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Old 23rd December 2011, 10:22 PM   #41
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John Curl,
40 years ago or somewhat is when I as a young enthusiast spent many weeks pay on a Mcintosh receiver. Those were the days of true HI-FI. Big was always just a little bit too small. I would very much appreciate any link to the schematic of these great amps you have been discussing here in the last couple of days. Aside from major improvements in discrete components it seems the overall layout of a truely good amp has not changed all that much.
For me and others as do it myself types it would be nice to have someone with your experience relate to us exactly what is NOT needed in a good layout.
Nelson Pass uses the minimalistic approach which as an engineer I think reinforces the KISS principal. Do you adhere to this design approach or are certain key components necessary regardless of complexity.

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Old 23rd December 2011, 11:01 PM   #42
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Yes, to KISS, however, I like complementary balanced circuitry, as well.
"Condemnation without Examination is Prejudice"
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Old 23rd December 2011, 11:11 PM   #43
tvrgeek is offline tvrgeek  United States
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John, I can't remember the model. It was about 100W. 1400 or something like that. Mid 80's? I actually thought it was going to be the ringer as I grovel at your design expertise. I thought the really wide bandwidth and low TIM were maybe the key. But alas, she found it passed whatever bothers her and neither my little RA 840 or RB 941 Rotels do as much. They are not perfect, just more tolerable. It did rate just behind them ahead of my tweaked B&K and Haflers. As she liked ( in-store) the Cary tirode, I was wondering if my HK elite 300a would "filter" it, but no, it was far worse in her terms. My very worst amp is an 8W Chinese tube job I bought just to play with tubes. I learned a lot about tubes, but gad, what junk! I don't discount the possibility that her preference is the amp is NOT passing something bad in the recording, nor do I discount the possibility that even the best speakers are still so far being the electronics it is a matter of exposing a flaw.

In any case, there is a difference and I would like to measure it. Being an engineer (failure analysis for my lab days and now data architect) I still do like repeatable objective measurements that follow the laws of physics as least as far as Newton. I still have trouble with "spooky interaction at a distance" so I will let the good folks at the LHC figure out that one.

Sy is correct, best I can do is half blind and match with a fixed tone and DVM at the speakers. She can go into a store with someone else driving and do a no, no, no, OK, no right down the line. She is even more critical of the speakers. None of my own design have passed muster yet. The ML Squeal and good old Vandersteen were fine, but not tolerable in the living room. Veto on the Thiels over cost. She just tolerates my Paradigm Studio 20's with my own subs when driven by the Rotels. Whatever it is becomes a problem at just above conversation level. A great many speakers are totally unacceptable, but that is not localized to the amp differences. At least I can build subs low enough in distortion she enjoys full range music.

A few other hints. It does not matter if I use my modified NAD CD, my external Woulfson DAC, or my big Rotel CD payer ( also op-Amp changes). If I remember, I used my Denon SA CD player and external dac for the last tests as I have a pot on the dac and it has sufficient buffers to drive a real world cable. I can hear detail differences between them only through my Grado's with my own head amp. They sound the same to me through speakers. Whatever sets her on edge is not there.

On the Shefield "King James Version", second track when they really get with it, that is when it happens. I am not allowed to play any of my Buddy Rich very loud, but Chuck Majoine if fine. She has no trouble with live music, as in no PA system. I can correlate that with how bad the audience applause on Clapton unplugged is. It is a grade of horrible distortion, not good or bad. And again, I can hear some difference on the strings in several Julian Bream recordings. Not 100% correlation as the B&K, Haflers, and Parasound passed my test, just not hers. What I hear is the nylon strings take on a metallic overtone. I use Bream as my test standard as it seems to correlate more with the electronics that with the speakers. I would have thought my Paradigms being so mid level they would be the 800 Lb gorilla in the mix, but not so. They are good enough to make the issue audible.
Against those who think steady state THD is the cause, I am looking at a spectrum plot of my DH 120. At 1W out into a real speaker, I am measuring -93 dB third, and a good 5dB less for 4th and up. Far less than the power supply harmonics. ( new technology caps, rectifiers, etc on order). Another passing note, when I bought the B&K, it was the only amp I could find that passed the Bream test. A lot of really well known amps did not. I really liked the Aaragon but could not afford it back then. They still sell for too much 25 years on!

So, about all I can do is keep playing with amps on my bench and look for any difference. Once I can reproduce it, and if really lucky induce or remove it form a single piece of equipment. After 35 years, I have learned to appreciate her skill, but it still drives me crazy.

The one trace that I saw different was a difference between amps playing a half cycle pulse through a Seas tweeter picked up by my test mic into an e-my 1616. Monitored with my old Tek scope. I want to be able to capture it on the PC.
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Old 23rd December 2011, 11:34 PM   #44
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hey tvrgeek,

I have been a FOH engineer for quite a while. One thing I have found is that women like a more muted upper midrange than men, the sensitivity of the female ear is designed to key in on a crying baby, thus sounds that excite this instinct tend to distract women. I would suggest you look into this range to find what she is targeting.

On a similar note, people like what they are used to. One of my close friends can't stand my reference system as he likes the frequency rolloff of a standard 4" single wizzer sony boom box drivers and the distortion that goes with it. Thus I concluded measuring what is technically "right" may be wrong if it's not what a persons brain has defined as right. Everyones perception is different.
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Old 23rd December 2011, 11:36 PM   #45
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Some of Dr. Geddes papers on distortion:

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Old 23rd December 2011, 11:41 PM   #46
Francec is offline Francec  Australia
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My wife likes "radio" sound, that is, music played at a reasonably low volume on a crappy full range speaker. From my experience, so do many other women, so (if I'm brave enough to actually say it), you can't rely on a woman's (musical) judgement at all.

There you are, carte blanche to do what YOU like.
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Old 23rd December 2011, 11:45 PM   #47
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My wife says that I spoiled her tastes. She can't tolerate anymore stock Hi-Fis. She started hearing flaws...

Before that she used to play even boom-box.
The Devil is not so terrible as his math model is!
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Old 23rd December 2011, 11:57 PM   #48
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Opinion, FWIW-

All amplifiers with vanishing small distortion, flat response and DC-daylight bandwidth, while driving whatever load they're supposed to drive, sound identical.

Measurements of all sorts are essential to achieving those results and we lack nothing in the way of measurements in that frame of reference.

Speakers have far more characteristics to control and measure, but we don't lack much for measuring those as well.

The problem is that we keep targeting flat response, low THD and all the rest as desirable, yet my experience is that systems designed to those ends all sound about the same and all sound bad.

It seems the goal of high end is to sort of meet those goals to maintain credibility, yet deviate far enough to please the ear.

It would be really neat to do some kind of Monte Carlo test where everything was varied, opinions collected, and determine what the ear really wants to hear. All I know is that test bench perfection isn't it in a typical room with typical speakers.
I may be barking up the wrong tree, but at least I'm barking!
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Old 24th December 2011, 12:20 AM   #49
SY is offline SY  United States
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Conrad, have you read Floyd Toole's book? He does pretty much what you suggest.

I'm in 100% agreement that the speakers are far and away the weakest link in the chain given the paradigm of stereo. Compared with the sort of compromise we make sampling and compressing a dynamic 3-d soundfield into two spots, then sticking them in a different space, the worries about the electrical transmission path from transducer to transducer are truly weeing in the ocean.
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
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Old 24th December 2011, 12:43 AM   #50
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I came to this culture differently than most of the engineer types here. I started out as a theater sound engineer, didn't know much about how the gear worked. But much like a musician (i'm a classically trained musician as well) I learned to "play" a sound system. Part of this learning curve included watching an audience and learning what they liked. The interesting thing to me was that for each different audience the situation dictated a new data model to determine what kind of audience I had. I learned that gear that was high quality (sonically neutral) could be more adaptive than one that "colored" the sound. Although sometimes the taste of the audience was so extreme that a system had to be inherently biased, ska or hiphop for example, or I couldn't push the system hard enough in the frequency ranges that they liked boosted. While with a blue hair audience for a ballet a flat system was great. I could roll off any harshness and they would be in a relaxed place.

I guess what I'm trying to say is... Flat FR low THD is a good starting place, you can add distortion (EQ, reverb, echo, etc.) if you like but you can't take it away if it's inherent.

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