Objective proof the UpTone Regen ISO can improve a DAC's output(*)

[internethandle]

Amir's brief autiobiography linked by esldude doesn't really give me much confidence in who he might be. Whenever someone provides a series of unverifiable claims about their identity that all read as highly impressive (he's read "all" the books and papers on DAC measurement, he introduced the use of AP analyzers to Sony, his work on signal processing at Microsoft touched "practically any product that plays audio"(? - he seems to mean with optical media here, but I'm not sure), his measurements "have been published in magazines and reviewed by countless people in the industry and research[sic]", etc.), it tends to perk my ears a bit. I think who he is would be less important if his work wasn't potentially effecting the livelihoods and reputations of what are often times small/boutique audio companies who deserve to know who they're up against.

[esldude]

16 minutes ago, internethandle said:

That brief autiobiography linked by esldude by Amir doesn't really give me much confidence in who he might be. Whenever someone provides a series of unverifiable claims about their identity that all read as highly impressive (he's read "all" the books and papers on DAC measurement, he introduced the use of AP analyzers to Sony, his work on signal processing at Microsoft touched "practically any product that plays audio"(? - he seems to mean with optical media here, but I'm not sure), his measurements "have been published in magazines and reviewed by countless people in the industry and research[sic]", etc.), it tends to perk my ears a bit. I think who he is would be less important if his work wasn't potentially effecting the livelihoods and reputations of what are often times small/boutique audio companies who deserve to know who they're up against.

https://www.linkedin.com/in/amir-majidimehr-0014a75

 

You could read this.  He was a VP at MS when they acquired Pacific Microsonics.  At one time when JJ Johnston (if you know who he is) worked for Microsoft it was within the group Amir was VP over. 

 

I don't personally know the guy, but you can see mention of him under the Windows Media Professional Audio section here:

https://en.wikipedia.org/wiki/Windows_Media_Audio

 

Seems likely he did work at MS. 

 

He is listed as a Technical Editor at Widescreen Review at least as recently as January 2017 so that part is true.

 

Regardless of any of that, I too prefer to judge results and procedures rather than purely credentials. 

[firedog]

 

If a product isn't what I see as ridiculously expensive and sounds like the idea behind it is reasonable, I'll give it a try and see if I think it makes a difference. In the end, there are endless sources of confirmation bias - some plus and some negative - for any product, so if I "think" something sounds better - then it does. 

 

Objective truth would be good, but I don't see how we arrive at it in practical terms. Very few products are tested objectively, and even fewer by more than one person. We also often have dueling "experts" telling us why something can or can't make difference. Since I'm not an expert, I basically don't believe anyone.

 

In Amir's original testing of the Regen, he made a basic mistake, got results which even he said didn't make sense, but went ahead and published them anyway. He soon corrected them, but his "rush to publish" makes me think that he may not be an objective source - even if consciously he is trying to be. I don't see an indication that he is purposely trying to get negative results for these products, but I'm not at all sure he doesn't have a bias which affects how he tests and his results/conclusions.

 

If you read iFi's long response at their sponsored forum to his testing using the iFi iPower, they give a pretty convincing argument that just having an AP analyzer and an engineering degree doesn't show that someone is competent to use it properly. Basically, they said that Amir makes mistakes in his setup that give him false results. And he isn't aware of them, because "you don't know what you don't know", as it were. There were a couple of others on the net who tested the iFi and didn't agree with Amir's results. 

 

I'm using an IsoRegen with a galvanically isolated USB input. The manufacturer didn't think a unit like the IR would help it (but they all say that). Alex gave an honest answer and said that it could still possibly make an improvement to this kind of setup because it would apply the isolation before the USB input and not after it  (internally) - as happens in most DACs. That was an honest response, not hype. So I ordered one. So far I'm not hearing a big improvement with it. But I don't have any method for doing unsighted A/B testing, and so my impression in itself could be due to some kind of confirmation bias. I'm going to keep testing my system with and without it, and at some point will come to a conclusion.

 

If I decide it isn't doing much, I'll sell it. I'll take a small loss. But I will have learned something and hey, it's all part of the hobby. We aren't talking about saving starving children here. Sometimes (and especially over at Amir's forum) it seems that is forgotten. 

 

 

[Speed Racer]

19 minutes ago, esldude said:

He was a VP at MS when they acquired Pacific Microsonics.  At one time when JJ Johnston (if you know who he is) worked for Microsoft it was within the group Amir was VP over.

 

I worked at Apple for over 9 years. I don't have enough fingers and toes to count the Engineering VPs and Senior Directors there that could not engineer their way out of a paper bag. So Amir being a VP of an Engineering group at MS means nothing to me in regards to him testing DACs and USB decrapifiers.

[internethandle]

His Q.V. does appear to be fairly impressive if he is who he says he is and it would be quite an elaborate ruse if he isn't. Still, I suppose one could (and this seems to be the implied if not explicit position of most in the audiophile industry who have bothered to respond to his measurements) make the case that having worked on computer based audio standards and the like is not the same thing as having designed a piece of audio equipment.

 

 

 

 

 

 

 

 

[internethandle]

I'm also having trouble reconciling his measuring jitter plots/distributions and correlating them with his son reporting having heard computer activity through his DAC, which Amir posits is through the shared PC ground (this is in his semi-veiled Bifrost measurements). Objectivists I've run into tend to claim that hearing computer activity through a DAC is impossible, or that jitter numbers outside of huge spikes are inconsequential. Or take Stoddard's comments about jitter numbers mattering most at the DAC's wordclock and not its output:

 

Quote

Jitter. Oh gawd, people love jitter. They just love, love, love it. They love to throw numbers like 0.2pS at the screen and talk about “femto” clocks and how their jitter is just the lowest possible number it can be. But there are several problems with this:

 
1. The number of individuals who can actually measure sub-pS jitter is very, very, very low—it requires a $30K instrument that does exactly one thing: measure jitter


2. “Femto” clocks—clocks with femtosecond level jitter—frequently only have femto performance at very high frequencies…and are dependent on layout, logic, power supplies, PCB noise, etc, etc…so they may not really mean anything

3. Most don’t measure jitter where it matters—at the word clock to the DAC—because the number will be higher than those sub-pS readings
 
We measure jitter on all our designs at the word clock with an interval analyzer. On the best designs, we can get down around single-digit pS numbers. On other designs, it may be 50+ pS. In either case, they’re not impressive when you’re comparing to 0.2pS. So we don’t publish those measurements. Nor do we publish our eye diagrams, jitter impairment tests, and jitter spectrums from the Stanfords…but a quick look at Yggy’s jitter specs, tested here independently, confirms exceptional performance.
 
- So, how hard is it to get great jitter numbers? I could be snarky and say, “Not hard if you make them up.” But, bottom line, very hard, especially when measured where it matters.
 
- What do we shoot for? 2-digit pS in non-Adapticlock products, single-digit pS in Adapticlock products, both measured at the word clock with an interval analyzer, and correlated with a benign jitter frequency distribution as measured on the Stanford.
 
- Does jitter correlate to audible differences? It shouldn’t. Modern numbers, even on some fairly terrible interfaces, really should be below the limit of audibility. We'll leave it at that.

 

How much of what Amir is measuring, in other words, should (objectively!) be audible? I'm asking these things mostly out of ignorance and/or genuine curiosity, so please don't take me for necessarily poking holes for the sake of doing so. 

[esldude]

1 minute ago, internethandle said:

I'm also having trouble reconciling his measuring jitter plots/distributions and correlating them with his son reporting having heard computer activity through his DAC, which Amir posits is through the shared PC ground (this is in his semi-veiled Bifrost measurements). Objectivists I've run into tend to claim that hearing computer activity through a DAC is impossible, or that jitter numbers outside of huge spikes are inconsequential. Or take Stoddard's comments about jitter numbers mattering most at the DAC's wordclock and not its output:

 

 

 

 

How much of what Amir is measuring, in other words, should (objectively!) be audible? I'm asking these things mostly out of ignorance and/or genuine curiosity, so please don't take me for necessarily poking holes for the sake of doing so. 

I don't know who said you couldn't hear computer activity in a DAC.  Certainly many sound cards would let you hear mouse movements, clicks, and other things as noise via audio output.  This was what he reported for the Bifrost.  I don't know why he would make that up.  I have not yet heard any asynch USB connected device do that, though others have reported such for some DACs.  I had a Firewire audio interface that would do that with one particular laptop though not any others. I know any DAC that exhibited that I would return if it was happening with more than one computer.

 

I don't know how audible the apparent jitter in the Modi 2 would be either.  It was a topic as it has some sensitivity to the USB, and the ISO Regen did fix that. Vs other DACs that don't appear sensitive and don't appear to benefit from the Regen.  His aim I think was to see if the Regen benefited playback.  For most DACs he had on hand the answer was no.  I don't know that he is saying the Modi 2 improvement is audible using a Regen, only that it does have a measurably improved result with the Regen in place. A first step is show a difference occurs. 

[esldude]

51 minutes ago, Speed Racer said:

 

I worked at Apple for over 9 years. I don't have enough fingers and toes to count the Engineering VPs and Senior Directors there that could not engineer their way out of a paper bag. So Amir being a VP of an Engineering group at MS means nothing to me in regards to him testing DACs and USB decrapifiers.

We already know you said you didn't care what his results you wouldn't believe them.  You never did answer why?

 

I too have run into plenty of engineers who were horrible in my day job.  Worked with them for years.  I was appalled that in CE's at least about 1/3 were truly incompetent and still kept jobs.  The rest were at least okay and a few truly excellent. 

[pkane2001]

3 hours ago, Superdad said:

 

But it is completely obvious that what he is measuring are the byproducts of the leakage current loop being formed by the interaction of leakage currents between the supplied Mean Well SMPS and the SMPS of his Audio Precision analyzer!

 

Alex, so why is it that ISO Regen with its ground isolation and noise blocking capabilities isn't stopping these ground loops? I thought that's what it was designed to do?

[Superdad]

3 hours ago, pkane2001 said:

 

Alex, so why is it that ISO Regen with its ground isolation and noise blocking capabilities isn't stopping these ground loops? I thought that's what it was designed to do?

 

Because it is not a ground loop he is forming (though if he puts the ISO REGEN switch in the defeat position, his setup--using single-end connection to the AP and having the same computer connected to both the DAC and the analyzer--would surely form one of those too!).  No, he is forming an AC leakage current loop.

 

That is very different.  It is a significant, widely overlooked issue in audio (and even with measurement equipment), and it very many exists, as exemplified by Amir's graph--which he completely misinterpreted as being the ISO REGEN putting mains noise on the 5VBUS line into the DAC.

 

John has written extensively about leakage/loops.  He has explained:

• what they are (AC traveling over every sort of connection including DC connections);
• where they come from (virtually every power supply; linears have leakage though not as much as switchers, and batteries have none);
• why they form (must be two PSUs--it is the interaction between two or more);
• and how best to mitigate them (reduce impedance between gear by plugging all system mains power cords into a heavy power stirip with zero filtering elements--use a low interwinding-capacitance isolation transformer for protection of gear)

By the way, one of the hallmarks of our own UltraCap LPS-1, its raison d'etre, is that by being "battery-like" (without the performance shortcomings of batteries), it blocks the path of leakage currents.  Or I should more correctly say that it keeps the device being powered from contributing any PS leakage the system's leakage loops.  EVERY audio system has leakage loops, but the combination of the ISO REGEN and the LPS-1 is what creates a complete "moat" between the computer (with its very high and typically quite nasty and "bursty" leakage) and the DAC.

 

Remember, galvanic isolation (just one of the functions of the ISO REGEN) is the blockage of DC not AC.

[pkane2001]

54 minutes ago, Superdad said:

 

Because it is not a ground loop he is forming (though if he puts the ISO REGEN switch in the defeat position, his setup--using single-end connection to the AP and having the same computer connected to both the DAC and the analyzer--would surely form one of those too!).  No, he is forming an AC leakage current loop.

 

That is very different.  It is a significant, widely overlooked issue in audio (and even with measurement equipment), and it very many exists, as exemplified by Amir's graph--which he completely misinterpreted as being the ISO REGEN putting mains noise on the 5VBUS line into the DAC.

 

John has written extensively about leakage/loops.  He has explained:

• what they are (AC traveling over every sort of connection including DC connections);
• where they come from (virtually every power supply; linears have leakage though not as much as switchers, and batteries have none);
• why they form (must be two PSUs--it is the interaction between two or more);
• and how best to mitigate them (reduce impedance between gear by plugging all system mains power cords into a heavy power stirip with zero filtering elements--use a low interwinding-capacitance isolation transformer for protection of gear)

By the way, one of the hallmarks of our own UltraCap LPS-1, its raison d'etre, is that by being "battery-like" (without the performance shortcomings of batteries), it blocks the path of leakage currents.  Or I should more correctly say that it keeps the device being powered from contributing any PS leakage the system's leakage loops.  EVERY audio system has leakage loops, but the combination of the ISO REGEN and the LPS-1 is what creates a complete "moat" between the computer (with its very high and typically quite nasty and "bursty" leakage) and the DAC.

 

Remember, galvanic isolation (just one of the functions of the ISO REGEN) is the blockage of DC not AC.

 

Thanks, Alex. So ISO Regen does not help with AC leakage currents from its own supply, is that fair? Does that mean that LPS-1 is needed with ISO Regen to help eliminate these?

 

By the way, it's easy enough to test which supply the noise comes from. I have an old power regenerator device from PS Audio that allows me to set the power frequency from 50Hz to over 100. Having the DUT or the measuring device plugged into a different frequency mains will quickly reveal which device is leaking AC (a test I've done with my DACs).

[plissken]

7 hours ago, Superdad said:

 

Except when he demonstrates that he is when it comes to measuring devices with power supplies.  He just posted a big "Whoa, stop the presses" report claiming the ISO REGEN adds 60Hz harmonics to its output:

http://audiosciencereview.com/forum/index.php?threads/uptone-iso-regen-review-and-measurements.1829/page-6#post-46377

 

But it is completely obvious that what he is measuring are the byproducts of the leakage current loop being formed by the interaction of leakage currents between the supplied Mean Well SMPS and the SMPS of his Audio Precision analyzer!

 

Yes, we all know that SMPS have higher leakage currents due to the required 'Y' caps on their outputs.  But it takes two supplies to form an AC leakage loop, and if both supplies are SMPS then the results will be as seen.  Of course the preamps that most people will run their DACs into don't have an SMPS.  Since his AP test gear does it is obvious that his set up is the cause.

For proof, look no further than his own graph showing that with his linear bench supply the leakage spurie are decreased.  

Yet Amir erroneously concludes that the ISO REGEN is polluting the 5VBUS line!

 

This is not even the first time Amir has made this error.  He did so with the microRendu powered by the iFi iPower.

 

There are a few simple tests he could do to more clearly show this, but given his "credentials"--and the tremendous nastiness coming at us from his forum--I have zero desire to guide him.

 

Then how do you explain that the computer with a SMPS driving the Behringer cleanly?

My take away from what you are saying is a get a 5 volt 1 amp linear supply. 

[plissken]

6 hours ago, internethandle said:

Objectivists I've run into tend to claim that hearing computer activity through a DAC is impossible,

 

I've yet to see subjectivists say that. Years ago I took a balanced cable and floated the ground at the output and when SE into an amp. You could hear everything going on inside the computer. Mouse, heavy CPU events, HD access (paging operations, file load etc). 

[plissken]

6 hours ago, internethandle said:

 

How much of what Amir is measuring, in other words, should (objectively!) be audible? I'm asking these things mostly out of ignorance and/or genuine curiosity, so please don't take me for necessarily poking holes for the sake of doing so. 

 

If you read his write ups, which I don't believe you have in full based on the above post, you would see that Amir does say that some of this has no audible consequence. 

[scan80269]

4 hours ago, pkane2001 said:

 

Thanks, Alex. So ISO Regen does not help with AC leakage currents from its own supply, is that fair? Does that mean that LPS-1 is needed with ISO Regen to help eliminate these?

 

By the way, it's easy enough to test which supply the noise comes from. I have an old power regenerator device from PS Audio that allows me to set the power frequency from 50Hz to over 100. Having the DUT or the measuring device plugged into a different frequency mains will quickly reveal which device is leaking AC (a test I've done with my DACs).

Not Alex, but here's a shot at answering your questions.

 

A power supply for the ISO REGEN, such as the Meanwell SMPS, is used to power the "downstream" side of ISO REGEN circuitry (where the USB hub chip resides).  The "upstream" side is USB bus powered.  Depending on the equipment the ISO REGEN is connected to, an AC leakage loop can still exist.  For example, AC <> Meanwell SMPS <> ISO REGEN ("downstream side") <> DAC/DDC <> DAC/DDC power supply <> AC

 

Alex & John have stated that an AC leakage loop requires at least two power supplies to form.

 

Using UpTone LPS-1 to power the ISO REGEN is one excellent way to break this AC leakage loop, though running the ISO REGEN off a battery (with proper DC voltage) should also work.  Other ways would be to power the DAC/DDC with LPS-1 or battery (if applicable).  Once you understand how the AC leakage loop is formed and what components are involved, there is often more than one method or location to break it.

 

[pkane2001]

21 minutes ago, scan80269 said:

Alex & John have stated that an AC leakage loop requires at least two power supplies to form.

 

Hi Scan,

 

I understand that LPS-1 might help to break up these AC leakage currents, this goes back to the recommendations you made to power SU-1 DDC with one of these  I guess it is then important to buy ISO Regen and LPS-1 as a package, otherwise you are leaving some noise 'on the table', so to speak, or maybe even adding some additional noise due to the Meanwell SMPS that wasn't there before inserting ISOR.

 

If two power supplies are required for an AC leakage loop to form, does that mean that the loop is formed by the common wiring (in the wall) shared by both power supplies? Can you please describe or draw a high-level pathway of how this leakage current occurs between devices and power supplies, it seems a bit hazy in my mind?

[tmtomh]

2 hours ago, skew said:

If you read his write ups, which I don't believe you have in full based on the above post, you would see that Amir my love does say that some of this has no audible consequence. 

 

So @skew, you're a new member and had a grand total of 2 posts here, and you thought it would be cute or in some way relevant to quote plissken's comment, amending it to say "Amir my love"? Are you an infant? What are you, 9 years old? Totally bush league. Wouldn't mind if Chris booted you from the forums.

[Superdad]

At the airport so I'll skip quoting.  But I just thought I would reiterate that typically the device (DAC, DDC) that the ISO REGEN is feeding does not have an SMPS, so while a leakage loop will still form (more likely just be added to as loops between the DAC and preamp supplies already exist), it won't produce nearly the harmonics that would be seen between two SMPS--as in Amir's test set up with AP analyzer's SMPS.

 

To quickly address plissken's Q:  I recall that Amir uses a laptop, and while I don't know if he runs it on battery, one can still see spikes from direct computer to DAC connection.  

[scan80269]

40 minutes ago, pkane2001 said:

 

Hi Scan,

 

I understand that LPS-1 might help to break up these AC leakage currents, this goes back to the recommendations you made to power SU-1 DDC with one of these  I guess it is then important to buy ISO Regen and LPS-1 as a package, otherwise you are leaving some noise 'on the table', so to speak, or maybe even adding some additional noise due to the Meanwell SMPS that wasn't there before inserting ISOR.

 

If two power supplies are required for an AC leakage loop to form, does that mean that the loop is formed by the common wiring (in the wall) shared by both power supplies? Can you please describe or draw a high-level pathway of how this leakage current occurs between devices and power supplies, it seems a bit hazy in my mind?

Per my understanding, yes.  The two AC power cords and the common wiring (in the wall) form part of a specific AC leakage loop.  The loop involves both AC and DC sections of each power supply.  Both SMPS (switching) and LPS (linear) supplies will contribute to AC leakage, though the SMPS are typically the worse offenders.

 

Let's take my previous example and elaborate a bit further.  We'll start at an AC wall socket.

 

AC wall socket #1 <> AC power cord <> Meanwell SMPS <> DC power cable <> ISO REGEN ("downstream" side) <> USB cable <> DAC/DDC <> internal DC cabling <> DAC/DDC power supply <> AC power cord <> AC wall socket #2

 

The common wiring (in the wall) completes the above AC leakage loop.

 

ISO REGEN serves to block noise and clean up USB signal coming from a dirty upstream USB port, such as from a PC.  The IR by its design does not offer blockage against AC leakage loops such as the above.  Since power supplies are always involved in the forming of an AC leakage loop, the task to break the loop largely falls to one (or more) of the involved power supplies.  UpTone LPS-1 is a linear power supply that has highly effective blockage against AC leakage loops.  Think of it as a firewall against AC leakage currents.  A DC battery also has this capability by virtue of not having a connection to AC whatsoever.

 

When you power an ISO REGEN with LPS-1 supply or battery, you achieve "total" isolation from the dirty upstream USB source, as well as freedom from an AC leakage loop.

 

Hope this helps!

 

[Superdad]

@scan80269 should receive a stipend for so kindly answering on our behalf. Thanks! 

[pkane2001]

4 hours ago, scan80269 said:

Per my understanding, yes.  The two AC power cords and the common wiring (in the wall) form part of a specific AC leakage loop.  The loop involves both AC and DC sections of each power supply.  Both SMPS (switching) and LPS (linear) supplies will contribute to AC leakage, though the SMPS are typically the worse offenders.

 

Let's take my previous example and elaborate a bit further.  We'll start at an AC wall socket.

 

AC wall socket #1 <> AC power cord <> Meanwell SMPS <> DC power cable <> ISO REGEN ("downstream" side) <> USB cable <> DAC/DDC <> internal DC cabling <> DAC/DDC power supply <> AC power cord <> AC wall socket #2

 

The common wiring (in the wall) completes the above AC leakage loop.

 

ISO REGEN serves to block noise and clean up USB signal coming from a dirty upstream USB port, such as from a PC.  The IR by its design does not offer blockage against AC leakage loops such as the above.  Since power supplies are always involved in the forming of an AC leakage loop, the task to break the loop largely falls to one (or more) of the involved power supplies.  UpTone LPS-1 is a linear power supply that has highly effective blockage against AC leakage loops.  Think of it as a firewall against AC leakage currents.  A DC battery also has this capability by virtue of not having a connection to AC whatsoever.

 

When you power an ISO REGEN with LPS-1 supply or battery, you achieve "total" isolation from the dirty upstream USB source, as well as freedom from an AC leakage loop.

 

Hope this helps!

 

 

Thanks, Scan! That makes sense.

 

What is still not apparent to me is what other effects ISO-R has on noise and leakage currents beyond what might be solved by LPS-1 (or a battery). While it might be that LPS-1 will fix the AC leakage currents that show up in Amir's measurements with SMPS, and the 5v line is also cleaned up, I don't see any other effects of ISO-R on noise or jitter.  Also, the AC leakage currents don't seem to be a problem for a few of the other DACs that he had on the bench, so there may not be a need in LPS-1 for these?

 

[plissken]

5 hours ago, tmtomh said:

 

So @skew, you're a new member and had a grand total of 2 posts here, and you thought it would be cute or in some way relevant to quote plissken's comment, amending it to say "Amir my love"? Are you an infant? What are you, 9 years old? Totally bush league. Wouldn't mind if Chris booted you from the forums.

 

I reported the post. Would help if others did also. 

[plissken]

5 hours ago, Superdad said:

At the airport so I'll skip quoting.  But I just thought I would reiterate that typically the device (DAC, DDC) that the ISO REGEN is feeding does not have an SMPS, so while a leakage loop will still form (more likely just be added to as loops between the DAC and preamp supplies already exist), it won't produce nearly the harmonics that would be seen between two SMPS--as in Amir's test set up with AP analyzer's SMPS.

 

To quickly address plissken's Q:  I recall that Amir uses a laptop, and while I don't know if he runs it on battery, one can still see spikes from direct computer to DAC connection.  

 

And I believe that Amir did point out that he is very zoomed in and that what your PS is doing, while not optimal is simply inconsequential to SQ. It doesn't technically improve things with the Behringer so the advice is the $$ needn't be spent. 

[plissken]

48 minutes ago, pkane2001 said:

 Also, the AC leakage currents don't seem to be a problem for a few of the other DACs that he had on the bench, so there may not be a need in LPS-1 for these?

 

 

Correct barring any instrumented results posted to the contrary. Power supplies always feed back into the common house wiring. 

 

It's the power supplies job to deal with this however. 

 

Given that you can get a 15,000 mha USB battery pack for $20 on Amazon I don't see a reason that you couldn't run a lot of DAC's out there on this for a very long time if you are paranoid about the SQ and AC leakage currents.

 

Nothing I've seen or heard so far would convince me it's a problem for most DAC's. The power supply in my Emotiva DC-1 is pretty robust and most likely takes care of the issue. 

[plissken]

11 hours ago, Superdad said:

which he completely misinterpreted as being the ISO REGEN putting mains noise on the 5VBUS line into the DAC.

 

Maybe it isn't but it's not there with his lab supply. His lab supply does take care of a 180Hz bump that was their with USB bus power.

 

Three different ways of powering the ISO Regen and one of them makes the 60Hz noise the worst and the knock on harmonics.