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Old 16th December 2012, 11:48 AM   #7841
AndrewT is offline AndrewT  Scotland
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The missing pics in post7832 come back with
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I can see pics in post7836
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Old 16th December 2012, 04:54 PM   #7842
bcarso is offline bcarso  United States
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We are also supposing that the HFN/RR measurements are accurate, and that the amplifier was not oscillating into some strange load, or as the result of some bogus connections. Note that the only inputs are balanced, and perhaps the output is also. No mention is made in the sidebar of the test equipment used, although as I'm only a sporadic reader of the magazine maybe they disclose this sometimes, and it is always the same. Again, although Stereophile isn't perfect, it does make me appreciate them by comparison.

I haven't been a close reader of Krell specs in previous reviews, so I have no idea how they tended to run in terms of signal-to-noise. I only picked up anecdotally that they are powerhouses in terms of high current --- in fact weren't they initially developed to support some very-low-Z and inefficient ribbon speakers --- were they ones from Apogee?

Actually I find a lot of highly-touted equipment to have disgracefully high noise, so I am not singling out this latest effort from D. d'A. When six of us were still cooperating in a speculative class D amp effort and about to go to a tradeshow, it was impossible in the short term to find a digital source low-enough-noise to have the power amplifier noise dominate. People remarked as to how the noise at the fairly-efficient speakers was virtually inaudible, even with the ear pressed up against, and I reminded one of the consortium that it was strongly dominated by the Bel Canto DAC, loaned to us along with the big speakers by Andrew Jones. That itself had replaced the (iirc) Simaudio piece, which was much worse for noise.

As I say with respect to the reviewed amp, I'm just puzzled and curious. I am even tempted to speculate about the conscious use of stochastic resonance, although the effectiveness of that will be very loudspeaker-efficiency-dependent.
Apropos of amplifier noise, see the fascinating review of the Devialet D-Premier in the January 2013 Stereophile. JA does both the listening and the measuring, and although he is very enthusiastic about the product, his measurements are difficult to reconcile with the manufacturer's claims, particularly of a S/N unweighted of 130dB (no reference level given, but the max power is specified at 240W into 6 ohms, for which I calculate just under 38V rms).
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Old 17th December 2012, 01:34 PM   #7843
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If a spec is bad yet not to the point of disaster could it be a choice ? Certainly it would have a masking effect . If the spectrum was pinkish I would be especially interested . This is so fundamental as to look suspiciously like a choice . I spend most of my life measuring noise and saying to myself how good do I need this to be . For me it is impossible to beleive an engineer can make a mistake over this . Many circuits I design aspire to 78 dB ! I think someone said the electrons are counted in how many per second passing not how many million when the signal level is 100 uV . I sometimes use carbon composition resistor for inputs . They are not good on measurements . This becomes a non issue when the pre amp is connected . Strangely although the measurements become acceptable in real life with a pre amp shunt the sound is non the less changed . I do not like CC resistors . However I like them more than other cheap ones . Tyco non inductive are my favourites , $8 in bulk a piece . I am told pulse lasers keep the production of cheap CC resistors going .
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Old 17th December 2012, 05:00 PM   #7844
dvv is offline dvv  Serbia
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I obviously do not believe specs can tell us much about the sound of anything.

Specifically, the spec on noise: I have had the opportunity many a time in life to hear devices with brilliant specs which didn't sound all that good at all, as well as devices with very humble specs which sounded brilliantly. "Humble" means at or just below par with its respective price class average, not as Nige says disasterous.

What I heard the least in my life were power or integrated amps which interfaced well with ahything I chose to call a speaker. One such item is the H/K 6550 integrated amp, despite its relatively modest power output of 50/70 Watts into 8/4 Ohms - BUT, it does its thing into everything I ever threw at it, both at home (AR94, JBL Ti600, B&M 1041 Monitor) and outside it. I am not saying it loved them all equally, but I am saying that the difference was surprisingly small, and double surprisingly in view of its relatively low price.

While some of its competitors, with much better specs, fared much worse. The fact that they had better S/N ratios didn't do them any good.
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Old 17th December 2012, 05:19 PM   #7845
a.wayne is offline a.wayne  United States
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Sometimes brilliant specs dont sound right due to the addition of distortion from other components in the chain and seeing such , the best solution is not always where the light is ..
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Old 17th December 2012, 06:02 PM   #7846
dvv is offline dvv  Serbia
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Sometimes brilliant specs dont sound right due to the addition of distortion from other components in the chain and seeing such , the best solution is not always where the light is ..
For whatever reason, great specs by no means guarantee good sound.

The number of possible reasons for this is impressive.
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Old 17th December 2012, 10:12 PM   #7847
fas42 is offline fas42  Australia
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Excellent specifications are only meaningful in the context of a complete, working system -- and measured over a wide range of operating conditions. Otherwise, it will just lead you astray.

It's as simple as, how strong is a chain? As strong as the strongest link, the average of the strengths of all the links, or precisely that of the weakest link(s). Strangely enough, , for me I've found it to be always the last scenario, so the answer has been to work out which were the dodgy ones, even if they were boring as hell, no bling or pizzaz associated with them whatsoever, and sort them out ...

Frank
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Old 18th December 2012, 07:26 AM   #7848
dvv is offline dvv  Serbia
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Frank, the weakest link always defines the strength of any chain. Not only for you, but for all of us, always.

I agree on specs being meaningful in a complete system, but even so, they tell only a small part of the story.
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Old 18th December 2012, 09:52 AM   #7849
fas42 is offline fas42  Australia
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I agree on specs being meaningful in a complete system, but even so, they tell only a small part of the story.
The trouble is, no-one is doing it for complete systems, which means, measuring various performance parameters for the complete path from the source file through to the output of the speakers. Under a variety of circumstances, for a range of testing material. Yes, this is all going to be difficult, good microphone capture techniques will necessary and highly capable software to crunch the results, comparing the output to input. But, if the bullet is bit, then I'm sure the results will be extremely illuminating; you will, for example, discover how the distortion varies depending on the usual things that people fiddle with, in their tweaking.

And I believe it will tell a very large part of the story ...

But of course all this is too hard, too messy, too everything, so it won't be done ... probably ever. So the audio fraternity will continue to circle each other, taking odd pot shots at each other's point of view, and no progress will be made, c'est la vie ...

Frank
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Old 18th December 2012, 11:15 AM   #7850
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For whatever reason, great specs by no means guarantee good sound.
To me, "great specs" (ie, measurements, high fidelity) is a defined characteristic.
"Good sound" (ie, sound quality, colloquial hi-fi) is not.
So the jockeying is evidently not as logical as it is inevitable.
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