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PostPosted: Sun Feb 17, 2013 7:05 am 
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Folks,

It is really quite hilarious to behold. There are some poor sods trying to find the "best" regulator... How do they do it?

"John Walton and the New Jersey Audio Society did test 13 different regs in Linear Audio Vol 4, measurements as well as controlled listening tests. He used as 'load' a Borbely-type preamp known for not-so-hot PSRR."

The regulators tested vary widely in all parameters, be it noise, impedance and PSRR.

There are some measurements of the different regulators here:

http://www.linearaudio.net/index.php?option=com_content&view=category&layout=blog&id=39&Itemid=64

So audible differences are to be expected and are indeed observed in listening. Here their table of results:

Image

But where it gets funny. They assign "sound quality" to each regulator, even have observations of what the regulators sound like... So where does all of this go wrong?

They are still trying to rate the best "super regulator" when in fact such a thing is futile. There is no universal best super regulator and never will be. Most of their rankings will change dramatically if for example we do not feed a Linestage but a clock. And if we feed a CMOS Delta Sigma DAC the rankings will vary again and should we supply a a classic R2R DAC they will vary again.

One must understand the behaviour of regulator circuits and of the circuits supplied by the regulator and select the correct compromise. And I must say that I am disappointed that the published of Linearaudio did not bring this out in his publication (as should be his duty and as he should know) and instead prances about a peacock about how well his own design did in this particular test.

In many ways this parallels the whole search for the best capacitor. The truth is that as we need to match regulator to application, so do we need to match capacitors to application.

There is no "absolute best" that is best in all applications, there are only many imperfect devices that need to be correctly matched to the application to get performance even better than the best "superregulator" at much less BOM cost and complexity than even low ranking "universal super regulators"...

I could now pontificate how my "super-regulator" that I implemented in a commercial product, performs ever so much better in ALL domains than most of the regulators shown in this test (and it beats all of them in at least one aspect). But I shall not, as I know that in each given specific domain I can do much better than this "universal" regulator and so I can always beat this design in any application with simpler, but better performing circuits.

Ciao T

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PostPosted: Sun Feb 17, 2013 7:16 am 
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Thorsten, Why don't you post there, as fas as I know you are not banned there.

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PostPosted: Sun Feb 17, 2013 7:48 am 
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Elso,

Elso Kwak wrote:
Thorsten, Why don't you post there, as fas as I know you are not banned there.


I did attempt previously a few times to post something after the last ban, as my account is not marked as banned or sin-binned, no posts appeared. So it appears I am "banned in secret".

You may observe that both my signature and avatar picture (which were anti censorship statements) have been suppressed as well, meanwhile my facebook page has been added (not by me) to the profile page.

Moreover, it seems some posts have been removed from old threads quit recently as well, posts that would put some other contentious ones in context... It seems TPTB over at diyaudio.com prefer to avoid the outright appearance of a ban, yet they also prefer to suppress my views and opinions and any new posts, never mind old ones.

I would like to start a discussion here on power supplies and relative effects, as at least we will not have the usual suspects jumping on it and promoting their design and trying to make thing appear in ways that suggest they version of truth is right.

This particular set of data allows us to compare objective and subjective performance in a specific application (the Borbeley Line Stage) and as it contains mostly well known designs we should be able to cross correlate design features / objective performance and subjective sonics. Surely such a thing is worthwhile?

Ciao T

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PostPosted: Sun Feb 17, 2013 8:11 am 
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Clear enough. :(

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PostPosted: Sun Feb 17, 2013 12:20 pm 
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Yes, I have read Linear Audio Vol.4 publication.
Extensive measurements tests were performed, final judgment is done by listening. A lot of effort to find correlation between measured values and listening impressions, to find out what makes a "great regulator" and what makes a "disappointing regulator".

One of more interesting sentences about TPTB:
"Stuart Yaniger suggested that we forsake the trendy, high performance audio operational amplifiers like the OPA637 or 49720 and choose a line amplifier with more humble power supply performance."

I must say I'm a little dissapointed, opamps line stages were not tested :D

Walt Jung's Letter-to-the-editor is here: http://www.linearaudio.net/images/stories/WJ%20to%20JW%20V4.pdf


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PostPosted: Sun Feb 17, 2013 2:00 pm 
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It would seem to me, an admitted and proud amateur in the audio world - there, I said it! - that there should be an attempt made in designs to separate the variables of a real system. That is, to what extent is the regulator filtering out crap that appears on the AC mains connection and migrates through to the supply lines (plus whatever crap is generated in the rectification process) and to what extent is the regulator controlling the return currents for the audio circuitry? Two different problems.

Personally, I think asking a regulator to do both well is not a great idea. Too hard. But, that's just me.

Although a lot of effort was put into this test, it's hard to know what the conclusions really mean.


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PostPosted: Sun Feb 17, 2013 2:48 pm 
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Hi,

Thanks for this, it adds additional bits.

stormsonic wrote:
One of more interesting sentences about TPTB:
"Stuart Yaniger suggested that we forsake the trendy, high performance audio operational amplifiers like the OPA637 or 49720 and choose a line amplifier with more humble power supply performance."


In a linestage this may very well be true. I would probably have suggested Borbeleys non-nfb line stage.

Instead they apparently went with this:

Image

Now exactly why anyone would consider this circuit to have poor PSRR is beyond me, it will do quite horrorshow. I can nly estilate, but with the K170/J74 being in the region of 50K+ as CCS and more in this circuit it has at least 20dB inherent PSRR, probably more.

The Amplifier has around 60dB open loop gain, if we take this with a linestage gain at 12dB, we should have around 68dB PSRR up to around 5KHz or so, not bad at all I would say. It would have been good if this test would have actually supplied measured data for the linestage.

We also know that the PSU usd 4,700uF/0.68R/4,700uF per rail with maybe 50mA total current consumption.

PSUD predicts 26mV Peak-Peak ripple with this arrangement, I'd expect 10mV RMS, so if we were not using any regulator at all, I'd expect 5uV 100Hz and much less higher up. To put this into perspective, we are talking here about around -106dBV 100Hz noise.

I would suggest that in fact parameters like self noise and PSRR of any of the regulators in the selection put things well beyond "good and bad", any regulator that can manage 40dB ripple rejection would drop PSU noise below 24Bit levels and way below the circuits self noise.

So in effect, any differences between the regulators would be down to supply current modulation and the resulting error voltages feeding back into the circuit. I would further add that with the presence of local 220uF decoupling capacitors most of the differences heard could be simply down to interactions between these cap's and the regulator and dynamic current demands.

It is interesting to note that the output impedances of the top rated regulators vary quite widely, however three of the top five have very low output impedance, with only the Burson regulator showing a quite high impedance. The Linear Tech regs coming next also have high output impedance.

To me this suggests that the real factor affecting sound quality was not sufficiently captured in the test.

I would like to offer a hypothesis though. The source used was an SACD Player. These are known for prodigious levels of supersonic and low RFI noise on their output. The Borbeley Line stage has very wide bandwidth, but was decoupled only with 220uF electrolytics, which are likely next to useless above around 100KHz (see Bateman), so at very high frequencies within the operating bandwidth of linestage the circuit relies primarily on the regulator for rail impedance and this will be all over.

This will be made worse by the fact that the following Amplifier is also quite wideband, the interconnects offer minimal if any RFI filtering themselves and that the following Amplifier is comparably non-linear, not grossly so, but certainly more than one may wish if one has a lot of RFI riding down the line.

Clearly, two regulator designs will show themselves superior in this case, for one those that start out with extremely low impedance (Jung/Didden) as they will still have comparably low rail impedances at high frequencies, the others will be very wideband designs, which I believe applies to the Burson and Linear Tech designs.

Only a hypothesis and one that requires taking into account wide ranging factors, however, the perhaps crucial lesson is that we must account for a wide range of factors in such tests and even more so in designing gear.

Ciao T

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PostPosted: Sun Feb 17, 2013 3:43 pm 
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I'd suggest the following points.

Ever look with a spectrum analyzer at what's coming out of the AC mains? At least over here in the colonies, there's a high level of stuff between 50 KHz and maybe a MHz. What do these regulators do at these frequencies? What is the PSRR of the amplifier there? How much rejection does the raw supply offer at the frequencies? Why might this matter?

At what frequency will the rectifier diode turn-off excite the transformer secondary along with associated capacitance?

Just what path will the amplifier output JFET and the input stage currents take? (Ever look at the spectrum of these currents? LTSpice will even give some perspective here.) How does the regulator under test affect this?


My own stupid opinion is that the problem is more complex than meets the eye, although it can be analyzed. A Dirk Gently like solution is what is needed for best results.


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PostPosted: Sun Feb 17, 2013 5:11 pm 
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Kuei Yang Wang wrote:
Hi,
Instead they apparently went with this:


No, much simpler, something like this, with only 4 active devices (all JFETs):

Image

I could post exact schematic, but would like permission from Jan Didden, to reproduce part of his publication.


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PostPosted: Sun Feb 17, 2013 5:21 pm 
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Hi,

stormsonic wrote:
No, much simpler, something like this, with only 4 active devices (all JFETs):

Image


That does not look like a Bona Fide Borbeley design. This design STILL has quite decent inherent PSRR.

If you like you can send me the scan off-line and I will redraw the circuit in Tina (avoiding copyright issues) and into the Bargain do a full Sim run on the PSU related behaviour open and closed loop.

Ciao T

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PostPosted: Sun Feb 17, 2013 5:50 pm 
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What a crock!

I thought everything sounds alike, and the only thing that matters are measurements, like THD.

And the "subjective comments"..........it reads just like all the stuff they routinely mock. Stinking hypocrites.

Quote:
And I must say that I am disappointed that the published of Linearaudio did not bring this out in his publication (as should be his duty and as he should know) and instead prances about a peacock about how well his own design did in this particular test.


Surely, you jest!

"No. And don't call me 'Shirley'."

(Actually, it wasn't his design. It was the "improved" version.) (And they did measurements of 2 different types, 797 vs evil 825, yet do not have comparative listening tests. How can we conclude the test were exhaustive?)

And just how well controlled were these tests? I saw the mention of wine, used in conjunction with the listening. We are to conclude their aural acumen was not impaired? Well, I put forward that these tests are not valid, and consist of no more than anecdotal musings of audio designer wanna-be drunks. How these flaws could have escaped the impartial eagle eye, of the renowned researcher, Dr. Polymer, baffles me.

Maybe he supplied the wine, so that makes it all ok.

All I can conclude is, just like everything else they preach, it only matters if it is the right preacher. Otherwise, it is just the ramblings of a bitter, old drunk, living in the past, and on the generosity of corrupt snake oil salesman, who fleeces the unwashed masses. (Who they must destroy, lest he buy another luxury classic auto.)

Shirley, I jest.

"Who is 'Shirley'? And is she single, good looking, and not like those fat boilers you hang out with?"

Image

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PostPosted: Sun Feb 17, 2013 6:03 pm 
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Hi,

CG wrote:
I'd suggest the following points.


Good points.

CG wrote:
My own stupid opinion is that the problem is more complex than meets the eye, although it can be analyzed.


That is for sure. The issue with SACD is that RFI levels are several 100mV regardless of signal level. Even when playing CD. Clip a scope on the output of one...

Considering this and old Bill of Occams dictum, we do not needs to look for 10's of mV RFI on the secondary of the transformer or riding on the DC, the noise mixed with the signal suffices to cause untold mischief.

In the end we both are looking at RFI effects folding back into the audio band as the cause though...

CG wrote:
A Dirk Gently like solution is what is needed for best results.


You mean Richard McDuff's Sofa?

Ciao T

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PostPosted: Mon Feb 18, 2013 4:44 pm 
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Hi,

stormsonic wrote:
I could post exact schematic, but would like permission from Jan Didden, to reproduce part of his publication.


Ok, I got what they use now. It is a modification (mostly ill considered I'd add) of a circuit shown in "The All-FET Line Amp" by Erno Borbely in audioXpress 5/02 as figure 5. This circuit is actually NOT the "All-FET Line Amp" but one of stages shown by EB to arrive at the fully elaborated circuit which is a whole different kettle of fish. Anyway, here is what they used.

Image

I do not have the exact models for 2SK170 and 2SJ74, however I fudged something. I get something not miles of what EB noted as performance.

I get around 20dB PSRR on each rail, not completely symmetric and around 2MHz closed loop bandwidth. More crucially, above around 100KHz for my models PSRR goes to hell in a handbag becoming even negative (PSU noise is amplified, not suppressed) below it is basically flat.

Cascoding the first fet pair would dramatically improve this situation, BTW.

Ok, so much for now.

Ciao T

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PostPosted: Mon Feb 18, 2013 5:32 pm 
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Are we supposed to be surprised? I bet none of them could tell the difference between that, and the evil 4558, right?

At least if you listen to one of those clowns.

(But then if you "fix it", by adding a cascode, then you will get lectured by Zane Grey Rollins.)

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PostPosted: Mon Feb 18, 2013 7:22 pm 
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Yes... Sofas have caused loads of confusion and unexplained results throughout history. As have women named Shirley.


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