"Official" All amps sound the same thread - Page 7

Why?

How do you know a priori that there is a audible difference to hear?

If there is a fault with the test, is the problem the level matching or the bias controls?

This sheds new light on my ignorance.

I'll bite, exactly what does a power amp actually do???

I mean, I have 4 of them and I need to know.


I'll bite again.

How does one tell whether "they actually perform differently"???

Cheers

I do agree that if you feel there is a difference you should be able to prove it in a DBT. When I studied stats it was 80% correlation (IIRC) but that was about 23 years ago now.

Obviously there is more to life that proving everything to yourself by time consuming tests. Some things are obvious and tests are a formality. If you are ever in Denver then PM me and we can do your DBT.

BTW how do scientists disprove the existence of unicorns since all test must be blind?

It's under warranty, but as I said earlier I have five of these guys and have used them with three subs and I've heard the same differences. That's good enough for me, but I guess there is always the possibility of a bad batch or run from crown.

Doh.... I did mean warmer air holds more humidity! Brain fart!

Ha ha. I've taken allergy med for years and they've done nothing but empty my wallet.

And as I stated a DBT is only as good as the test. Lies lies and statistics as they say.

krabapple said: "Unicorns may exist too. But if you propose them as an explanation for something, it's your job to provide the evidence.".

They do exist. With 4 points. Accompanied by a 10-pointer. They have been taking bird food all Fall behind my house. Haven't bother to take a photo as they are too common.

Well, no, he actually gave more reasons than that. Why is it you guys are never able to comprehend the value of *qualifiers*?


Then I suspect he is only 'well respected' by other fans of audiophile Kool-Aid.
Care to name him?


Yeah, because audio magazine journalists are notorious for their adherence to scientific standards of proof.

I can run a three-minute mile. And since I, too, was a well-respected journalist at one time (before I found a non-dying field to work in), you have to accept the possibility that I really can.

He's might be following this thread.

The one I spoke of probably is.

Wonderful line. May I steal it?

Hmmmmmm.......

I seem to have missed that part.

And what about comparing SS to tube to "switching" amps (Class D)?

Any other limits on this?

All I read was that ALL amps sound the same, provided that they are reasonably close with respect to power output and can drive the load (speaker) properly, and the volume has been measured at several frequencies and matched to within 1/3 of a DB, and ????(I know I left a few others out).

I would imagine that if you got said amps to have the same measurements in as many ways as possible, they would tend to sound the same.

Sorta. They don't have to be "reasonably close" power-wise, as long as the less powerful one can drive the load adequately. And you really ought to be within 0.1 dB. And no, you haven't left any out.


Well, "as many ways as necessary" turns out to be only twopower and frequency response. But that's just the pointmost amps, in most typical home situationsare similar enough on these two parameters that there's no reason to predict that they would sound different. And they don't.

Which, of course does not mean that had we listened louder and gone through all the matching, etc., that we would now find that the less capable amp on paper was in fact less capable in practice.

I'm trying to look at this as open mindedly as possible, and doing a little reasearch into areas that I honestly have very little background in.

I went to Wikipedia and found that there are several types of measurable distortion in the area of analog reproduction (don't know if all of them apply equally to all forms of amplification).

Quote:

Measurable performance

[edit] Analog electrical
Frequency response
The signal should be passed at least over the audible range (usually quoted as 20 Hz to 20 kHz) with no significant peaks or dips. The human ear can discern differences in level of about 3 dB in some frequency ranges, so peaks and troughs must be less than this. Much modern equipment is capable of less than ±1 dB variation over the entire audible frequency range. Rapid variations over a small frequency range (ripple), or very steep rolloffs are considered undesirable as they can correspond to resonances associated with energy storage which produce delayed echoes and hence colouration, or decreased quality, of the sound.
Total harmonic distortion (THD)
In music material, there are distinct tones, and some kinds of distortion involve spurious double or triple the frequencies of those tones. Such harmonically related distortion is called harmonic distortion. For high fidelity, this is usually expected to be < 1% for electronic devices; mechanical elements such as loudspeakers usually have inescapable higher levels. Low distortion is relatively easy to achieve in electronics with use of negative feedback, but the use of high levels of feedback in this manner has been the topic of much controversy among audiophiles see electronic amplifier. Essentially all loudspeakers produce more distortion than electronics, and 1-5% distortion is not unheard of at moderately loud listening levels. Human ears are less sensitive to distortion in the bass frequencies, and levels are usually expected to be under 10% at loud playback. Distortion which creates only even-order harmonics for a sine wave input is sometimes considered less bothersome than odd-order distortion.
Output power
Output power for amplifiers is ideally measured and quoted as maximum Root Mean Square (RMS) power output per channel, at a specified distortion level at a particular load, which by convention and government regulation, is considered the most meaningful measure of power available on music signals, though real, non-clipping music has a high peak-to-average ratio, and usually averages well below the maximum possible. The commonly given measurement of PMPO (peak music power out) is largely meaningless and often used in marketing literature; in the late 1960s there was much controversy over this point and the US Government (FTA) required that RMS figures be quoted for all high fidelity equipment. Music power has been making a comeback in recent years. See also Audio power.
Power specifications require the load impedance to be specified, and in some cases two figures will be given (for instance, a power amplifier for loudspeakers will be typically measured at 4 and 8 ohms). Any amplifier will drive more current to a lower impedance load. For example, it will deliver more power into a 4-ohm load, as compared to 8-ohm, but it must not be assumed that it is capable of sustaining the extra current unless it is specified so. Power supply limitations may limit high current performance.
Intermodulation distortion (IMD)
Distortion which is not harmonically related to the signal being amplified is intermodulation distortion. It is a measure of the level of spurious signals resulting from unwanted combination of different frequency input signals. This effect results from non-linearities in the system. Sufficiently high levels of negative feedback can reduce this effect in an amplifier. Many believe it is better to design electronics in a way to minimize feedback levels, though this is difficult to achieve while meeting other high accuracy requirements. Intermodulation in loudspeaker drivers is, as with harmonic distortion, almost always larger than in most electronics. IMD increases with cone excursion. Reducing a driver's bandwidth directly reduces IMD. This is achieved by splitting the desired frequency range into separate bands and employing separate drivers for each band of frequencies, and feeding them through a crossover filter network. Steep slope crossover filters are most effective at IMD reduction, but may be too expensive to implement using high-current components and may introduce ringing distortion.[3]
Noise
The level of unwanted noise generated by the system itself, or by interference from external sources added to the signal. Hum usually refers to noise only at power line frequencies (as opposed to broadband white noise), which is introduced through induction of power line signals into the inputs of gain stages. Or from inadequately regulated power supplies.
Crosstalk
The introduction of noise (from another signal channel) caused by stray inductance or capacitance between components or lines. Crosstalk reduces, sometimes noticeably, separation between channels (eg, in a stereo system). It is given in dB relative to a nominal level of signal in the path receiving interference. Crosstalk is normally only a problem in equipment in which several audio channels are handled in the same chassis.
Common-mode rejection ratio (CMRR)
All electronic equipment with inputs is susceptible to this problem. In balanced audio systems, there are equal and opposite signals (difference-mode) in inputs, and any interference imposed on both leads will be subtracted, canceling out that interference (ie, the common-mode). CMRR is a measure of a system's ability to ignore any such interference and especially hum which arises at its input. It is generally only significant with long lines on an input, or when some kinds of ground loop problems exist. Unbalanced inputs do not have common mode resistance; induced noise on their inputs appears directly as noise or hum.
Dynamic range and Signal-to-noise ratio (SNR)
The difference between the maximum level a component can accommodate and the noise level it produces. Input noise is not counted in this measurement. It is measured in dB.
Dynamic range refers to the ratio of maximum to minimum loudness in a given signal source (eg, music or programme material), and this measurement also quantifies the maximum dynamic range an audio system can carry. This is the ratio (usually expressed in dB) between the noise floor of the device with no signal and the maximum signal (usually a sine wave) that can be output at a specified (low) distortion level.
Since the early 1990s it has been recommended by several authorities including the Audio Engineering Society that measurements of dynamic range be made with an audio signal present. This avoids questionable measurements based on the use of blank media, or muting circuits.
Signal-to-noise ratio (SNR), however, is the ratio between the noise floor and an arbitrary reference level or alignment level. In "professional" recording equipment, this reference level is usually +4 dBu (IEC 60268-17), though sometimes 0 dBu (UK and Europe - EBU standard Alignment level). 'Test level', 'measurement level' and 'line-up level' mean different things, often leading to confusion. In "consumer" equipment, no standard exists, though −10 dBV and −6 dBu are common.
Different media characteristically exhibit different amounts of noise and headroom. Though the values vary widely between units, a typical analogue cassette might give 60 dB, a CD almost 100 dB. Most modern quality amplifiers have >110 dB dynamic range, which approaches that of the human ear, usually taken as around 130 dB. See Programme levels.
Phase distortion, Group delay, and Phase delay
A perfect audio component will maintain the phase coherency of a signal over the full range of frequencies. Phase distortion can be extremely difficult to reduce or eliminate. The human ear is largely insensitive to phase distortion, though it is exquisitely sensitive to relative phase relationships within heard sounds. The complex nature of our sensitivity to phase errors, coupled with the lack of a convenient test that delivers an easily understood quality rating, is the reason that it is not a part of conventional audio specifications.[citation needed] Multi-driver loudspeaker systems may have complex phase distortions, caused or corrected by crossovers, driver placement, and the phase behaviour of the specific driver.
Transient response
A system may have low distortion for a steady-state signal, but not on sudden transients. In amplifiers, this problem can be traced to power supplies in some instances, to insufficient high frequency performance or to excessive negative feedback. Related measurements are slew rate and rise time. Distortion in transient response can be hard to measure. Many otherwise good power amplifier designs have been found to have inadequate slew rates, by modern standards. In loudspeakers, transient response performance is affected by the mass and resonances of drivers and enclosures and by group delay and phase delay introduced by poorly-designed crossover filtering or inadequate time alignment of all the loudspeaker's drivers. Most loudspeakers generate significant amounts of transient distortion, though some designs are less prone to this (e.g. electrostatic loudspeakers, plasma arc tweeters, ribbon tweeters and horn enclosures with multiple entry points).
Damping factor
A higher number is generally believed to be better. This is a measure of how well a power amplifier controls the undesired motion of a loudspeaker driver. An amplifier must be able to suppress resonances caused by mechanical motion (e.g., inertia) of a speaker cone, especially a low frequency driver with greater mass. For conventional loudspeaker drivers, this essentially involves ensuring that the output impedance of the amplifier is close to zero and that the speaker wires are sufficiently short and have sufficiently large diameter. Damping factor is the ratio of the output impedance of an amplifier and connecting cables to the DC resistance of a voice coil, which means that long, skinny speaker wires will undo the benefits of good electronic damping performance from the amplifier. A damping factor of 20 or greater is considered adequate for live sound reinforcement systems, as the SPL of inertia-related driver movement is 26 dB less than signal level and won't be heard.[4] Negative feedback in an amplifier design generally increases its damping factor.[

End quote.


Sorry for the long quote.


Seems to me that there are several variables here which could lead to perceived differences.

I was primarily interested in when these forms of measurable distortion were discovered. I was going to ask if prior to our knowledge of them, these were present - of course they were, we just either did not know about them, or did not have a way/sophisticated enough equipment to measure them.

Do you think we know about all forms of distortion which can be introduced by amplifiers, or does the possibility exist that we are still learning?

Would that possibly lead to the different opinions on this?

Sure, they could, but extensive listening tests (see, once again, Nousaine's review, cited above) have demonstrated repeatedly that they don't, assuming the amp is functioning properly.


In a sense, all distortion is the sameit's just a difference between the input signal and the output signal. And we can measure it all, simply by comparing the two. The types of distortion you list are just characterizations of aspects of that overall distortion. We could characterize distortion in different ways, but the bottom line is still the sameassuming enough power and flat frequency response, amps don't sound different. "Discovering" new types of distortion isn't going to change that.

It's a question of cause and effect. If we had a bunch of positive controlled listening tests between amps whose measurements tell us they should sound identical, then we'd need to wonder what it is we're missing in our measurements. But we don't have such results, so we don't have anything to explain. What you're asking is whether there are possible causes for an effect that doesn't exist.

As for "learning," people seem to forget that amps are not mysteries of the cosmos. They are man-made objects. Of course we know how they work (Bob Lee does, anyway!), and they are not going to serve up new mysteries in the future.


What leads to different opinions on this is willful ignorance.

This is redundant. All objectivists believe amps can sound different.

What separates objectivists from subjectivists is that objectivists believe there are identifiable physical causes when amps sound different. Subjectivists believe in magic.

I am sharing my experience in 10 min of free time. Truth is there is no time to share support as I simply don't have time to "support". Have been around for long time, in some forums still have some stars. I suggest your get a bit more relaxed in your approach. You seem to be a bit over the edge, so don't be offended if I simply don't feel compelled to respond to your...well, whatever they are.

You mean when two amps sound different, they'll measure different in some way? I thought when they sound different, it means they'll measure the same.

So-called "subjectivists" believe the measurable differences that exist can be audible. But please continue to willfully distort any viewpoint other than your own. It's very revealing.

How do we measure tone color or timbre?

DOH! (Whack self on forehead)

Somehow, I missed the link!

I'll try to read and understand as much of that article as I can. Much of what he says makes sense on the surface, but the devil is in the details as they say. And I believe that many of those details are beyond my true comprehension.

Of course there are. There are virtually an infinite number of variable combinations that could come into play. What we have here are a select few who think that because several documented double blind tests have shown negative results, that all similar claims of audible differences have to be bogus.

This is not genuinely scientific or intelligent behavior. It's also not how truly knowledgeable people conduct themselves. You're dealing with a bunch of wanna be scientific, self-delusional hacks. They've read some things and now think they know everything, so they go around putting other people down for their own self-aggrandizement. This allows them to continually convince themselves they have some special insights that only a select, elite few are privy to. I'm not a psychologist, but I would guess it fills some kind of self-inferiority complex.

So, I wouldn't waste your time, but I suspect you'll figure that out soon enough (if you haven't already).

Frequency response should pretty much cover it.

No. You may have met people who believe amps don't sound different, but they are just as ignorant as people who think amps generally sound different.

Objectivists believe amps sound different under conditions that make them sound different.

[quote=RWetmore;15739236] They've read some things and now think they know everything, so they go around putting other people down for their own self-aggrandizement. This way they can convince themselves they have some special insights that the common masses are not privy to. I'm not a psychologist, but I would guess it fills some kind of self-inferiority complex.
QUOTE]


well that is part of my training and yes, that is generally how it works unless it is driven my a psychotic process. lots of angry narcisissm here. with a delightfylly obsesive-compulsive and rigid flair.


to be fair many subjectvivts believe that some ptentially measurable differences do likely exit that explain sound differences. and speaking pf the pharma industry they do studies to prove lies all the time, sometimes using DBT as a surreptitious but convincing cloak. often times as well studies designed to study the very same thing usigh the same methodology have very diffent results--are they explainable--certainly some physical thing makes this happen and is probably measurable but we often don't know what it is.

If you think the only evidence we have is a few blind tests, then you are being willfully ignorant.


Rest assured, when I compare myself to you, inferiority is not the problem.

We wannabe scientific hacks present real scientific evidence to back up what we say. What you present is well represented by the paragraph above.

As for what the common masses are privy to, I'm not a scientist at all, and yet I've managed to figure this stuff out. The people who haven't figured it out would rather not. Believing in magic is much more fun.

And this differs from believing in magic how, exactly? Not only are you claiming that never-measured differences exist, but you're also claiming that sound differences exist, without any evidence at all. You're claiming that there's some theoretical cause for an effect you can't even show is real.