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General debate thread about audio measurements

RayDunzl

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To reach 67dB how many watts is that?
Guessing less than one dissipated at the speakers (each).

Using the MartinLogans (so I can measure speaker voltage), and seeing 0.7Vpk with a multimeter (with max hold), at 4 Ohms, that's 0.13 watts peak. (or some similar small amount).

From your own system's volume knob (pot), which position on a clock would that be?
On the preamp, it spins freely and is unmarked, but the display reads from 0 to 151.

At the moment, the preamp display is "30" (a unitless number, but something like .25 to .5dB per digit, never measured critically).

Is your volume control analog or digital?
Have both. Preamp has some kind of electronically selectable resistor set (analog), DAC and DSP recalculate the digits.
 
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NorthSky

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Cool, educational. That's why they say that the first watt is important. You want that watt, and below...0.1 watt, and just above, 3 watts or 5, clean.

I was just wondering if we can get a cleaner volume control in the analog or digital domain.

Ray, do you also listen with headphones sometimes?
 

trl

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Alright, how loud are we listening to, where on that dial are we turning up that volume control knob (potentiometer, volume attenuator)? How much break pedal (attenuation) are we releasing? What resistance is applied say when we are using normal power...less than 3 watts RMS? @ what average level are we listening to our music? What is the meter showing...0.3 watts? ...Little bit more...1.0 watts? It depends, passive or active listening...background music or front end serious music.
...From a normal stereo preamp, from a headphone amp.


@ low volume level listening we usually measure larger amount of THD.
And the more we crank the volume up the distortion level decreases, up to the power amp limit, where the distortion rises abruptly and clips.
With a quality amp the level of THD is low from 0.001 watts to say 5 watts.
Some amps have larger level of THD @ very low power...say less than 3 watts.

Using a quality amp, how much influence a volume pot can have on the sound output...measurable distortion level? Are there better potentiometers with less measured distortion, and if yes, what are the best ones and why are they measuring better?
The really potential issue might be with a DAC having built-in digital control is the noise level under really quiet environments and very sensitive speakers/headphones. The reason for this is the lack of gain attenuation between the input stage and output stage, basically the entire noise of the DAC's output + I/V stage + LPF stage + preamp stage + output stage is on your headphones/speakers. This noise only manifests with very sensitive IEM's for example or with very sensitive speakers (depending what you're going to amplify and drive). A regular potentiometer places between LPF stage and the preamp stage will lower both noise & volume and background noise will be virtually non-existent or outputs.

I've seen this behavior on Burson PLAY (ES9018K2M with built-in volume contro, 4V RMS/channel on DAC's outputs), but only with very sensitive 16 Ohms IEM's: placing a resistive divider or a regular 10 KOhms pot. "in the middle" reduced the background noise and the output volume, of course. Basically, "pot. in the middle" behavior is also why Objective2 has virtually nonexistent noise on outputs when driving sensitive IEM's.
 

esotechik

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What about statistical (ACF) delta-sigma conversion errors?
Many R2R DACs has "no missing codes" in description.
Audio Precision with D-S ADC and long averaging cannot detect ACF errors.
AP is old instrument initial for analog circuits, with some digital features.
sdm_fail.png
https://en.wikipedia.org/wiki/Analog_signal_processing#Linear_time-invariant_(LTI)

"Linearity and time-invariance are important because they are the only types of systems that can be easily solved using conventional analog signal processing methods. Once a system becomes non-linear or non-time-invariant, it becomes a non-linear differential equations problem, and there are very few of those that can actually be solved. (Haykin & Van Veen 2003)"

Delta-sigma DACs is not LTI system, has all missing codes and significant noise shaping.

ACF_random.png
 

amirm

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AP is old instrument initial for analog circuits, with some digital features.
Everything we want to analyze is analog. Don't care what happens upstream. We want to know what the analog signal is doing. The AP digitizes this analog signal and then processes it in software.

On the rest of your post, I am not clear what the issue is. DACs that we deal with are multibit so limit cycles are much less of a problem with them. Your references seem old and deal with 1-bit quantizers????
 

esotechik

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DACs that we deal with are multibit so limit cycles are much less of a problem with them
"Much less" is only words, not measurements.
IMHO we need true SAR ADC (no missing codes, without noise shaping) + Eye Diagram with meander signals, this is instrumental method vs. AK5394+FFT in AP.
https://www.diyaudio.com/forums/equ...rformance-audio-adc-project-ltc2380-24-a.html

My first (green) picture relating to fifth order sigma-delta modulator.

https://m.eet.com/media/1166738/295165-tmw_eye_freescale_fig4.jpg
 

amirm

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"Much less" is only words, not measurements.
IMHO we need true SAR ADC (no missing codes, without noise shaping) + Eye Diagram with meander signals, this is instrumental method vs. AK5394+FFT in AP.
https://www.diyaudio.com/forums/equ...rformance-audio-adc-project-ltc2380-24-a.html

My first (green) picture relating to fifth order sigma-delta modulator.
Like you said, that is only words, not measurements. You are not showing what the Audio Precision analyzer can do. So let's set the conditions similar to yours and compare:
APX Loopback with 1 million point FFT.png


Your graph on the left is using relative dB but unfortunately 0 dB is not set to signal level (what good is relative dB then???). Mine is set to 0 dB so compensating for that, the APx is much, much better. There is only one harmonic component at whopping -157 dB down from signal. In your case, you are getting -130 dB (again, referenced to 0 dB, not -6dB). You also have fair bit of noise and distortion components beyond that harmonic.

How does the APx55 get such superlative performance? It does so by using two ADCs. One handles the signal and then the other notches it out and measure what is left. The second ADC therefore is operating with no distortion since the signal is all gone. Through signal processing, the output of the two ADCs are then summed together. This is how you build a high-performance audio analyzer. Not just by brute force but rather, engineering smarts.

Noise floor is also lower in APx555 analyzer:
APX Loopback noise floor with 1 million point FFT.png


The above with the signal generator on but set to zero which disadvantages the APx555. Still, it beats your solution by 15 dB.

All of this is beside the point: the analyzer only needs to be better than devices we are testing. And the APx555 does that well, able to differentiate between the highest performance audio components we have tested with it.
 

esotechik

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Noise floor is also lower in APx555 analyzer:
1 000 000 point averaging is a bad idea for detect occasional "glitches".
Digital oscilloscopes has flash or SAR ADC, not delta-sigma.
Old phonograms (<1995 yr.), digitized via SAR ADC is more preferred vs. modern, generated by D-S ADC (with equal music styles and dynamic range).

This is other test system:
MSB_DAC-Measurement-Flow-Chart-Pico.jpg
 
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Shadrach

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Well, I've waded through this one.:confused:
I've really only got one point to make but it's really important; there is no music!
People keep talking about the effects of various parameters on the music. These boxes of electronics don't make music, they don't transport music, they don't decode music, they wouldn't know music if you took them to a concert. There is no music on the medium, no music comes out of the speakers. The music is all in your head.
It's signal processing. The measurements are about how well, or badly a particular unit does this. The comparisons are to other signal processing units. Some measure better than others. You may well not be able to tell the difference by ear. That's not the point.
 

amirm

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1 000 000 point averaging is a bad idea for detect occasional "glitches".
There is no million point averaging. The averaging and FFT lengths are set exactly to what was measured in the link you provided. For one test it is 20 averages and the other 10. And if that gets rid of occasional "glitches," that much the better. It makes the measurement system immune to issues you imagine to be there (but not demonstrated with any measurements).
 

Shadrach

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Interesting thread.;)
A point about measurement. It doesn't matter which yardstick one uses as long as you use the same yardstick for every unit measured. It's a very basic rule when measuring anything. If the divisions on your stick are very small then your accuracy is better. The point that to some amirm's tolerances are too tight, would have some merit if none of the units fell within tolerance. That hasn't been the case here from what I've read. If company A can make a product that falls within these tolerances for X amount of money, then it seems fair to point out that company B's product at Y amount of money doesn't.
To the best of my knowledge amirm only applies a value judgement to the product briefly at the end of his reviews. This is his subjective evaluation. You can dismiss, it or not bother reading it as I do.
The measurements are about design competence; they are not about whether or not it's going to sound good to you.
Part of amirm's mission (I'm sure he will correct me if I'm wrong) is to demonstrate that often the subjective evaluations of equipment are not born out by the measurements. So, if we talk about a building brick for a moment, the measurements will tell you its size, how much compressive force it can take before deformation, its colour etc. In your building project you may not need a brick that can take 40 tons per square inch and a 5 micron dimensional tolerance and is yellow; a red brick with 1mm tolerance at 20 tons limit may well do the job. Buy the red brick then but it's pointless trying to argue that one brick is better than the other.
 

sergeauckland

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Interesting thread.;)
A point about measurement. It doesn't matter which yardstick one uses as long as you use the same yardstick for every unit measured. It's a very basic rule when measuring anything. If the divisions on your stick are very small then your accuracy is better. The point that to some amirm's tolerances are too tight, would have some merit if none of the units fell within tolerance. That hasn't been the case here from what I've read. If company A can make a product that falls within these tolerances for X amount of money, then it seems fair to point out that company B's product at Y amount of money doesn't.
To the best of my knowledge amirm only applies a value judgement to the product briefly at the end of his reviews. This is his subjective evaluation. You can dismiss, it or not bother reading it as I do.
The measurements are about design competence; they are not about whether or not it's going to sound good to you.
Part of amirm's mission (I'm sure he will correct me if I'm wrong) is to demonstrate that often the subjective evaluations of equipment are not born out by the measurements. So, if we talk about a building brick for a moment, the measurements will tell you its size, how much compressive force it can take before deformation, its colour etc. In your building project you may not need a brick that can take 40 tons per square inch and a 5 micron dimensional tolerance and is yellow; a red brick with 1mm tolerance at 20 tons limit may well do the job. Buy the red brick then but it's pointless trying to argue that one brick is better than the other.
For many years now, I've applied the principle of 'adequacy' to any judgements I make about anything. What do I need the item to do, and how well, then look at the specs / measurements to decide which item comes closest. I then buy the cheapest that meets my requirements. The important part is to specify one's requirements completely, including such intangibles as 'build quality', serviceability' and 'appearance' which I accept are subjective, but it's my spec I'm buying against. What this means is that I don't necessarily by the cheapest of any one item, as even if the measurements are adequate, the item fails on the build quality or other 'subjective' parts.

It can therefore be said that I'm no different to subjectivists who buy on perceived (non blind tested or level matched) sound quality, but in reality, because evaluations are not done blind, their choice is perhaps made on anything but sound quality, whereas in my case, I never bother to listen first to anything I buy in audio. I just need a detailed set of measurements, which is why I find this forum so useful. It's a pity that it's impractical for Amirm to do loudspeaker measurements....what's wrong with an anechoic chamber at home......

I've also been criticised for buying what's 'adequate' rather than what's excellent, but what gets missed is that what I consider adequate may be their excellent, or indeed vice versa.

As very little in the way of HiFi electronics isn't transparent these days, I don't see the problem with buying on facilities required and perceived build quality.

S
 

JJB70

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Indeed, in some ways the debate is often wrongly framed. If you like something because it looks nice, it is made of nice materials, you lust after a status symbol or you just think it sounds nice regardless of what anyone else thinks then nobody has to justify their choices to anyone else. It'd be a boring world if we all thought the same and acted entirely rationally all the time (how many of us chose our partners for rational and logical reasons?).
However, what is wrong is to deny the value of measurement in objective terms. If you buy something which is less accurate than alternatives or which costs 10x more than an alternative that measures the same then that's a personal decision but don't try and argue that measurements are wrong or that the magical and wondrous properties of audio signals cannot be measured. There is nothing especially unique or challenging about audio measurement if you have the necessary equipment and know how to use it. There is truth in the adage that if you can't measure it you can't improve it. All good engineering I have observed was based on sound application of good scientific and engineering principles and analytical tools are there to be used. Yes, you can like something or think it is nicer, but that isn't the same as trying to claim it is better in objective terms.
The danger I do see in measurement is that it is easy to become fixated on figures. Once you achieve audible transparency then while continued improvement is not a bad thing neither will it do much for the listening experience.
 

FrantzM

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Indeed, in some ways the debate is often wrongly framed. If you like something because it looks nice, it is made of nice materials, you lust after a status symbol or you just think it sounds nice regardless of what anyone else thinks then nobody has to justify their choices to anyone else. It'd be a boring world if we all thought the same and acted entirely rationally all the time (how many of us chose our partners for rational and logical reasons?).
However, what is wrong is to deny the value of measurement in objective terms. If you buy something which is less accurate than alternatives or which costs 10x more than an alternative that measures the same then that's a personal decision but don't try and argue that measurements are wrong or that the magical and wondrous properties of audio signals cannot be measured. There is nothing especially unique or challenging about audio measurement if you have the necessary equipment and know how to use it. There is truth in the adage that if you can't measure it you can't improve it. All good engineering I have observed was based on sound application of good scientific and engineering principles and analytical tools are there to be used. Yes, you can like something or think it is nicer, but that isn't the same as trying to claim it is better in objective terms.
The danger I do see in measurement is that it is easy to become fixated on figures. Once you achieve audible transparency then while continued improvement is not a bad thing neither will it do much for the listening experience.
Is there an emoji for liking a post a lot!!!?
Great Post.
 

Shadrach

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For many years now, I've applied the principle of 'adequacy' to any judgements I make about anything. What do I need the item to do, and how well, then look at the specs / measurements to decide which item comes closest. I then buy the cheapest that meets my requirements. The important part is to specify one's requirements completely, including such intangibles as 'build quality', serviceability' and 'appearance' which I accept are subjective, but it's my spec I'm buying against. What this means is that I don't necessarily by the cheapest of any one item, as even if the measurements are adequate, the item fails on the build quality or other 'subjective' parts.

It can therefore be said that I'm no different to subjectivists who buy on perceived (non blind tested or level matched) sound quality, but in reality, because evaluations are not done blind, their choice is perhaps made on anything but sound quality, whereas in my case, I never bother to listen first to anything I buy in audio. I just need a detailed set of measurements, which is why I find this forum so useful. It's a pity that it's impractical for Amirm to do loudspeaker measurements....what's wrong with an anechoic chamber at home......

I've also been criticised for buying what's 'adequate' rather than what's excellent, but what gets missed is that what I consider adequate may be their excellent, or indeed vice versa.

As very little in the way of HiFi electronics isn't transparent these days, I don't see the problem with buying on facilities required and perceived build quality.

S
I wish I was as utilitarian, but I'm not.
Joining this forum (always easier to blame someone else) encouraged me to buy the first bit of new kit I've bought for maybe 15 years.;)
I bought the JDS Labs Atom, purely on the specifications kindly supplied by amirm. I was curios to see if a state of the art product (I know it's cheap and plastic but it's measured performance is excellent and comparable to any hi end headphone amp I've read specifications on) sounded any different to my current tube driven effects box. I was able to make an informed choice thanks to amirm's measurements.
Out of curiosity I scoured the internet for reviews. Interesting to read there were a number of reviewers who while stating that it was a good value product, still implied that a high end (higher priced) product could be an upgrade.:facepalm:. Through impatience I cancelled the order and bought the Topping DX3 Pro which was instantly available. The Atom had already been dispatched when I cancelled so now I have both.
I've been listening to all three units a lot. I can perceive an audible difference between the WAD 83 and the other two very easily and I'm a bit disturbed that I have been content to listen to what to considerable distortion for many years now. So much for any audiophile credentials.:p
For the first time for many years I can sit and listen and think to myself 'so this is more like what that recording is supposed to sound like'.:cool:
I wouldn't have been able to do this without amirm's work here on ASR. I'll ignore the fact that he is just costing me money and undermining my complacency.:rolleyes:
I bought my Exposure amplifiers because I heard them in a friends system, like how they looked and had the money to spare. I've had them, with other stuff in between for over 20 years (I'm not hitting the consumer bracket very well either)
My loudspeakers are totally unsuitable for my current location, but I built them (a number of iterations now) and have got used to the sound they make.
I've tried other speakers, but I just don't have the same level of attachment and therefor, they don't sound as good, even if they are more accurate.
My complaint about ASR is amirm will insist on trying to have a life rather than measuring stuff all day.;)
 

JJB70

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I bought the JDS Atom, partly on the basis of how it measured, partly on the basis of my confidence in JDS as a company, a lot on the basis of it having achieved such great performance for peanuts. And I haven't been disappointed, for sure I would prefer a nicer metal case and would pay more for them to use something like the March Audio style casework but in terms of a headphone amplifier doing what a headphone amplifier needs to do then I honestly see no point going any further. I think it is a terrific product and a prime example of why excellent engineering and performance do not need to be expensive.
 

Krunok

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The danger I do see in measurement is that it is easy to become fixated on figures. Once you achieve audible transparency then while continued improvement is not a bad thing neither will it do much for the listening experience.
Very much so. And if you don't realise that simple truth you easilly end up spending your money at a component with better numbers which you won't be able to hear instead of another component of your listening chain where you would immediately notice improvement. Spending money on a DAC/amp with better numbers instead of buying better headphones/speakers is a typical example.
 
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