Teddy Ray
pfm Member
The carbon and charcrofts all measure the same.
bet you couldn't id them blind. im certain of it, actually.
The carbon and charcrofts all measure the same.
I think that's a fair enough challenge which deserves a reply. If two amps can be shown to be audibly different in blind ABX testing by being distinguishable in a significant number of cases I would expect one or all of the following measurements to show a difference, all other things being equal: output signal demonstrably different for a given input music (not test) signal - perhaps detected by differencing the outputs; output signal different for pink noise, ditto; difference of input to output detectably different; amplitude and phase spectral response detectably different; impulse response detectably different; harmonic distortion detectably different; clipping distortion detectably different.My point, if anybody decides to take it up, is that lots of people on here advocate measurement, but actually correlating those measurements to what we hear isn't something that anybody on here has yet ventured to try.
So, how can these advocates of measurement uber alles support their POV, unless they can be sure the measurement correlates to musically relevant criteria?
Assuming they can, I'm interested to know what might be the normally accepted values and the minimum increments which might be considered relevant or audible.
Relying on numbers, without being to explain why they are relevant, is no more valid that relying on purely subjective opinions and totally disregarding the numbers.
So, how can these advocates of measurement uber alles support their POV, unless they can be sure the measurement correlates to musically relevant criteria?
To my mind amplifiers can not be considered in isolation from their intended operating environment - they are a tool one selects for a very specific role, so any attempt to generalise with a few simple specs is largely an irrelevance. The real world is very different.
Power supply stiffness, noise and rejection seem to matter too, but I'm not sure how these materially affect the transfer function of an amplifier, pre or power.I think that's a fair enough challenge which deserves a reply. If two amps can be shown to be audibly different in blind ABX testing by being distinguishable in a significant number of cases I would expect one or all of the following measurements to show a difference, all other things being equal: output signal demonstrably different for a given input music (not test) signal - perhaps detected by differencing the outputs; output signal different for pink noise, ditto; difference of input to output detectably different; amplitude and phase spectral response detectably different; impulse response detectably different; harmonic distortion detectably different; clipping distortion detectably different.
I think that's a fair enough challenge which deserves a reply. If two amps can be shown to be audibly different in blind ABX testing by being distinguishable in a significant number of cases I would expect one or all of the following measurements to show a difference, all other things being equal: output signal demonstrably different for a given input music (not test) signal - perhaps detected by differencing the outputs; output signal different for pink noise, ditto; difference of input to output detectably different; amplitude and phase spectral response detectably different; impulse response detectably different; harmonic distortion detectably different; clipping distortion detectably different.
The situations where those additional considerations arise are however few and far between, and generally covered by the usual rider that amplifiers should not be driven into clipping.
Perhaps with valve amps, but a "proper" solid state amplifier should approximate a true voltage source, and double its power into halving impedances - is what I expect to be one parameter that serge would look for. Krells can do that, but I rarely hear them espoused for "musicality", whatever that means.... given the current fashion for very small ported two way stand-mounts which makes for some remarkably inefficient and hard to drive loudspeakers e.g. low 80s sensitivity and sweeping reactive loads with severe impedance dips and spikes. A lot of very highly regarded amplifiers will respond to that in audibly differing ways.
Perhaps with valve amps, but a "proper" solid state amplifier should approximate a true voltage source, and double its power into halving impedances - is what I expect to be one parameter that serge would look for. Krells can do that, but I rarely hear them espoused for "musicality", whatever that means.
Thanks. Are these measurements routinely published by the manufacturers, perhaps available on their websites? I can't say I've seen them, as a rule.
If not, do those people who advocate measurement (I'll exclude Serge, as I think I know the answer) measure these parameters for themselves? If so, before or after purchase?
You did, by the way, forget to answer the bit of the question about by how much these parameters would have to change, to be audible, or to produce the sort of musically relevant effect I described.
My point, in case it has passed anybody by, is that reading the numbers on a makers bumf might make it possible to conclude that two amplifiers are different, if their numbers are different. But being able to read those numbers and draw anything other than general conclusions about them seems either unlikely, or (perhaps) beyond the technical capabilities of some of those who espouse these views.
I'd hazard a guess that those on here who can genuinely interpret the measurements, decide which ones are critical and how (and by how much) they would need to change to achieve an audibly different result, are in a very small minority. What's more, I have my doubts that those are the ones (Serge excepted, perhaps) who would advocate such an approach.
If so, I think that choosing your amp by the numbers without being able to defend the decision by explaining what those numbers mean, compared to an amp you disregarded, starts to look less like science and more like numerology. In other words, it's a subjective impression of whether you like the look of the numbers not a rational scientific one.
Perhaps with valve amps, but a "proper" solid state amplifier should approximate a true voltage source, and double its power into halving impedances - is what I expect to be one parameter that serge would look for. Krells can do that, but I rarely hear them espoused for "musicality", whatever that means.
Perhaps with valve amps, but a "proper" solid state amplifier should approximate a true voltage source, and double its power into halving impedances - is what I expect to be one parameter that serge would look for. Krells can do that, but I rarely hear them espoused for "musicality", whatever that means.
I don't think being able to go down to 1-ohm whilst maintaining full drive voltage is necessary unless driving Apogee Scintillas. Any amp that gets close to doubling their 8-ohm power into 4-ohms is good enough for most nominal 8-ohm loudspeakers, which shouldn't dip much below 5-ohms at minima. They can get into trouble with 4-ohm designs though, which is favoured by American designers and hence the need for arc-welding amperage.I don't think any UK amp manufacturer has a product that correctly doubles output as impedance halves, especially to Krell level where the amp is able to do it right down to 1 Ohm IIRC. If you want accurate that is what it looks like, anything else is compromise.
Can I just digress slightly in the opposite direction?
Let us assume, for the sake of argument, that we have a pair of amplifiers on which there is general agreement that they sound different. We may then assume and agree that they will measure differently, too.
To suggest a difference: one amplifier is more exciting and involving than the other. The music sounds more dynamic, the musicians sound more skilled and committed to the music, their sense of timing and pitch is more obvious and 'right'. Everything is just much more enjoyable and fun to listen to.
Assuming that the nominal power output is the same for both, what other parameters could be 'in-play' here, and what sort of difference in the values of those parameters would be necessary, or indeed audible?
Yeah, OK, so we've established that avole doesn't know, but what about any of the other techy types out there?
seem quite odd that all these people who claim all amplifiers, dacs, cd players etc all sound the same never seem to use the cheapest brands and units available.
Generally not I would say, although most or all of them would have been measured by the manufacturer in development and some used as routine end-of-line tests.Thanks. Are these measurements routinely published by the manufacturers, perhaps available on their websites? I can't say I've seen them, as a rule.
I have no idea, but I suspect not. I don't.If not, do those people who advocate measurement (I'll exclude Serge, as I think I know the answer) measure these parameters for themselves? If so, before or after purchase?
I don't know. As I've stated a couple of times, in many cases we don't know at what level different measurable results become reliably audible for different classes of listener, and the question is complicated by the fact that you can't generally give a single number for any measurable. It often depends. However there are some generally accepted limits as Serge has pointed out and many real world amplifiers measure way below them. Having said all that, it is not my view that we can say with confidence what measurable effect will be audible and what will not, particularly near to the threshold. My position is complementary to your question: which is that if two amplifiers can be shown to be audibly diferent then they will measure different to an extent that plausibly explains the audible difference - I do not accept the idea that we can hear things that result from unmeasurable differences.You did, by the way, forget to answer the bit of the question about by how much these parameters would have to change, to be audible, or to produce the sort of musically relevant effect I described.
But what people are claiming isn't that you choose your amp on the basis of the maker's bumf. They are saying that, assuming you don't have some exotic speaker which presents a bizarre load, any competent SS amplifier working within its operating range will be indistinguishable - then all you need to decide is what the efficiency of your speakers is and how loud do you want to go. Not necessarily my view, although I do think that the amplifier in most systems has the least effect on the performance of the system as a whole, compared to sources and speakers, to the point of no difference to my cloth ears. I do agree however that choosing your amplifier by comparing THD+N figures in manufacturers' glossies makes no sense.My point, in case it has passed anybody by, is that reading the numbers on a makers bumf might make it possible to conclude that two amplifiers are different, if their numbers are different. But being able to read those numbers and draw anything other than general conclusions about them seems either unlikely, or (perhaps) beyond the technical capabilities of some of those who espouse these views.
I'd hazard a guess that those on here who can genuinely interpret the measurements, decide which ones are critical and how (and by how much) they would need to change to achieve an audibly different result, are in a very small minority. What's more, I have my doubts that those are the ones (Serge excepted, perhaps) who would advocate such an approach.
If so, I think that choosing your amp by the numbers without being able to defend the decision by explaining what those numbers mean, compared to an amp you disregarded, starts to look less like science and more like numerology. In other words, it's a subjective impression of whether you like the look of the numbers not a rational scientific one.
An amp suitable for the Scintilla will be ideal with the others, but a gratuitous waste of resources.Tony L said:A Quad 57, Linn Isobarik, Apogee Scintilla, Lowther and Klipschhorn are all very fine loudspeakers, some of the very finest in fact, yet so different from one another as to have different and often contrary input requirements. Differences in efficiency, loading, current demand and mechanical damping of these speakers is so extreme as to require entirely different amplification solutions.
There's a misconception here. There are two conditions, the boundary of the output of the amp, so the maximum power an amp will produce into various loads, you will seldom find a true voltage source here because of PSU limitations, unless the amp is nobbled into higher impedances, which I'm sure happens in dark corners of the high end market. The other is the output impedance of the amp which applies all the time and will never be 0, although nowadays it will be low compared to the wiring.James said:Perhaps with valve amps, but a "proper" solid state amplifier should approximate a true voltage source, and double its power into halving impedances