[bigshot]

I can literally create an an amplifier with unmeasurable distortion and very low output impedance using differential error correction for a few dollars. If it was that simple this website would not exist.

Oh heavens! You don't want to get into the subject of why this website exists! It has very little at all to do with how things sound!

I have less than no interest in wasting hours of my time gathering data to prove my point to people on the internet for zero gain. I'm not interested in getting in extensive and petty arguments nor do I want to repeat things I've said. You can argue on the internet while I actually build and design.

You say this after hours of doing just that?! Why are you here at all?

(he'll be back. he seems to need our validation.)

 

[Philosobyte]

I wouldn't want to do what Schiit did and be in a frantic rush for designs and resort to antiquated topologies (not that there's anything necessarily wrong with that).

If you're calling a high-performing topology antiquated, then what about the wheel? If you try to replace the wheels on any modern car with anything that's not a wheel, it will invariably drive worse. But since wheels were invented thousands of years ago, they're antiquated. Right?

You also need a source for Schiit being in a "frantic rush" when they used an "antiquated" topology like the circlotron.
I have a source to the contrary - Jason's chapter on the Mjolnir and circlotron shows that they chose the circlotron as the best option after careful consideration of all of their options. They also had to overcome several engineering hurdles to get it to work, so they clearly weren't being lazy (unless you think they're lying, at which point I would give up). https://www.head-fi.org/threads/sch...orlds-most-improbable-start-up.701900/page-73

Since I love you so much, I took the time to cut some of the relevant parts here in case you don't want to parse through the entire chapter. I used ellipses to indicate a cut.

Chapter 17:

...
...
Balanced disadvantages:

1. More parts, more complexity (except for maybe circlotrons)

...
...
Onto the Circlotron

So why was Mjolnir a circlotron from the start? After all, there are plenty of other ways to do a balanced amp... They’re simple, high-performance, and neatly sidestep some of the problems inherent in other amplifier topologies (more on this later.)

Back as Sumo, we made circlotron-style amplifiers, but they were Jim Bongiorno’s designs. I’d never designed a circlotron amp. And yet they kept drawing me back in. First, because the topology is so different than anything else out there. When you first look at it, your natural reaction is “how the hell could that ever work?” Then, when you understand the principle behind it, you think, “wow, that’s really elegant. Why aren’t there more of these?”
...

Some Solid-State Amplifier Topologies
...
CSPP/Circlotron. Note that none of the topologies discussed above, except supersymmetry, is inherently balanced. Now we get to the Cross Shunt Push Pull amp, which is a very old topology (from the 1950s, google “Circlotron patent” for more info. First applied in tube amplifiers and named “Circlotron” by Electrovoice, the CSPP topology at first looks like a mistake. Oversimplifying, all of the topologies measured above use the output devices as, well, “valves” that control the flow of current from one or two voltage rails to a single output node. The CSPP uses these devices to “unbalance” the flow of current from two cross-coupled power supplies to two output nodes, one positive and one negative. Thus, it’s an inherently balanced design. It will never be anything other than a balanced design. And you will never get anything out of it except for balanced output (more on that later.)
...
So, we went with a relatively old power amp topology because it was inherently balanced—and also very simple. It uses only N-channel devices (or only P-channel devices, if you swing that way), so there’s no worry about the N-channel and P-channel devices being mismatched. It does, however, require a complex power supply—two separate non-ground-referenced power supply rails for each channel. If you look at the CSPP transformer on the Mjolnir (the larger one), you’ll see it has about a billion output pins. That’s why.
...
So where does that take us? We have BJTs, JFETs, MOSFETs, SITs, and op-amps to play with. We don’t have anything against any of those devices. But for voltage amplification, we tend to like JFETs and BJTs, in that order, and we tend to like MOSFETS and BJTs for output devices, in that order.

Why the hate for BJTs? Well, it’s not really hate. Just caution. Current-driven devices are fine, but they need to have a little extra work to make sure you have enough current to drive them, even when they’re working hard and beta is drooping. And you have to watch their safe operating area and thermal characteristics a bit more.

What we ended up doing in the early Mjolnir design (and we’re talking breadboards here, not PC boards) was trying two different topologies:

• High-voltage JFET front end and MOSFET output with no overall feedback.
• JFET front end, BJT VAS stage, and MOSFET output, with local feedback around the VAS and output stage only.

We focused on these two topologies because both were simple, and both sidestepped the “different gain per phase” problem inherent in balanced amps that are driven single-ended.

What do I mean by this? I mean, if you drive a differential amp with overall feedback with a balanced signal, it produces a balanced output. 1V in, gain of 10 = 10V on either side.

But, if you drive a differential amp with overall feedback with a single-ended signal, it produces an unbalanced output: 1V in, gain of 10 = 10V on one phase, 11V on the other.

Huh?

Yep. Look it up in an opamp cookbook. You’ll see the different gains per phase and ways to compensate for them.

However, since we wanted to have an amp with both balanced and single-ended input, we wanted to avoid having different gains per phase. That would mean we’d have to switch the feedback resistors (say, with relays) to compensate if a single-ended input was used. No, thanks. I didn’t really want to have 10 relays inside a Mjolnir. This was supposed to be a simple, no-frills, performance-is-everything kinda amp.

What was interesting about those two topologies was how closely they measured. We found that by using 95V rails and a special high-voltage JFET (which I think we own the world stock of), we could get very, very close to the measured performance of the amp with the VAS stage—without any feedback.

This made for a very simple amplifier. The path was set. Mjolnir would be a no-overall-feedback, single-stage amp design.
...

Early Adventures with Mjolnir

“Circlotron?” Mike asked doubtfully. “Isn’t that something that only 6 people in the world know how to do, and even then they have to chant incantations and swing dead chickens over their heads to make them work?”

“No, they really aren’t that bad—“ I began.

“Famous last words,” Mike cut me off.

“They’re actually really simple—“

“Except for the keeping it balanced problem, the voodoo transformer, the eight thousand voltage rails, the weird in-the-air outputs, and making sure some idiot doesn’t ground the negative output and blow it up problem, you mean.”

“Well, yeah, but—“

“But you’re gonna do it anyway.”

 

[coinmaster]

You say this after hours of doing just that?! Why are you here at all?

(he'll be back. he seems to need our validation.)

If you put time into reading my posts you would know why I was still here. No need to be an A$$hole.

If you're calling a high-performing topology antiquated, then what about the wheel? If you try to replace the wheels on any modern car with anything that's not a wheel, it will invariably drive worse. But since wheels were invented thousands of years ago, they're antiquated. Right?

It is antiquated.....saying it isn't would be a lie. Notice how I put in brackets saying that's not a bad thing.
Careful, the fanboy in you seems to be leaking out.

My preference for new topologies has nothing to do with performance per se. It's about what Schiit refers to as "not invented here" syndrome (in other words "if we didn't invent it, we don't want it") I have this syndome pretty bad.

You also need a source for Schiit being in a "frantic rush" when they used an "antiquated" topology like the circlotron.

They said it in their journal at various points. They were under pressure to come up with designs even with their "not invented here" syndrome and had to find a known topology that would work. The Lin amp is an example.

Like I said, nothing wrong with that. It's just not the way I would do things. If there was a known topology that melted my brain with goodness I would be all for it but since I've yet to find one like that I'd rather stray off the beaten path where it's more fun and adventurous. Personally I think the circlotron is boring, why? I don't know, I can't quite put my finger on it. Maybe it's just too "normal" for me (relatively speaking) I'm sure I could make come crazy variation of a circlotron but I will save that for some other time maybe, I have my own circuits to deal with for the time being.

Since I love you so much

Why thank you, I was beginning to feel unwelcome.
Eventually I nee to get back to what I was doing though, ugh

 

[pinnahertz]

If you're into product development and haven't done your market analysis first, you've hobbled your chances severely.

Please do not take this as an insult, that's not how I mean it: what you have outlined so far is a hobby, or flea market level part time business at best. You are taking some big steps out of sequence.

I strongly suggest reading "The 22 Immutable Laws of Marketing" by Reis and Trout. It's not going to teach you enough about marketing to make your business successful, but will shed some light in the area of "you don't know what you don't know", which is where we always get bitten the hardest. And that's not a book about running a manufacturing business, which is the other big blind spot most startups have.

Aside from what you think you have to sell, and your admirable value of philosophy, I can assure you, you have some unpleasant surprises ahead that cannot be avoided without a business plan and the involvement of others who specialize in your blind areas.

You're choosing to take the uphill muddy dirt road here, and while you can still get to the top of the hill, wouldn't it be better in the road paved with the knowledge and experience of others? Even if you don't care if your backpack is full of cash?

 

[coinmaster]

Please do not take this as an insult, that's not how I mean it: what you have outlined so far is a hobby, or flea market level part time business at best.

Yeah I'm keeping my expectations at that level. I would be satisfied if I sold 1 amplifier per month.

My current "flagship" product would cost about $260 to make if I'm careful. John Broskie and others told me that I should run at a 4X profit margin. Seems logical when I think about the other costs of business.
Not sure If it is smart or not to sell @ near a grand though even though it does seem to be the going rate for high-end "budget" amps of similar size. Little Dot Mk6 comes to mind.

You're choosing to take the uphill muddy dirt road here, and while you can still get to the top of the hill, wouldn't it be better in the road paved with the knowledge and experience of others?

Well yeah, but I know of no such people

Even if you don't care if your backpack is full of cash?

I'm not really looking to "get rich" If I can just support myself I would be happy.

 

[Philosobyte]

It is antiquated.....saying it isn't would be a lie. Notice how I put in brackets saying that's not a bad thing.

Yes, I know you said it's not a bad thing. I just wanted to confirm whether or not you'd call a wheel antiquated.

Careful, the fanboy in you seems to be leaking out.

Please do not throw personal insults.

My preference for new topologies has nothing to do with performance per se. It's about what Schiit refers to as "not invented here" syndrome (in other words "if we didn't invent it, we don't want it") I have this syndome pretty bad.

They said it in their journal at various points. They were under pressure to come up with designs even with their "not invented here" syndrome and had to find a known topology that would work. The Lin amp is an example.

Not invented here syndrome had nothing to do with it (most of Schiit's not invented here is with DACs because they're designed by Mike). Remember, the only Lin amp they did was the Magni. When they were designing the Magni, they were considering other known topologies like CFA. If they'd thought of using a Lin amp they would have used it earlier; it had nothing to do with rushing or being frantic.


Also you just contradicted yourself. You say your preference for new topologies has nothing to do with performance, yet you say if there were a known topology that melted your brain with goodness you would be all for it.

You also seem to be of the impression that any topology sounds the same no matter the implementation. I'm not an EE, so I would like someone else to clarify, but I'd be highly surprised if that were true. I've been under the impression that it's the implementation, not the topology, that matters.

 

[coinmaster]

Yes, I know you said it's not a bad thing. I just wanted to confirm whether or not you'd call a wheel antiquated.

Very Still waiting on those flying cars.

Please do not throw personal insults.

I never mean anything as an insult. I'm just blunt, don't take offense. Some people can't stand me for that quality

Also you just contradicted yourself. You say your preference for new topologies has nothing to do with performance, yet you say if there were a known topology that melted your brain with goodness you would be all for it

If a specific topology "melted my brain with goodness" why would I need to care about performance any longer? Old topologies have known strengths and weaknesses. If they didn't impress me I'd rather move forward.

You also seem to be of the impression that any topology sounds the same no matter the implementation

Nah, the same topology can sound like 1000 different things depending on how it's implemented. But topologies do have inherent strengths and weaknesses. None is perfect (although some are pretty darn close).
Keep in mind when choosing a design you need to start with topology first. Implementation may be the more important factor (or not, depending on the situation), but topology is the groundwork for anything you apply afterword.

 

[sonitus mirus]

I'm a bit of a skeptic, which is a healthy attribute to have in this hobby. Anyone stating that they build better amps because they are an EE with design secrets and that refuses to provide any evidence demonstrating this is even remotely factual does not employ my confidence in their products.

It is silly. We have not even breached the idea of blind listening tests since we have not been provided anything that might suggest the listening test would be anything other than a ridiculous folly. I can't believe people fall for this type of nonsense, but the proof is in the sales of crazy audiophile products.

 

[coinmaster]

I'm a bit of a skeptic, which is a healthy attribute to have in this hobby

Or in life.

Anyone stating that they build better amps because they are an EE with design secrets

Okay this is getting silly. Nothing I said was a secret. I do have my own tricks but what I said was just fundamental audio design. If you think what I said was "magic" then you simply aren't versed enough in audio design theory, which is why I said go to diyaudio.com or use google to learn more about audio EE. There is too much to say for me to explain in a thread on random request. I simply confirmed what I learned through my experiments and use it as a guideline as long as it provides improvements.
The biggest faults in this industry seem to be ignorance and a lack of creativity, without a doubt.
To think people on the "audio science" forum think anything other than THD measurements is "audio voodoo"...I expected too much.

 

[bigshot]

There are lots of audibly transparent amps. Every one I've owned since 1975 has been audibly transparent. If you want to split atoms and create something that measures better, it's still going to sound the same. A gold spoon is just as good to eat soup with as a stainless steel one. My skepticism comes in when someone starts saying that .00001% THD is audible. Yes, some kinds of distortion are more audible than others, and manufacturer's specs aren't to be trusted, But there's a threshold somewhere where it doesn't make any difference any more. I don't think it's even an issue, because I think most solid state amps sound perfect.

Now if you want to talk about *adding distortion* to make something sound better, I will listen. I believe that DSPs are the future of high end audio, not more "purity". I'll happily listen to your theories on that. But I don't want that hard wired into my amp. I want it adjustable and as a plugin at the end of the chain, just like an equalizer. Salt and pepper to taste.

 

[coinmaster]

there are lots of audibly transparent amps. Every one I've owned since 1975 has been audibly transparent. If you want to split atoms and create something that measures better, it's still going to sound the same. A gold spoon is just as good to eat soup with as a stainless steel one. My skepticism comes in when someone starts saying that .00001% THD is audible

Yes, in my experience these amps sound boring and unrealistic. My benchmark for sound is how well the headphone/speakers confuse my brain into thinking the music is real in 3d space. Also I enjoy sound that is both "euphonic" and " accurate" a rare combination.
Also like I said there's more to how it sounds through the coil than just the THD figure. Like MrCurwen said, it's like diagnosing human health. You can't use only aspect to determine, there's more to it than that in practice.

Now if you want to talk about *adding distortion* to make something sound better, I will listen. I believe that DSPs are the future of high end audio, not more "purity". I'll happily listen to your theories on that.

I do indeed think adding "proper" distortion is a good way to go. I don't know too much on the possibilities DSPs offer that make you think they are the future. If you'd like to enlighten me.

But I don't want that hard wired into my amp. I want it adjustable and as a plugin at the end of the chain, just like an equalizer. Salt and pepper to taste.

I have my own method of doing this. I question the sonic integrity of such using an digital sound shaping for this. My ongoing research on DAC design makes me skeptical of such DSP audio shaping. Perhaps you can enlighten me on your own experiences.

 

[pinnahertz]

Yeah I'm keeping my expectations at that level. I would be satisfied if I sold 1 amplifier per month.

This ^^^^
And then this....

My current "flagship" product would cost about $260 to make if I'm careful. John Broskie and others told me that I should run at a 4X profit margin. Seems logical when I think about the other costs of business.

Don’t add up to this:

If I can just support myself I would be happy.

...unless you can live AND run a one-man business bringing in $740/month before expenses.

You are a match to the hobby/crafting model. Crafters make “kitchen witches” and sell them at craft fairs for a negative net. They may make the best kitchen witch on earth and have fun doing it but they all have another source of income to live on and support their hobby. You’d do better supporting yourself flipping burgers for minimum wage and never making more than one amp for yourself.

If you really have a EE (I realize you never actually said you did) you do have the potential to make substantially more than minimum wage with that degree doing any number of things, all the while picking up contacts and experience in the world of product development and manufacturing. But having the degree is not essential for a successful product and company. In fact, it’s likely to get in the way.

Nobody ever gets outside funding for a hobby. There is funding for legitimate startups with sold business models. But you will need proof of concept which, in this case, would be most valuable in the form of a series of controlled listening tests, first as an ABX/DBT with your closest competing product followed by a spastical analysis of listener preference. Show your product solidly wins listener favor, has a competitive place in the market (that means a 3-fold improvement over existing products in the category), and you’ll find all the funding you need for a real business.

Otherwise all you have here is MQA without the higher profile, recognized names, and financial backing. They have never supplied any proof of concept, and routinely get ripped to shreds, even with funding, and will eventually fail completely.

BTW, you won’t get anyone to review your product if it’s not a real, manufactured product that their audience can go and buy their own copy of. You’re up against established product with high value (being made by slave labor off-shore, etc, etc..) as a guy making an amp on his kitchen table. Think of the reality of this, then see if what you really should be doing is more product development. You can get your funding with a single demonstrably workin prototype, then get paid to beat the thing down to the real production version.

You keep claiming you “don’t know these people”. You should make it your business to find them. They aren’t going to find you, but they are out there.

You won’t learn any of this studying EE, though. See what I mean? Your project is probably 15% EE at most.

 

[Niouke]

I must say that my mind was already made up when I posted this thread, to me all well conceived amps sound the same and are audibly transparent, and nobody posted proof that this isn't true yet, although I am curious of the distortion vs freq graph. Here are a few statements I found on the subject:

3. Under normal conditions, virtually all audio amplifiers/receivers sound the same (sans EQ). They do not have their own sonic signature that must be carefully paired with speakers.

• “They may sound different if they are used at high volume levels as they approach the limits of their output ratings, when the amplifiers’ distortion is rising and nearing the clipping point. However, if two different transistor amplifiers have the same smooth, linear frequency response, low distortion, and are operated within their output ratings, then they will tend to sound identical until they are called upon to produce great quantities of clean, unclipped power.” – 10 Things about Audio Amplifiers You’ve Always Wanted to Know @ Audioholics
• “Then I started to hear about some convincing blind tests and finally conducted my own. I was stunned at the results. I couldn’t tell a $300 amp from a $3000 in the store I was working at. Neither could anyone else who worked there. It was a major blow to my audio belief system.” – Blind Listening Tests & Amplifiers @ DIY Audio forums
• “His challenge is an offer of $10,000 of his own money to anyone who could identify which of two amplifiers was which, by listening only, under a set of rules that he conceived to make sure they both measure ‘good enough’ and are set up the same. Reports are that thousands of people have taken the test, and none has passed the test. Nobody has been able to show an audible difference between two amps under the test rules.” – Richard Clark $10,000 Amplifier Challenge FAQ by Tom Morrow
• “Any amplifier, regardless of topology, can be treated as a ‘black box’ for the purpose of listening comparisons. If amplifiers A and B both have flat frequency response, low noise floor, reasonably low distortion, high input impedance, low output impedance, and are not clipped, they will be indistinguishable in sound at matched levels no matter what’s inside them.” – Obsession with Amplifiers @ The Audio Critic
• “The loudspeaker will determine how your music system sounds. Not the amplifier, not the preamplifier, not the CD or DVD player, nothing but the loudspeaker. Speakers, even the finest, are far less accurate in terms of output compared to input than any of those other components. The speaker will be invariably the weakest link in the chain, the link that limits the quality of sound reproduction.” – A Note About Loudspeakers @ The Audio Critic
• “But for now, the evidence would seem to suggest that distinctive amplifier sounds, if they exist at all, are so minute that they form a poor basis for choosing one amplifier over another. Certainly there are still differences between amps, but we are unlikely to hear them.” – Do All Amplifiers Sound the Same? @ Stereo Review
• “No one has ever produced a scientifically controlled listening test showing that well-designed amplifiers (flat frequency response, no clipping), preamplifiers, integrated circuits, and speaker wires (16-guage and bigger) have the slightest effect on the sound being produced.” – Can You Trust Your Ears? by Tom Nousaine
• “An apparently insurmountable objection to the existence of non-measurable amplifier quirks is that recorded sound of almost any pedigree has passed through a complex mixing console at least once; prominent parts like vocals or lead guitar will almost certainly have passed through at least twice, once for recording and once at mix-down. More significantly, it must have passed through the potential quality-bottleneck of an analogue tape machine or more likely the A-D converters of digital equipment. In its long path from here to ear the audio passes through at least a hundred op-amps, dozens of connectors and several hundred meters of ordinary screened cable. If mystical degradations can occur, it defies reason to insist that those introduced by the last 1% of the path are the critical ones.” – Science and Subjectivism in Audio by Douglas Self
• “Now that I have mentioned these various types of distortion, I think it’s safe to say a well designed amplifier will reduce these effects to the point of inaudibility. Because of this, and because of the conclusions from blind listening tests, it’s not clear why some people hear differences in how amplifiers sound.” – Amplifier FAQ @ AVSForum

source: https://numeralnine.wordpress.com/2013/10/09/a-brief-guide-to-audio-for-the-skeptical-consumer/

 

[MrCurwen]

Niouke you're making a bold claim, so I will examine the words used very closely. I understand that normal communication doesn't allow endless caveats; however some distinctions need to be made in my opinion.

3. Under normal conditions, virtually all audio amplifiers/receivers sound the same (sans EQ). They do not have their own sonic signature that must be carefully paired with speakers.

As written, absolutely not. Simply an absurd statement. I realise this is not what you (probably) meant to propose, so let's unpack the statement.

A home listening audio amplifier made in the 1960's is most certainly going to sound different than one made in the 1970's or 2010's. Not to mention from the 1930's, say the Loftin-White or similar.

Let's take an open loop tube amp with a basic topology from the retro days, but with a lot of modern stuff added in. Let's say LED cathode bias and stuff like that. Nothing drasticly altering the topology. It is made in the same decade as the 700 eur decent quality receiver bought at a big box store. These amps are in effect contemporaries, however they will most certainly sound different.

Your statement, if interpreted in good faith, is talking about gNFB amps, more specifically amps utilizing a lot of gNFB. By any knowledge of the basics of electronics, gNFB is going to 'flatten' almost every difference. (Also it is going to flatten the sound, but that is my subjective opinion.)

So; amps that use a lot of gNFB are going to sound identical.

This is a truism, a tautology.

However what about the amps that do no utilize a lot of gNFB, or that are open loop? Are they not in the picture at all, or are they considered as being of a quality not worth considering?

I'm an open loop guy who dislikes distortion, as I explained in my previous message here. I don't enjoy "tube sound" in my HIFI yet I detest gNFB sound.

Is my amp included in that blanket statement?

(For the purposes of this discussion "my amp" can be considered an abstract thought experiment since this thread is not about schems but about concepts, but for those more interested in practicalities look at Sonic's thread: https://www.head-fi.org/threads/modern-balanced-tube-amp-build.852879/ )

However, if two different transistor amplifiers have the same smooth, linear frequency response, low distortion, and are operated within their output ratings, then they will tend to sound identical until they are called upon to produce great quantities of clean, unclipped power

Yes, SS amps which by necessity utilize huge amounts of gNFB. gNFB will sound like gNFB.

“The loudspeaker will determine how your music system sounds. Not the amplifier, not the preamplifier, not the CD or DVD player, nothing but the loudspeaker. Speakers, even the finest, are far less accurate in terms of output compared to input than any of those other components. The speaker will be invariably the weakest link in the chain, the link that limits the quality of sound reproduction.”

I do somewhat agree, but not to the level proposed in the quote. There is a lot to be said about focusing on the bottleneck. However from working with guitar tube amps a lot, I understand very well what "distortion on distortion" is and sounds like. There is a difference in final output depending on how gradually you introduce distortion, and what kind of distortion to introduce at what point. The audio chain does in my opinion operate somewhat as a whole. That said, if you have crappy speakers, it's not going to matter a lot if you shave off some distortion from the amp.

“No one has ever produced a scientifically controlled listening test showing that well-designed amplifiers (flat frequency response, no clipping), preamplifiers, integrated circuits, and speaker wires (16-guage and bigger) have the slightest effect on the sound being produced.” – Can You Trust Your Ears? by Tom Nousaine

'Scientifically' is one of those potentially weaselwords that instantly bring up my skepticism senses.

Humans bred animals and crops millenia before anybody found out about DNA and genes even existing. And nowadays that we know about DNA, somebody can say "show me the exact gene that produces X in this species", and after you inevitably cannot (at least yet), following the same logic of SCIENTIFIC PROOF the sophist can claim "trait X is not heritable in that species" even though it clearly is.

The fact that tests have not proved something proves that tests have not proven something. This is not a claim of fact ("it is not so"), but rather an indicator among others. This is not to say science is all bunk, but rather to understand it's limitations.

To bring it closer to topic at hand: which listening tests are scientific and which are not? I have a lot of logged listening test hours, by my ears. Are they scientific?

Wavebourn used his cats (and house guests) as scientific test subjects. If the cat or the houseguests arriving at the house in another room thought the sound was a real instrument being played, his amp was realistic. Is this scientific? If not, why not?

An apparently insurmountable objection to the existence of non-measurable amplifier quirks is that recorded sound of almost any pedigree has passed through a complex mixing console at least once; prominent parts like vocals or lead guitar will almost certainly have passed through at least twice, once for recording and once at mix-down. More significantly, it must have passed through the potential quality-bottleneck of an analogue tape machine or more likely the A-D converters of digital equipment. In its long path from here to ear the audio passes through at least a hundred op-amps, dozens of connectors and several hundred meters of ordinary screened cable. If mystical degradations can occur, it defies reason to insist that those introduced by the last 1% of the path are the critical ones

This is the "distortion on distortion" thing again. In my technical and listening opinion it is not at all insignificant to add distortion to an already distorted sound.

Think about an old recording that has let's say 5% THD, mostly second and third. Made in the late 1930's for example.

So you might think this recording is already so distorted in comparison to the acoustic performance it was captured from, that it doesn't matter whether the amp replaying it is producing 1% THD or 0.01% THD.

Completely wrong in my opinion.

Basic level understanding of wave physics (sound is just a waveform, whether electric or air pressure) tells us that when two waveforms are added, the resulting intermodulation products are of higher order than either of the original waves contained. The bigger the 'new' wave (added by the amp), the bigger the 7H 8H 9H components that are produced by the intermodulation. This is the very worst kind of distortion there is.

This means that if you play your bad recording thru a bad amp, the results is significantly worse than if you play it thru a good amp. This same effect in my opinion makes all the 'distortion shaping' and such nonsense a very bad idea.

So no matter what happens in the studio, the way you play it back matters a lot.

I personally found that the most retro stuff I listen to, jazz and blues for 1930 to 1950, became the most alive after listened thru an open loop low THD amp. SS amps don't have this effect and after thinking about the intermodulation effect and knowing the THD spectra of gNFB amps this is not a mystery.

 

[pinnahertz]

Niouke you're making a bold claim, so I will examine the words used very closely. I understand that normal communication doesn't allow endless caveats; however some distinctions need to be made in my opinion.



As written, absolutely not. Simply an absurd statement. I realise this is not what you (probably) meant to propose, so let's unpack the statement.

A home listening audio amplifier made in the 1960's is most certainly going to sound different than one made in the 1970's or 2010's. Not to mention from the 1930's, say the Loftin-White or similar.

Let's take an open loop tube amp with a basic topology from the retro days, but with a lot of modern stuff added in. Let's say LED cathode bias and stuff like that. Nothing drasticly altering the topology. It is made in the same decade as the 700 eur decent quality receiver bought at a big box store. These amps are in effect contemporaries, however they will most certainly sound different.

Your statement, if interpreted in good faith, is talking about gNFB amps, more specifically amps utilizing a lot of gNFB. By any knowledge of the basics of electronics, gNFB is going to 'flatten' almost every difference. (Also it is going to flatten the sound, but that is my subjective opinion.)

So; amps that use a lot of gNFB are going to sound identical.

This is a truism, a tautology.

However what about the amps that do no utilize a lot of gNFB, or that are open loop? Are they not in the picture at all, or are they considered as being of a quality not worth considering?

I'm an open loop guy who dislikes distortion, as I explained in my previous message here. I don't enjoy "tube sound" in my HIFI yet I detest gNFB sound.

Is my amp included in that blanket statement?

(For the purposes of this discussion "my amp" can be considered an abstract thought experiment since this thread is not about schems but about concepts, but for those more interested in practicalities look at Sonic's thread: https://www.head-fi.org/threads/modern-balanced-tube-amp-build.852879/ )

I don't completely disagree that open loop can sound different from gNFB, but which one represents the input signal with the best accuracy when working into a real world complex load?

I do somewhat agree, but not to the level proposed in the quote. There is a lot to be said about focusing on the bottleneck. 1. However from working with guitar tube amps a lot, I understand very well what "distortion on distortion" is and sounds like. There is a difference in final output depending on how gradually you introduce distortion, and what kind of distortion to introduce at what point. 2. The audio chain does in my opinion operate somewhat as a whole. That said, if you have crappy speakers, it's not going to matter a lot if you shave off some distortion from the amp.

Two problems here:
1. An instrument amp definitely becomes part of the total instrument sound, and is often operated well into an area of clearly audible distortion. There is no parallel in hifi audio for this kind of operation or system.

2. Yes, the entire chain operates as a whole, but all speakers are crappy relative to an amp of any hifi design in every single aspect, FR, distortion, intermod, phase response, everything but noise. Speakers are the big problem, amp-speaker interface/interaction is next, then amp performance itself. The exceptions here would be how nonlinear the amp is, how far into nonlinear operation it is pushed, and the total spectral content that results. However, if operated in its linear range, and the amp replicates the input signal accurately, the speaker is the weak link by several orders of magnitude.

'Scientifically' is one of those potentially weaselwords that instantly bring up my skepticism senses.

Humans bred animals and crops millenia before anybody found out about DNA and genes even existing. And nowadays that we know about DNA, somebody can say "show me the exact gene that produces X in this species", and after you inevitably cannot (at least yet), following the same logic of SCIENTIFIC PROOF the sophist can claim "trait X is not heritable in that species" even though it clearly is.

The fact that tests have not proved something proves that tests have not proven something. This is not a claim of fact ("it is not so"), but rather an indicator among others. This is not to say science is all bunk, but rather to understand it's limitations.

To bring it closer to topic at hand: which listening tests are scientific and which are not? I have a lot of logged listening test hours, by my ears. Are they scientific?

No idea about your specific tests. When testing for the effect of something science dictates that all variables be considered and where possible brought under control. When testing for the audibility of something it is paramount to control all other sensory and psychological input to eliminate bias. Science has proven then significant impact of biases in many disciplines, including medicine. It's not insignificant at all. My bias is, when I hear "hours of listening tests" I expect they are fully sighted and thus biased and dismissible.

Wavebourn used his cats (and house guests) as scientific test subjects. If the cat or the houseguests arriving at the house in another room thought the sound was a real instrument being played, his amp was realistic. Is this scientific? If not, why not?

How did the cat input his observation data?

This is the "distortion on distortion" thing again. In my technical and listening opinion it is not at all insignificant to add distortion to an already distorted sound.

Agreed, the statement you referred to is naive. Many distortions (notably FR) are not masked by others in the chain, and might add (or not). Certain similar types of distortions occurring in multiple stages do add. Again, FR comes to mind. The HF rolloff of analog tape coupled with the HF rolloff of a tube amp driving a capacitive load coupled with the HF rolloff of a tweeter compound to a greater HF rolloff than any one part of that. Yes, I cherry picked the example, but it does happen. Other distortions caused by nonlinearities do not necessarily add (or subtract) from each other. In fact, under very specific conditions, it is even possible to pre-distort a signal entering a stage with known nonlinear distortion such that the result is less distorted. It's a very old technique, not usually found or required today. However, unintentional pre-distortion would be a near impossibility because it must be so precisely specific to work at all.

Think about an old recording that has let's say 5% THD, mostly second and third. Made in the late 1930's for example.

So you might think this recording is already so distorted in comparison to the acoustic performance it was captured from, that it doesn't matter whether the amp replaying it is producing 1% THD or 0.01% THD.

Completely wrong in my opinion.

It depends entirely on what makes up the 1%, but your 5% figure for the 1930s 78 record is low. And the 1% THD amp would be questionable in today's world, would definitely require much more information. Remember, a single figure THD spec is useless, it's a 3D data block with magnitude, frequency and resulting products as axis.

Basic level understanding of wave physics (sound is just a waveform, whether electric or air pressure) tells us that when two waveforms are added, the resulting intermodulation products are of higher order than either of the original waves contained. The bigger the 'new' wave (added by the amp), the bigger the 7H 8H 9H components that are produced by the intermodulation. This is the very worst kind of distortion there is.

Yes, but for intermodulation to be produced between two waveforms there must be a nonlinear element. Amps with better linearity produce less IMD. Generally, IMD and THD track each other, though. While IMD is much more obnoxious, there will also be measurably high THD in that system too.

This means that if you play your bad recording thru a bad amp, the results is significantly worse than if you play it thru a good amp. This same effect in my opinion makes all the 'distortion shaping' and such nonsense a very bad idea.

Generally agreed, but that's a very binary way to look at it.

So no matter what happens in the studio, the way you play it back matters a lot.

Sure, but past a certain point of performance the contribution of a component drops below the noise floor, and not longer matters at all.

I personally found that the most retro stuff I listen to, jazz and blues for 1930 to 1950, became the most alive after listened thru an open loop low THD amp. SS amps don't have this effect and after thinking about the intermodulation effect and knowing the THD spectra of gNFB amps this is not a mystery.

Interesting non-scientific subjective opinion. But you have causality confused, and you are ignoring an entire range of other issues that make those amps different, instead blaming intermod and THD. The full profile of an open loop amp vs a good SS amp with gNFB working into your specific load would need to be done to see what it is you are hearing. You also would need a DBT to confirm that your observations are unbiased. Otherwise, we have fully sighted, biased, opinion. Not science.