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post #31 of 39 Old 08-02-2012, 06:08 PM
 
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85 decibels is a few watts of power at the most. But like I said, believe whatever you want friend, but it's not exactly rocket science here. I know what distortion sounds like and this is not it, not even close.
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post #32 of 39 Old 08-02-2012, 06:14 PM
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If it's not rocket science, then why can't you give me a technical explanation for what's happening? rolleyes.gif

I'm an EE and I'm trying to help you figure out what may be going on. You know, to actually learn something instead of just hand-waving and attributing things to "synergy" and whatnot.

For every new thing I learn, I forget two things I used to know.
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post #33 of 39 Old 08-02-2012, 06:24 PM
 
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Well I don't think most people would have the 'technical expertise" to describe what's going on using your vocabulary as an EE. I've already described what's going on, the Emotiva amp I have, an XPA-3, is bright or forward at high frequencies at higher volumes. The Parasound amp, being high bias Class A among other things designed by John Curl, is not. Therefore, with my speakers, it sounds different than the Emotiva. You may want to throw this all out as voodoo though.
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post #34 of 39 Old 08-02-2012, 06:30 PM
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Somehow I think you have mis-read my "voodoo" comment and have gotten offended when that wasn't my intent.

I'm actually taking your observatons about the differences at face value.

What I'm saying is "voodoo" is to attribute these differences to things like "synergy." That has no meaning, to an EE or to anybody who thinks critically. I was trying to dig a little deeper and find out what is really going on.

In other words, think of it like this: If there is indeed an audible difference, then is must be measurable. So what parameter would account for this difference? Clipping could. A change in FR with level could, though that would be a strange thing to come upon in an amp that was running below clipping. There are probably some other explanations as well.

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post #35 of 39 Old 08-02-2012, 06:31 PM
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Save your energy and enjoy your S6s. They and Halo are awesome! Not everyone can experience those.
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post #36 of 39 Old 08-02-2012, 07:46 PM
 
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Quote:
Originally Posted by beaveav View Post

Somehow I think you have mis-read my "voodoo" comment and have gotten offended when that wasn't my intent.
I'm actually taking your observatons about the differences at face value.
What I'm saying is "voodoo" is to attribute these differences to things like "synergy." That has no meaning, to an EE or to anybody who thinks critically. I was trying to dig a little deeper and find out what is really going on.
In other words, think of it like this: If there is indeed an audible difference, then is must be measurable. So what parameter would account for this difference? Clipping could. A change in FR with level could, though that would be a strange thing to come upon in an amp that was running below clipping. There are probably some other explanations as well.

I hear you, but what you are trying to do is find an alternative culprit for what I am hearing. It seems you don't believe two different amps can sound somewhat different. Do you believe all speakers sound the same if they measure the same? Because all speakers basically measure the same.

I am satisfied that when two amps are auditioned in the same system, in the same room, at the same decibel level, and one amp sounds different than the other, then it is different. But I appreciate those who feel otherwise, that is what audio is about after all.
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post #37 of 39 Old 08-02-2012, 08:18 PM
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Quote:
Originally Posted by beaveav View Post

"That has no meaning, to an EE or to anybody who thinks critically. I was trying to dig a little deeper and find out what is really going on.
In other words, think of it like this: If there is indeed an audible difference, then is must be measurable. So what parameter would account for this difference? Clipping could. A change in FR with level could, though that would be a strange thing to come upon in an amp that was running below clipping. There are probably some other explanations as well.

An EE would understand that driver impedance interacts back with the amplifier. A varying voltage level, presented to a basic solid state amplifier can result in current deficiencies at several frequencies, which has the potential to impact the end result that you hear. Especially in regards to bass, and often in "soundstage".

Amps measuring the same on a test bench is not a test of "sound". Amps must be hooked up to an infinitely varying load, aka the loudspeaker.

The most obvious correlation is a comparing two different cars traveling on a concrete road. Everyone would acknowledge that both a Ford Fiesta and a Ferrari 458 Italia can easily drive at 100mph on a concrete road. But change that road to a 35degree upward angle (aka a loudspeaker with a difficult Ohm rating), and the Fiesta may never get to 100mph, even though it is designed to got that "fast", i.e. 100wpc.

If you don't hear any difference between amps, that is cool. There are several amps that sound the same to me, too. But to argue that all decent amps measure the same is ignoring the fact that the amp THD distortion measurement, etc., is only one-half of the measurement equation.
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post #38 of 39 Old 08-03-2012, 01:30 PM
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What the??

Is your post supposed to make sense? Because it doesn't.

What is an "infinitely varying load" exactly?

What are current deficiencies? Is that different from clipping somehow?

And your analogy is, well, a stretch, a reach, to put it politely.

And when did I say all amps sound the same? A more careful reading of this thread would tell you that I took his word that his two amps didn't sound the same. I've done blind tests and found amps that did not sound the same. But that's not the point. The point is that when they don't, there's a real reason for it, a technical explanation in there somewhere. And I'm fully well aware that THD is but one of those possible reasons. I test consumer audio equipment for a living. THD, linearity, freq resp, SNR, IMD, source impedance, etc, etc....

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post #39 of 39 Old 08-03-2012, 04:36 PM
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Contributing to one of these threads is like watching a train wreck; you don't want to watch but can't look away.

Major things I have found to make a difference among amplifiers:

1. Difference in amplifier gain; louder usually sounds better. Modern AVRs and tight gain-matching can alleviate much of this as a factor when listening but worth checking. I think the trim steps tend to be a little coarse so even running your AVR's setup might not completely negate this effect.

2. Output impedance; makes the amplifier dependent upon the load. This is one of those things that can matter at all power levels, and is perhaps the biggest difference between tube and solid-state amplifiers. It changes the FR etc.

3. Charge storage, and related abiity of the output stage to deliver it. Amps with little charge storage may suffer on large LF transients. This is not usually an issue at lower volume, however.

4. Noise level; some amps do exhibit more hiss/noise. This rarely matters once the music (or movie) is playing.

5. The ever-popular perception and bias factors. Bigger, heavier, more-expensive amps almost always win in a sighted test.

The first four are not too hard to measure, but (2) and (3) require sweeps with realistic loads (preferably in-system with the user's speakers) and material so are not usually seen in a magazine review. I wish there was more pulse and other time-domain testing done, and with a variety of more realistic loads. I did leave off raw power ratings as too obvious; a 10 W amp driving 80 dB sensitivity speakers in a big room is likely unwise.

Onwards - Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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