show" (results) than "tell" (about the how). And sanding chips may even be in order.
I am 100% certain that most of the ASR regulars are going to quickly take pot shots at nearly everything in this long post. I'll tell you upfront that I am not going to dignify snarky, derisive comments with any reply. Nor will I indulge in taunts and BS challenges regarding blind tests. Our happy customers prove our products every day. I'm a small operation working 60+ hours a week to keep everything on track. There are LOTS of other firms--a number of them with similar products to ours--who you could as well challenge to blind-test their products that you don't believe in. I'm the easy target, but I will choose to walk away from people who don't show a modicum of civility and respect.
Thank you and good night,
Alex Crespi
UpTone Audio LLC
Well Alex, I have only skimmed your reply, I will look at it in detail later and respond further, but the first obvious response is why is this the first time you have hooked up a spectrum analyser to a dac output? You have obviously never done this previously.
Secondly, if a spectrum analyser is showing the meanwell is totally inappropriate for the job by radiating crap, then this will also be a problem for an audio amplifier. So why do you supply it and why do you recommend it?
Thirdly, and I will let Amir confirm this, he has tested plenty of dacs with various supplies linear and smps, and I dont recall seeing any issue with 60Hz and harmonic "pick up". In any case Im sure he can test this by placing the meanwell near to a problem free set up and see if its proximity causes the issue.
Secondly, if a spectrum analyser is showing the meanwell is totally inappropriate for the job by radiating crap, then this will also be a problem for an audio amplifier. So why do you supply it and why do you recommend it?
Thirdly, and I will let Amir confirm this, he has tested plenty of dacs with various supplies linear and smps, and I dont recall seeing any issue with 60Hz and harmonic "pick up". In any case Im sure he can test this by placing the meanwell near to a problem free set up and see if its proximity causes the issue.
Similar threads
