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Can amplifier speed and resolution be measured?

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#1
Lately, the JDS Labs Atom has been making headlines due to its wonderful measurements (and yes I still have yet to receive mine... it's being brought to me by usps...).

Yet, many of those who "reviewed it" through subjective impressions did appreciate the performance "for the price", but have been quick to dismiss it as having quite a "lack of speed and resolution" compared to their other much fancier products (perhaps in an attempt to prevent buyers remorse from their audience or in statement of true facts).

Which sparks some curiosities in me:
1- Can amplifier speed and resolution be measured?
2- If so, by what metric?
3- Would this metric be quite audibly noticeable within lenient and strict threshold?

Thank you!
 
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sergeauckland

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#2
Speed and resolution, like pace and timing or musicality are meaningless words used by sloppy subjective reviewers.

Speed, as in Slew rate, can be easily measured and ANY amplifier of hifi pretentions can comfortably perform adequately. Resolution similarly, if meaning signal to noise ratio, is more than adequate in every amplifier, but neither slew rate nor S/N ratio are what reviewers mean, it's an airy-fairy armwaving concept only they understand, and therefore of no validity whatsoever.

S
 

SIY

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#3
What Serge said. Important parameters are flat frequency response (<0.1dB, 20 Hz- 20 kHz), low output impedance (<5% of the load nominal impedance), low distortion (<0.01% or so), high enough power to drive the load to 120dB SPL peaks, and low noise (depends on the sensitivity of the load).

Just about any engineered amp made in the past 30 years or so will be audibly transparent. When reviewers talk about speed and resolution, they may as well be rating refulgence and obsequiousness. Amplification is a long-solved problem.
 

FrantzM

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#4
Lately, the Atom has been making headlines due to its wonderful measurements (and yes I still have yet to receive mine... it's being brought to me by usps...).

Yet, many of those who "reviewed it" through subjective impressions did appreciate the performance "for the price", but have been quick to dismiss it as having quite a "lack of speed and resolution" compared to their other much fancier products (perhaps in an attempt to prevent buyers remorse from their audience or in statement of true facts).

Which sparks some curiosities in me:
1- Can amplifier speed and resolution be measured?
2- If so, by what metric?
3- Would this metric be quite audibly noticeable within lenient and strict threshold?

Thank you!
All reviews conducted with full knowledge... That says it all.

a snip from the review , I wrote for a magazine ...
The more expensive Amps will , of course, have more resolution and the ever important PRaT. The THX is good for the price but if you want the next to ultimate in Headphone amplifier, The Zywhgry Silver Iridium Mark VIII @ $8900 is almost unbeatable, unless you want to spend more just get outright the vibranium-plated Zeguyt "El Matador", a direct heated Cathode SET amplifier @ $25,000.. There's none better ...

:p
 
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#5

andreasmaaan

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#6
“Speed and resolution” - I guess “pace, rhythm and timing” got to be too much of a joke.
 
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#7
What do people mean when they speak about something that performs the act of "resolving detail"?
 

March Audio

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#8
What do people mean when they speak about something that performs the act of "resolving detail"?
not a lot in objective terms. Perhaps an (erroneous) emphasis on high frequencies, or due to certain types of distortion maybe. Not many amps will fail to resolve the detail that you can actually hear.
 
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Lbstyling

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#10
When you hear speed and/or resolution you are usually listening to added 2nd and 3rd harmonics. 'high end' amps (naim cpr instance) add it combined with other techniques for a 'house sound'.

Before you spit your Cheerios out with expletives, remember that 2nd harmonics are natural in real live sound.

Watch this and see what I mean...

Crazy as it sounds, I actually add 2nd harmonics on a delay to the signal for my music through my PC/DIY system When demoing it. (Shush! Dont tell anyone!!);)

Now, if you were a manufacturer who wants to target selling amps to rock music enthusiasts, you just add 3rd harmonics in your design via poorly performing tube topology etc. (Added bonus- clipping performance is smooth when compared to SS amps, meaning the track compresses when you turn the dial up to 11!

Alternatively, you massively overrate the amp compared to what you write on the box....
Watch this ancient 100w NAD amp deliver 1800w in test...


Almost any competition would be clipping WAY before this amp was even starting to warm up. When amps clip, they sound harsh, hard and low resolution.
 

stereo coffee

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#11
If we see in schematic form what a good amplifier consists of, your three questions might begin to resolve
1- Can amplifier speed and resolution be measured?
2- If so, by what metric?
3- Would this metric be quite audibly noticeable within lenient and strict threshold?

As example a cascode circuit has many inherent advantages over a single stage, if we weed out amplifiers
lacking a properly implemented cascode we are left with just a handful of amplifiers to consider.

Another example is the feedforward techniques and bridge balancing known as Quad's current dumping

So the metric as I see it is to see amplifiers with outstanding uses of circuitry - what usually follows is
outstanding audio, to answer your third question.
 

SIY

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#12
If we see in schematic form what a good amplifier consists of, your three questions might begin to resolve
1- Can amplifier speed and resolution be measured?
2- If so, by what metric?
3- Would this metric be quite audibly noticeable within lenient and strict threshold?

As example a cascode circuit has many inherent advantages over a single stage, if we weed out amplifiers
lacking a properly implemented cascode we are left with just a handful of amplifiers to consider.

Another example is the feedforward techniques and bridge balancing known as Quad's current dumping

So the metric as I see it is to see amplifiers with outstanding uses of circuitry - what usually follows is
outstanding audio, to answer your third question.
Can you point out any evidence that any two engineered* amps, regardless of topology, can be distinguished by ear alone if neither is clipping and levels are matched?

*engineered = designed for low distortion, low output impedance, flat frequency response
 

stereo coffee

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#13
Can you point out any evidence that any two engineered* amps, regardless of topology, can be distinguished by ear alone if neither is clipping and levels are matched?

*engineered = designed for low distortion, low output impedance, flat frequency response
To answer your question, and I shall seek to find your exact requirement, but for the moment I refer to the
attached article on page 4 http://www.meridian-audio.info/public/interview[4446].pdf
Peter Walker founder of Quad was often quoted as saying "All amplifiers sound the same "

In the article Peter corrects himself by referring to the difference made by extending the bandwidth of amplifiers
( incidentally one of the large advantages of cascodes ) by saying " Why all amplifiers sound different, because it gave at least
twelve reasons why amplifiers sound different that people never, or very rarely check up on when they do comparisons.
You've got to have the same bandwidth of amplifier, because the bandwidth affects what the speaker does, not always to
its advantage"

Another audio designer David Blackmer founder of DBX refers also to the problems of limiting bandwidth in his article
http://wilson-benesch.com/reviews/Life_Beyond_20kHz_Blackmer_SVC_Sep-1998.pdf
and gives insight into seeking perceptual perfection
 

stereo coffee

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#14
Another valid point is the singular assumption that amplification does or does not contains perception of difference
when equally it also must be applied to attenuation
 
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#15
What do people mean when they speak about something that performs the act of "resolving detail"?
Nobody knows. As said earlier, audio amplification is a solved problem. There is a lot of improvement to be made in loudspeaker diaphragms but not amplification. The technology has also become extremely cheap. A good analogy is a wristwatch. In the 80s', the Japanese decimated the Swiss watch industry by mass-producing quartz movements. Many Swiss watchmakers shutdown completely. The rest survived by moving up the value chain by adding unnecessary complications to watches. Now, those watches are a luxury item. The same thing is happening with the audio industry. Boutique shops overdo the engineering and market it as an advantage when the vast majority of people can't hear the differences.
 
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#16
... a "lack of speed and resolution" compared to their other much fancier products (perhaps in an attempt to prevent buyers remorse from their audience or in statement of true facts).
Maybe it is an attempt to prevent their own buyer’s remorse even more than that of their audience. :) There are a lot of measurable amplifier specifications (slew rate, bandwidth, offset voltage, common mode rejection ratio, gain, output impedance, input impedance, IIP2/IIP3 or other linearity metrics, noise figure, ... even “latency” in the case of a distributed amplifier) but “speed” is not one of them.
 

amirm

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#17
Another audio designer David Blackmer founder of DBX refers also to the problems of limiting bandwidth in his article
http://wilson-benesch.com/reviews/Life_Beyond_20kHz_Blackmer_SVC_Sep-1998.pdf
and gives insight into seeking perceptual perfection
That interview is 20 years old. Since then, there has not been support for what David is stating regarding impact of high bandwidth on bass performance. I have done a lot of comparisons of high-res against CD in controlled blind tests and I don't recall at all the bass changing. So what he says is theoretically impossible, likely is. :)
 

stereo coffee

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#18
That interview is 20 years old. Since then, there has not been support for what David is stating regarding impact of high bandwidth on bass performance. I have done a lot of comparisons of high-res against CD in controlled blind tests and I don't recall at all the bass changing. So what he says is theoretically impossible, likely is. :)
What was the hi res equipment source / attenuator / power amp you were comparing with ? Did it have known spec above 20khz
to properly compare with CD ? As David goes on to say "something is there" I think his approach of discovery is the better one to take
 
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#19
What was the hi res equipment source / attenuator / power amp you were comparing with ? Did it have known spec above 20khz
to properly compare with CD ? As David goes on to say "something is there" I think his approach of discovery is the better one to take
Just to make sure I understand your argument correctly: You want Amir to justify his statements with measurements and data (your request for equipment, and specs associated with his statement) but “something is there” from David is sufficient for you to conclude that his (David’s) approach to discovery is a better?
 
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stereo coffee

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#20
Discovery is always the better approach... Amir's comment looked to me rushed and a generalisation, to not exactly say what equipment as hi-res was actually being used against CD to be able to say if extended bandwidth might cause bass to change.
 
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