Author Topic: How important is Power Supply Design?  (Read 5260 times)

Offline steve

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Re: How important is Power Supply Design?
« Reply #15 on: September 04, 2018, 11:58:29 AM »
Steve,

The white paper is good stuff. Thanks also for clear thinking and speaking the truth, it's most refreshing.

I remember those first EE courses well. Those fundamental laws remain the same and need to be thoroughly understood to do good work that passes muster. Prof's William Hayt and Gerry Neudeck or their TA's personally drilled it into me back then. The creative art comes in when one ventures off the script of application notes and textbook reference designs (other people's work), and the designer tries something original or unique. Their exams always had a few of these "ringers" on them you'd never seen before, just to make sure we used our brains to think for ourselves. Fortunately, the analysis using those laws, remained the same, and never let you down. Thinking you could somehow "trick" or conveniently ignore them never worked out well  :) Then, of course, there is the effect of real world factors - components, circuit layout, variability, etc. to deal with. As you know, that's part of the fun in it.

For the benefit of all, I hope everyone tries to keep it a respectful and informative dialog. Please carry on.

Thank you Tom for those kind words. Much appreciated. As you stated, there is a lot more to consider, such as layout, variability etc.

As just a couple of examples to demonstrate Tom's fine points, for the general public's consumption.

This example I have not seen anywhere except in tube manuals, is how the input Z of either a tube or solid stage gain device can vary.

Let's take a tube. The grid is not infinite impedance (Z) by any means, simply due to some DC leakage current caused by various problems. These include

1. a minute amount of gas,
2. cathode material vaporizing and depositing on the grid itself,
3. heating of the grid from the cathode's proximity, causing emission, etc. etc.

Second example, a variable. Of just as much or larger concern are the internal capacitances present. Grid to Cathode,  Gate to Source) are generally fairly small, but still relevant. An input capacitance of just 1.5 pf, lowers the Grid input
Z to ~5.3 megohms at 20khz (grounded cathode, source).
 
A much greater problem is the Miller capacitance, which is 1+ Av gain times the Grid to Plate capacitance (Base to Collector, Gate to Drain). The Grid input Z again drops significantly with frequency.

For example, with a 12AX7 tube, the G/P capacitance is ~1.7 pf. Let's use 50 as the gain. The Grid to Plate Miller capacitance is ~86pf, plus ~2pf G/C, plus stray capacitance. Let's just use 88pf. The Grid input Z now drops to only ~89k ohms at 20khz.

If one uses a 100k grid resistor, paralleling the 89.7k ohm Z, we get ~47k ohms Grid input Z at 20 khz. (Let's forget any phase angles.) So much for the 100k ohm resistance we think is the Grid input Z. Normally, however, 47k ohms is not a problem since the coupling capacitor's Xc is very very low. However, there is almost always a "but" to consider.

But, what if the preceding stage has a plate load resistor (RL) of 100k ohms. Its load line will substantially shift due to the 47k ohms load connected in parallel (at 20khz). So the harmonic and intermodulation distortion (IMD) products will almost certainly increase as the frequency rises.

With a 6DJ8 type tube, this is not quite the problem since the RL is much lower, maybe 5k ohms. However, the load line will shift to some extent as the frequency increases.

cheers

steve

ps. What the heck. Let's do an example with a 6dj8 type tube.

G/P capacitance is ~1.4pf.
G/K capacitance is ~3.5pf
Av gain               is 10 (20db gain)

Grid input Capacitance is ~14pf + 3.5pf = ~18pf
Grid input Z at 20khz =  ~442k ohms (12AX7 is ~ 89k ohms)



« Last Edit: September 04, 2018, 12:23:24 PM by steve »
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Offline rollo

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Re: How important is Power Supply Design?
« Reply #16 on: September 06, 2018, 07:21:33 AM »
    The heart of every component is the PS.


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Offline tmazz

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Re: How important is Power Supply Design?
« Reply #17 on: September 06, 2018, 02:18:40 PM »
I had an engineering professor as an undergrad who explained and amplification device, whether a tube or a transistor in very simple terms. said that a gain device to not really "amplify" anything. What it is actually doing is modulating a low voltage input signal against a higher voltage power supply rail.

Now we all know that is is much more complicated than that when you look down into the minutia, but this simplistic concept can easily drive home the point of how important power supplies are in audio applications. If the input signal is simple being used to drive changes in the higher voltage of the power supply output is is fairly obvious that and noise, hash, voltage fluctuations or anything other than a perfectly flat B+ voltage will ultimately become part the output signal as distortion of some type.

Now a great power supply in and of itself cannot guarantee great sound as there are many other things that also need to be done right. However cutting corners and building a sub par power supply, while it may not lead to poor performance, will certainly limit the performance of the component, no matter how good the rest of the design is.

And while there can be varying opinions of what constitutes the "best" power supply designs (and some of them have been debated already in this thread)  going back to the original question posted in this thread I think we can all pretty much agree that power supply design is pretty much the bedrock of any high end audio component.
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Offline Folsom

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Re: How important is Power Supply Design?
« Reply #18 on: September 07, 2018, 12:36:27 AM »
I'm not going to go in circles talking about power supply caps that magically become signal capacitors...

And I'm not going to work against all the absurd assertions.

What I will leave you with, is that I've never designed any kind of classD amplifier, EVER. I'll leave the algebra exercises to you. May you produce many thrilling products with it.

Offline steve

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Re: How important is Power Supply Design?
« Reply #19 on: September 07, 2018, 07:50:44 AM »
I'm not going to go in circles talking about power supply caps that magically become signal capacitors...

And I'm not going to work against all the absurd assertions.


We are not talking magically become "signal capacitors", but AC signal current through a capacitor. In this case AC musical signal current.

Folsom, three engineers in this string alone state my white paper is correct, as well as the RCA Radiotron Designers Handbook (26 engineers, 1960 edition), for starters.

The diy "leaders" have obviously mislead you and others.

Here is a schematic of a signal generator and two legs, each with C1 in series with R1 to ground. Notice the left C1 and R1 are opposite of the right R1 and C1. Please "check" the correct response(s)?

A. Signal generator current flows through neither left or right series resistor and capacitor.
B. Signal generator current flows through the left C1/R1.
C. Signal generator current flows through the right R1/C1.

This is basically a high school electronics question.


« Last Edit: September 07, 2018, 08:39:57 AM by steve »
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Offline Folsom

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Re: How important is Power Supply Design?
« Reply #20 on: September 07, 2018, 10:11:36 AM »
I'm not saying your circuits or math are wrong. It's the conclusion: " The power supply should properly handle all frequencies when supplying DC to a stage. This is virtually never considered let alone addressed in any designs, including the least and most expensive designs."

Now I'm done.

Offline Nick B

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Re: How important is Power Supply Design?
« Reply #21 on: September 07, 2018, 11:03:28 AM »
Is there a way to test these diverging opinions?
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Re: How important is Power Supply Design?
« Reply #22 on: September 07, 2018, 01:07:33 PM »

Offline gander

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Re: How important is Power Supply Design?
« Reply #23 on: September 07, 2018, 01:11:18 PM »
Is there a way to test these diverging opinions?
Nick

Sure, compare the two ideas by actually building each of them, and then measure and hear the differences.  I can't tell you how many times I have bought gear based on theory, and my ears were often disappointed.  There is no substitute for actually building multiple versions of a thing and listening to the differences.

And there are other possibilities of course.

For my current power solution for my LDR passive preamp and my small summer Tripath stereo amp (I would use my tube preamp in the summer if it was cooler here! I hate the heat in Las Vegas), I currently use 12V BatCaps as the power source, with iFi-Audio DC iPurifiers for each and I'm very pleased with the results.  But who knows what I might try in the future?

Just my 2 cents.

Gary
« Last Edit: September 07, 2018, 01:22:17 PM by gander »
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Offline steve

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Re: How important is Power Supply Design?
« Reply #24 on: September 07, 2018, 01:34:47 PM »
I don't know how not to be offensive; how does one respond to someone who can't answer my basic high school electronics question above, can't provide any info from engineering books, even high school books, and lies by claiming he know more than two EEs, and me, claiming my white paper is a fraud.

The Thevenin Equivalent Circuit, Kirchoff laws, and Norton Laws must be obeyed. Can't sneak around it folsom, as hard as you might try. Diy community is clearly losing reputation as they argue against those laws.

Ok, the capacitive reactance, Xc, of decoupling capacitor is in series with RL. Thevenin proves that. The basic "high school" equation for Xc is 1/2PI times F times C. 1/2PI x F x C. So RL total is RL plus Xc.

RL total varies with frequency, so the gain varies with frequency. The tonal balance is altered when one changes the value of the decoupling capacitor (Xc).
 
That is iron clad first semester electronics, maybe even high school. Anyone who does not believe that is pushing snake oil.

Folsom, still waiting for you to answer my above question with A, B, C possible answers.

cheers

steve
« Last Edit: September 07, 2018, 02:34:35 PM by steve »
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Offline steve

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Re: How important is Power Supply Design?
« Reply #25 on: September 07, 2018, 02:33:09 PM »
Is there a way to test these diverging opinions?
Nick

Sure, compare the two ideas by actually building each of them, and then measure and hear the differences.  I can't tell you how many times I have bought gear based on theory, and my ears were often disappointed.

Gary

Gary, the difference is theory is not law, but Thevenin, Kirchoff, Norton are laws. The answer is it was not the laws, but the so called theory that failed you. Their theories don't follow the laws, as folsom and his diy leaders just demonstrated through folsom's posts. You have been cheated Gary.

Secondly, designs that did not sound right? I agree Gary. They were probably making up theories, instead of using laws.

------------------
For general public consumption.

Not surprising since most designers either don't understand the laws, or follow the laws, especially diyers. Some large companies either don't understand the laws, or they don't want you to understand. Marketing, shilling, con jobs is big business. 

For instance, capacitors have ESR, DA, and inductance problems. So whose capacitors are accurate? Well, every manufacturer claims his is. So who is right? Well, if you read some forums strings, and diyers, either one of two opinions exist.

1. All capacitors sound the same. Surprise, your component does not sound right (although junk capacitors and parts, poor designs were used, poor venue for testing, poor selection of music etc.).

2. We tested different brands and found, X, brand was the best. Problem is, they tested wrong, so the best, most accurate capacitor, Y, became extinct, because Y was judged bad by incompetents.

True example. X capacitor was judged to be better than Y etc. because Y was bright sounding in the circuit. But the problem was the value of the capactors tested were too small of value. If the proper size were used, Y would have won.

(How did this happen? Because years ago, SETs guys had problems with overloading their small amplifiers and a burp would be heard. We can eliminate the burp by using a smaller capacitor. (Of course, the frequency response won't be flat.)

They would use 0,47uf, 0,82uf coupling capacitors (tube circuits), to eliminate burp, gain more prominent midrange. But it sounded thin with Y capacitor. But X capacitor sounded better because it was designed to sound more full, for a given value/size. So Y capacitor went into the bin, and became extinct.

Eliminating the burp also allowed individuals to use less efficient speakers, so larger marketing audience.
A few, even reasoned that the old time radios used them, better midrange, so who cared about natural bass, the full range anyway.

I have tested many brands, and the most accurate sounding capacitor (and fairly inexpensive) is now extinct. All the other inferior caps are still being sold, still the best. And now we have the super expensive caps, which I can't afford to test. 

Improper testing, and improper size by individuals and diyers led to the crappy state we are now in. It is all about money and looks.

So that is why theory has a bad reputation. Use poor designs/theory, and poor quality parts, which don't follow the laws of science.

But the laws are still in force and they do work. That includes parts quality as well. If they would follow them, components would sound a lot better. But anyone can make a buck if they call themselves a designer and push the snake oil. Who is to know?

cheers

steve
« Last Edit: September 07, 2018, 03:45:30 PM by steve »
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Offline gander

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Re: How important is Power Supply Design?
« Reply #26 on: September 07, 2018, 02:47:53 PM »
Is there a way to test these diverging opinions?
Nick

Sure, compare the two ideas by actually building each of them, and then measure and hear the differences.  I can't tell you how many times I have bought gear based on theory, and my ears were often disappointed.

Gary

Gary, first, these are not theories, but laws. So what happened that the laws failed you? The answer is it was not the laws, but the amateurs who failed you. Don't blame the laws.

Secondly, disappointed in what? Designs that did not sound right? Not surprising since most designers either don't the laws, or follow the laws, especially diyers. And some large companies either don't understand the laws, or they don't want you to understand. Marketing and shilling is big business. 

For instance, capacitors have ESR, DA, and inductance problems. So whose capacitors are accurate? Well, every manufacturer claims his is. So who is right? Well, if you read some forums strings, and diyers, either one of two opinions exist.

1. All capacitors sound the same. Surprise, your component does not sound right (although junk capacitors were used).

2. We tested different brands and found, X, brand was the best. Problem is, they tested wrong, so the best, most accurate capacitor, Y, became extinct, because Y was judged bad by incompetents.

True example. X capacitor was judged to be better than Y because Y was bright sounding in the circuit. But the problem was the value of the capactors tested were too small of value.

Why? Because years ago, SETs guys had problems with overloading their small amplifiers and a burp would be heard. We can eliminate the burp by using a smaller capacitor. (Of course, the flat frequency response won't be flat.

They would use 0,47uf, 0,82uf coupling capacitors (tube circuits), so no burp and more prominent midrange. But it often sounded thin. But X capacitor sounded better because it was designed to sound more full, for a given value. So Y capacitor went into the bin, and became extinct.

I have tested many brands, and the most accurate sounding capacitor (for less than $30.00) is now extinct. All the other inferior caps are still being sold.

Improper testing, and improper size by diyers and others led to the state we are now in. It is all about money and looks, not sound.

So that is why theory has a bad reputation. Of course, many if not most make up theory to SELL their products. And unfortunately, many if not most either don't follow the laws of electronics, or their marketing theory doesn't follow the laws of electronics.

But the laws are still in force and they do work. That includes parts quality as well.

cheers

steve

Steve, are you seriously attacking me now and trying to make me seem less than you?  You can stop that right now. I'm very impressed by your knowledge and I bow to it, but it means nothing in what audio is really about.

Please go build something superior and let us listen to it.

The only thing that is really important is, how does it sound and how does it make you (me) feel?  I'm a violinist and I've solo'ed with orchestras, I've been an orchestra director and music educator, and I'm an inventor with 3 patents awarded to me in the area of sound and acoustics. I have degrees in music performance and pedagogy, performance, and computer science.  I know what music is supposed to sound like and how I want to feel from my music. This is the only thing in audio that counts.

You don't have the right to try to make me or anyone else less than you. Be respectful, work and play well with others.

Jeeeeesssshhhhhh

Gary

« Last Edit: September 07, 2018, 02:57:51 PM by gander »
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Offline steve

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Re: How important is Power Supply Design?
« Reply #27 on: September 07, 2018, 02:53:30 PM »
Is there a way to test these diverging opinions?
Nick

Sure, compare the two ideas by actually building each of them, and then measure and hear the differences.  I can't tell you how many times I have bought gear based on theory, and my ears were often disappointed.

Gary

Gary, first, these are not theories, but laws. So what happened that the laws failed you? The answer is it was not the laws, but the amateurs who failed you. Don't blame the laws.

Secondly, disappointed in what? Designs that did not sound right? Not surprising since most designers either don't the laws, or follow the laws, especially diyers. And some large companies either don't understand the laws, or they don't want you to understand. Marketing and shilling is big business. 

For instance, capacitors have ESR, DA, and inductance problems. So whose capacitors are accurate? Well, every manufacturer claims his is. So who is right? Well, if you read some forums strings, and diyers, either one of two opinions exist.

1. All capacitors sound the same. Surprise, your component does not sound right (although junk capacitors were used).

2. We tested different brands and found, X, brand was the best. Problem is, they tested wrong, so the best, most accurate capacitor, Y, became extinct, because Y was judged bad by incompetents.

True example. X capacitor was judged to be better than Y because Y was bright sounding in the circuit. But the problem was the value of the capactors tested were too small of value.

Why? Because years ago, SETs guys had problems with overloading their small amplifiers and a burp would be heard. We can eliminate the burp by using a smaller capacitor. (Of course, the flat frequency response won't be flat.

They would use 0,47uf, 0,82uf coupling capacitors (tube circuits), so no burp and more prominent midrange. But it often sounded thin. But X capacitor sounded better because it was designed to sound more full, for a given value. So Y capacitor went into the bin, and became extinct.

I have tested many brands, and the most accurate sounding capacitor (for less than $30.00) is now extinct. All the other inferior caps are still being sold.

Improper testing, and improper size by diyers and others led to the state we are now in. It is all about money and looks, not sound.

So that is why theory has a bad reputation. Of course, many if not most make up theory to SELL their products. And unfortunately, many if not most either don't follow the laws of electronics, or their marketing theory doesn't follow the laws of electronics.

But the laws are still in force and they do work. That includes parts quality as well.

cheers

steve

Steve, are you seriously attacking me now and trying to make me seem less than you?  You can stop that right now. I'm very impressed by your knowledge and I bow to it.
Please go build something superior and let us listen to it - that is the only thing that is really important. How does it sound to you and how does it make you feel?

Jeeeeesssshhhhhh

Gary

I was simply giving a history lesson to the public, and how the marketers/ less qualified designers work. Theories are theories, and laws are laws. You got cheated Gary. I guess I could have simply stated such, so my apologies and I restructured my previous post.

My apologies.

cheers

steve
« Last Edit: September 07, 2018, 02:58:57 PM by steve »
Steve Sammet (retired, owner, SAS Audio Labs)
"V" Very Low Capacitance ICs, 40pf 1 meter
SAS Audio Labs Test Phono Stage
SAS Audio 11A Tube Reference Preamplifier
SAS Audio Labs 25 W Triode Reference Monoblocks
2 way test Spkrs, 28 - 20khz  -3db (28hz)

Offline gander

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Re: How important is Power Supply Design?
« Reply #28 on: September 07, 2018, 02:59:02 PM »
Is there a way to test these diverging opinions?
Nick

Sure, compare the two ideas by actually building each of them, and then measure and hear the differences.  I can't tell you how many times I have bought gear based on theory, and my ears were often disappointed.

Gary

Gary, first, these are not theories, but laws. So what happened that the laws failed you? The answer is it was not the laws, but the amateurs who failed you. Don't blame the laws.

Secondly, disappointed in what? Designs that did not sound right? Not surprising since most designers either don't the laws, or follow the laws, especially diyers. And some large companies either don't understand the laws, or they don't want you to understand. Marketing and shilling is big business. 

For instance, capacitors have ESR, DA, and inductance problems. So whose capacitors are accurate? Well, every manufacturer claims his is. So who is right? Well, if you read some forums strings, and diyers, either one of two opinions exist.

1. All capacitors sound the same. Surprise, your component does not sound right (although junk capacitors were used).

2. We tested different brands and found, X, brand was the best. Problem is, they tested wrong, so the best, most accurate capacitor, Y, became extinct, because Y was judged bad by incompetents.

True example. X capacitor was judged to be better than Y because Y was bright sounding in the circuit. But the problem was the value of the capactors tested were too small of value.

Why? Because years ago, SETs guys had problems with overloading their small amplifiers and a burp would be heard. We can eliminate the burp by using a smaller capacitor. (Of course, the flat frequency response won't be flat.

They would use 0,47uf, 0,82uf coupling capacitors (tube circuits), so no burp and more prominent midrange. But it often sounded thin. But X capacitor sounded better because it was designed to sound more full, for a given value. So Y capacitor went into the bin, and became extinct.

I have tested many brands, and the most accurate sounding capacitor (for less than $30.00) is now extinct. All the other inferior caps are still being sold.

Improper testing, and improper size by diyers and others led to the state we are now in. It is all about money and looks, not sound.

So that is why theory has a bad reputation. Of course, many if not most make up theory to SELL their products. And unfortunately, many if not most either don't follow the laws of electronics, or their marketing theory doesn't follow the laws of electronics.

But the laws are still in force and they do work. That includes parts quality as well.

cheers

steve

Steve, are you seriously attacking me now and trying to make me seem less than you?  You can stop that right now. I'm very impressed by your knowledge and I bow to it.
Please go build something superior and let us listen to it - that is the only thing that is really important. How does it sound to you and how does it make you feel?

Jeeeeesssshhhhhh

Gary

I was simply giving a history lesson to the public, and how the marketers/ less qualified designers work. Theories are theories, and laws are laws. I guess I could have simply stated such, so my apologies.

My apologies.

cheers

steve

You're fired from my classroom, if you were teaching for me.
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Offline steve

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Re: How important is Power Supply Design?
« Reply #29 on: September 07, 2018, 03:13:53 PM »
Is there a way to test these diverging opinions?
Nick

Sure, compare the two ideas by actually building each of them, and then measure and hear the differences.  I can't tell you how many times I have bought gear based on theory, and my ears were often disappointed.

Gary

Gary, first, these are not theories, but laws. So what happened that the laws failed you? The answer is it was not the laws, but the amateurs who failed you. Don't blame the laws.

Secondly, disappointed in what? Designs that did not sound right? Not surprising since most designers either don't the laws, or follow the laws, especially diyers. And some large companies either don't understand the laws, or they don't want you to understand. Marketing and shilling is big business. 

For instance, capacitors have ESR, DA, and inductance problems. So whose capacitors are accurate? Well, every manufacturer claims his is. So who is right? Well, if you read some forums strings, and diyers, either one of two opinions exist.

1. All capacitors sound the same. Surprise, your component does not sound right (although junk capacitors were used).

2. We tested different brands and found, X, brand was the best. Problem is, they tested wrong, so the best, most accurate capacitor, Y, became extinct, because Y was judged bad by incompetents.

True example. X capacitor was judged to be better than Y because Y was bright sounding in the circuit. But the problem was the value of the capactors tested were too small of value.

Why? Because years ago, SETs guys had problems with overloading their small amplifiers and a burp would be heard. We can eliminate the burp by using a smaller capacitor. (Of course, the flat frequency response won't be flat.

They would use 0,47uf, 0,82uf coupling capacitors (tube circuits), so no burp and more prominent midrange. But it often sounded thin. But X capacitor sounded better because it was designed to sound more full, for a given value. So Y capacitor went into the bin, and became extinct.

I have tested many brands, and the most accurate sounding capacitor (for less than $30.00) is now extinct. All the other inferior caps are still being sold.

Improper testing, and improper size by diyers and others led to the state we are now in. It is all about money and looks, not sound.

So that is why theory has a bad reputation. Of course, many if not most make up theory to SELL their products. And unfortunately, many if not most either don't follow the laws of electronics, or their marketing theory doesn't follow the laws of electronics.

But the laws are still in force and they do work. That includes parts quality as well.

cheers

steve

Steve, are you seriously attacking me now and trying to make me seem less than you?  You can stop that right now. I'm very impressed by your knowledge and I bow to it.
Please go build something superior and let us listen to it - that is the only thing that is really important. How does it sound to you and how does it make you feel?

Gary

I was simply giving a history lesson to the public, and how the marketers/ less qualified designers work. Theories are theories, and laws are laws. I guess I could have simply stated such, so my apologies.

My apologies.

cheers

steve

You're fired from my classroom, if you were teaching for me.

First of all, this is my string, I started it, and my classroom, not yours. So why did you post here if you don't' like electronic laws or my white paper? It would not be to support your fellow diyer folsom, would it?

A decoupling power supply capacitor does handle musical signal content and has reactance, and also alters the frequency response vs frequency. That is the law, not theory.

I even edited my last post to differentiate between what I wanted the public to understand vs the small amount replying to you.
And I even apologized to you.

I do have one advantage in that I have applied the laws to my system and been able to compare with many other systems, over the years and even decades, that others have not.

Now this come back from you.... If you don't like science laws or my scientific white paper, then don't post.... and exit this string. I was nice enough to reply, and give you reasons why theory did not satisfy what you heard/experienced.

cheers

steve
« Last Edit: September 07, 2018, 04:54:02 PM by steve »
Steve Sammet (retired, owner, SAS Audio Labs)
"V" Very Low Capacitance ICs, 40pf 1 meter
SAS Audio Labs Test Phono Stage
SAS Audio 11A Tube Reference Preamplifier
SAS Audio Labs 25 W Triode Reference Monoblocks
2 way test Spkrs, 28 - 20khz  -3db (28hz)