measurement bollocks.

> Well, because if they'd don't they are as useful as a chocolate teapot.

Useful to who?

I think you may have wholly missed my point. The audiophile press does not publish "proper" useful measurements because it is not in their interests to do so. It does not publish "proper" articles about how sound, sound perception and audio equipment works because it is not in their interests to do so. Audiophiles themselves are not really interested in either subject or else they would start to lose the beliefs that make them audiophiles.

> The audio press used to be more thorough, more rigorous.

This was before the audiophile phenomenon when the interests of both the home audio press and the home audio enthusiasts was very different to what it is today.

> The alternative is for others to fill the void - forums & blogs, which is fine

These are few and far between. A significant hobby interest in home audio rarely seems to survive a knowledge of what is important in sound reproduction in the home.

> but they seldom have access to the required test gear.

Reasonable computer based test gear costs peanuts compared to audiophile equipment. If they haven't got it then I would suggest it is because they are not really interested in it.

 

The answer of a true audiophile.

 

An AP is hardly peanuts. sure you can take basic measurements with a PC scope but the whole point of this thread is that those gross measurements don't tell the whole story, or even any useful part of it.

 

Some certainly do.

You can hear high levels of THD. Go back and read the research on amplifier distortion using listening panels done by Leak. Decades ago so nothing new.

You can also hear even quite subtle response errors.

You can hear IMD.

You can hear the effects of output impedance.

Those are fairly basic but many people ignore them, and make i'll informed choices by doing so.

We can start with the basics, which tell you lots, and work up from there.

 

I haven't missed the point at all.
I'm simply saying that in order to be of any use to a buyer, they need to up their game and include detailed technical testing.

I fully appreciate that they might be selling more copies by publishing purely subjective drivel, and that certainly serves their purpose but it doesn't help the buyer in any way.

Now you can argue that most people wouldn't understand such detailed and comprehensive testing, and you might have a point. Subjective testing has a lot to answer for in dumbing down the whole process over the years but doesn't mean we should just except it.

 

Personally, I'd love to read a review that accurately described what a piece of gear actually sounded like. I've yet to read even one in the past forty years that got close muchless nailed it. Frankly, I don't have any faith in the process at all.

As I see it, the magazines are good for product news and interviews with engineers in the field, otherwise, a complete waste of time.

 

I suspect it's partly due to how subjective the taste for sound is. One persons lean sound is another person's fat and rounded. The only way you could do it would be to compare certain sound qualities against other devices, which then requires the reader to have listened to a hell of a lot of kit.

 

Cherub, I expect you aren't far off the boil there, a reviewers taste for a certain sound may have as much effect on skewing the description of the sound of a piece of kit as the users preferences.

I think that's one of the benefits of having long timers like Martin Colloms review gear and Mikey Fremer, guys who have been at it for years. You build up a picture of the sound they like and also know when they are just blowing smoke up an advertisers arse.

 

Simon,

More than a hint of truth in the last statement, I would also go so far to venture than avery good portion of reviewers do not have the space or the qualifing equipment to actually review a piece of kit 'outside' their audio comfort zone or wish to either.

I would also venture to far as to suggest a great many of the current reviewers should have a career change, it is embarassing when you actually install equipment at some places of residence, not with standing their 'tunnel vision' approach to musical content or inability to actually understand the particular piece their are reviewing what ever that may be. YMMV


Currently I feel there are six or seven reviewers of merit (IE they have close to an impartial feel for the equipment, the room and supporting equipment plus the TIME and patience to listen and absorb the review piece in it's own context)
The rest leave a lot to be desired. YMMV

Back to the figures, Felix made some most valid points with regard to 'getting beneath' the stated measurements.

Also 'skewing' the way particular equipment is measured, the example of class 'd' and analogue switching amps is most apt, you would whince if you saw the 'noise' which sits ontop of the output signal from a switcher

However they are some pretty decent switchers around yet they perform very well in the audio frequency spectrum.

I would agree with high channel seperation, larger bandwidth's upto at least the 5th-7th harmonics, coupled with a low THD.

You can genuinely hear an amplifier that has 0.1% distortion, could you physically differenicate between 0.003 and 0.0003%?

Again all this entertaining to debate Simon, are you suggesting a new standard of universal measurement?


Tony

 

The situation with switching amps is by no means cut and dried.

The noise sitting on the signal, or the effects of this folding back into the audio band can be measured and demonstrated, but the audibility is the key. In the same way that Leak did testing not only to identify distortion but to then assess the effect on listeners.

There is little research into this at present and more certainly needs to be done in order to quantify the subjective effects on the listener.

I can certainly think of one user runing high power switching amps into Impulse Taus horns of all things, and is delighted with the results.

Tony, do you carry such amps and if so what are your thoughts compared to more standard SS and valve designs?

 

Rob - I'd agree with that; I've heard one very good Class D amp, and a some I don't rate at all.

The basis for many reported audible differences is probably dynamic effects anyway. Long ago Paul Miller used to measure and report noise floor modulation for amplifiers, exactly the kind of effect which makes for audible differences and which a single figure of merit cannot convey. For example I also suspect this one measurement would be hugely telling for competing Class D amps...

 

Ears versus instruments.
Question: In the case of an experienced reviewer of say 40 plus years of age,if a sine wave tone of 10Kc/s or above was superimposed on his test media would he hear it?And if he couldn't(as I suspect would be the case) how could you rely on anything else he said he heard?
I know that I could see it on a scope but otherwise I know it would be undetectable by me.

 

I don't think perfect hearing is the most important factor in judging sound. Experience and how your mind had learned to interpret the sound it receives is the key. Hence some quite old and deaf mixing engineers can produce better sounding recordings than others with perfect hearing. Our mind is the most powerful part of our hearing system.

 

Certainly if music came with 20khz sine waves superimposed on top then the kids would be pissed off, but would we care. Would it fold back lower down the audio band and modulate the signal further? Who knows.

I would find it hard to take value from the opinion of a deaf reviewer, but seeing as many reviews are little more than discussions of the box and a spec sheet rewrite it actually might not be as bad as we might think.

Tony, I wish i knew enough about measurement to be able to propose suitable measurements for publication. I know we aren't well served by most of the press currently.

 

Agreed...the difference is having the ability to recognize what moves the listener vs what sounds spectacular or impressive.

 

I can't really agree with that since what moves some, might not move others. A reviewer can't know that. However, the ability to hear is not as strongly related to the quality of ones physical ears as you might think.

 

Rob,

I would agree with this whole heartily, it is the implementation of ANY such technology that is the key to its success of dismissal in the audio arena.

Again, main power supply rails, switching frequency for the amplification section, dedicated fully super regulated style supplies for the control module, fully isolated digital and analogue ground planes, at least 4 layer high quality circuit boards, specific RFI/EMI shielding, high quality ouput stage filtering, FET selection and again isolation all play a key role in the finished articles performance.


They are a few designs around that are capable of serious results, The early B & O and Hypex modules have too limited a band width to provide serious performance, they can be made to sound good without question, they just lack musical engagement and emotion for me, however they do have a following and are well regarded in dark and solder fume filled cupboards and garages!

They key words here are 'audible' and how this is perceived by the individual, I have had some pleasing results by moving the switching frequencies of the amplifier into the higher pass bands, a lot of the well know switchers tend to use a switching frequency around the 500Khz mark, for me this is too low and (again for me) does not extend higher enough to 'hide' enough of the switching noise.

We like to use between 1.2 Mhz and 1.65Mkhz for optimum results in our designs, again the FET noise is also a key issue in this particular area.
Having experimented with multiple low pass values, I like to keep it between 90-120Khz depending on FET performance (gate noise, speed rfi emissions and vibration) and switching frequencies, they are various other issues which are factored into the equations too!

Contrary to most switcher designs these days, I prefer torriodial power, ultra quiet and fast rectification coupled with a two stage smoothing and storage bank, consisting of multiple capacitor banks each of around 240K, quality bypassing etc. We also incorporate a large DC blocking circuit into the psu as well.



As with all equipment Rob personal taste is paramount for a possible amplifier purchase, one form of technology can sound 'wrong' or not desirable to a potential buyer.

We stock all the amplification styles you mention Rob, we have very high quality solid state, with no op amps used at all just fully discrete, both class a/b and fully class 'a' designs and valve solid state hybrids.

Valves amps from Puresound to airtight and Waveac, single ended to push pull, each of these designs brings their own flavour to the party, though unless you are running 845's or 211's you are fairly limited to speaker choice, needing at least a 92dB sensitive unit to fully bring out the most of the amplifier.

This may surprise you guys I have admiration for a good 2A3 design and a quality 211, these are my personal favourites.

With regard to the switching amplifiers, I feel if correctly implemented they can sound superb, its not just the bass control or the dynamics, its the ability to portray the interplay between the musicians with consummate ease, render the macro dynamic layering in a way that neither the others can, yet also produce the delicacy and imagery of say a 300B and drive virtually any speaker without fuss.

They also have a speed and liquidity if allowed to shown that will rival a quality valve amp design, I also find an intimacy they give I seldom hear elsewhere.

Are they valve sounding No, will they make you cry tears of joy listening to bespoke harpsichord music at low volumes with merest brush stroke of tonal thermionic colour, most likely not.

However they are no less capable of producing scintillating, engaging and fluid musical sounds that have a high realism factor.

We all take different aspects of music and make them our 'own' what is heaven for one chap is pure hell for another and vice versa.

In the same way they are quite shocking valve and solid state designs, there are very good ones too, the same applies to switching amps.

I personally use a self designed digital amplifier in my own system, I make refinements now and again, but to date I have heard nothing that would make wish to change.

 

I'm still not convinced that "we" can fully measure "everything". Most engineers/designers say that all cables sound the same, all pots, all caps..... but a few disagree, but lack measurements to "prove" it.
And then you get posts like this from John Westlake
"Each change had similar sonic effects, opening up the sound stage, more detail, increased Bass definition… of course non of these updates have ANY measured effect – but they have a huge effect on audio quality"
http://www.pinkfishmedia.net/forum/showpost.php?p=1192553&postcount=416

 

I think we all share some basic reactions or emotions when it comes to music -at least within our own culture.

For whatever reason, many audiophiles can't come to grips with the fact that a music reproducer just reproduces music and should be judged with the same standards used for live music. Perhaps it's too simplistic.

 

Two points.

Measurements aren't required to prove that that cables and pots sound different or the same. You simply play them to the group of listeners under blind conditions and look at the results. I've done this many times and have yet to find anyone able to make a selection that is more significant than pure chance.
Now, others claim to have done so which is fine. I want to see their tests - all of it including the process and until then I'll continue to be guided by what I've seen.

On Westlake, all but a handful of designers are simply too close to the fire to tell when the ambient room temperature has changed, if you get my drift.