John Curl's Blowtorch preamplifier part II - Page 3282 - diyAudio
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Old 17th January 2013, 07:46 PM   #32811
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Quote:
Originally Posted by PMA View Post
AD797 will have high order harmonics somewhere at -125 or -130dB. Many of simple open loop designs will have it much higher accompanied by low order harmonics at -80dB or so. Again, such reasoning is funny and completely wrong and -130dB cannot be audible. If there is a reason of a different sound, it should be found somewhere else than at higher harmonics of -130dB.
Actually if you adopt the alternative 'Cherry' compensation that's in the AD797 datasheet, you'll see high order harmonics magically disappear .. IF the rest of your layout & circuit are up to scratch.

JC's measurements suggest poor decoupling and earthing. Too much concentration on Golden Pinnae bits and too little attention to basic principles.
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Old 17th January 2013, 08:11 PM   #32812
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Clifforest, that was NOT how it was, so far as I know. I seriously doubt that they even opened the case, BEFORE making their listening opinions. This is a MYTH, reverse engineered to EXPLAIN why they decided the amp was not 'ready'. (Direct quote)
The amp did NOT sound right, AND when we removed the IC, it sounded better. Not only with my amps, but with my associate Carl Thompson when we modified his unit. It got quieter, too. Maybe that was what it took. In any case, the MK2 was sonically better than the MK1, even if you just removed the IC and bypassed it.
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Old 17th January 2013, 08:12 PM   #32813
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MY MEASUREMENTS? Look to Samuel Groner! '-)
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Old 17th January 2013, 08:13 PM   #32814
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Originally Posted by john curl View Post
... any more than I have against American Cars.
JC,

We are going to disagree. Unless you are driving on a track or under weather conditions where the wise would not, the the performance value of a car changes. I go for comfort, safety, reliability, ease of parts and service, mileage and the ease of reading and using the controls.

I had 1,000,000 miles under my belt without a moving violation or accident. Until the guy driving the import hit me. I walked away (O.K. Limped because I did have my foot on the brake.) He didn't.

Attached is what my car looked like after. (No damage to the passenger compartment!)

ES
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Old 17th January 2013, 08:14 PM   #32815
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So what, PMA, they never listen.
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Old 17th January 2013, 08:15 PM   #32816
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Enjoy, Ed. '-) I don't have to pull trailers, and my autos are doing just fine.
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Old 17th January 2013, 08:55 PM   #32817
SY is offline SY  United States
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Quote:
Originally Posted by john curl View Post
MY MEASUREMENTS? Look to Samuel Groner! '-)
IOW, you have no relevant and comparative data to back up your assertions.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
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Old 17th January 2013, 10:51 PM   #32818
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SY, what do you want? I showed higher order distortion from a typical graph from Samuel Groner's measurements of the AD797, that has been discussed here before.
Admittedly, it is at a high output, but it does show higher order distortions.
It is almost impossible to measure the actual nonlinearity of an AD797 at low levels (typical working levels) because the high negative feedback and the residual noise floor hides it. This is also true with a CTC Blowtorch, but I DO have one advantage. Because I operate heavy Class A, I can predict the amount and order of distortion at low levels, mathematically, using the formula that 2'd harmonic drops directly with level, and 3'rd harmonic drops with the square of the level. Is this what you want?
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Old 17th January 2013, 10:55 PM   #32819
fas42 is online now fas42  Australia
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The arguments flow back and forth, back and forth, no progress is made. The point is, no matter how fussy you are with audio you will always hear distortion in the end result, for one reason or another. The electronic guys will point scathingly at the speakers and recordings as letting down the side, the recording guys will point scathingly at the quality and design of electronics in consumer gear as ruining their good work, on and on it goes ...

When the dust settles, everyone accepts that you always hear distortion in the end result. Otherwise, at least one system would sound identical to another one, , to the "worst" and "best" ears out there.

So, what do you do about it? Some people design and assemble gear so the "blessed" recordings -- yes, all the usual suspects -- sound "magnificent", and all of the lesser cousins sound relatively mediocre, or downright unlistenable to. They've adjusted, manipulated the distortion quotient, spectrum to suit their agenda, which is that only some source types and recordings are worth listening to.

There are many variations and versions of this procedure, tweaking the audible distortion pattern in numerous ways to get the "sound" they want ...

Me, I'm after making every album a powerful and emotionally rewarding experience to listen to, irrespective of how "good" the recording is. Which means that I manipulate the distortion also, happy to admit that, but at least I get the satisfaction when I'm listening to the music, I'm not aware of the system not being "quite right" when certain recordings are on. In my case I focus on reducing those distortions which particularly emphasise the inbuilt flaws of "lesser" recordings, and attempt to make the audible distortion invariant with the volume of playback -- go from headphone to PA sound levels with the "tonality" unaltered ...

My 2 cents worth, ...

Frank
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Old 17th January 2013, 11:12 PM   #32820
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What you appear to be seeking, Fas42, is the equivalent of an old Cadillac sort of design, or pure listening comfort, no matter what. This is a good direction, but it is not my direction in audio design. I want a revealing and clear, effortless design, not a super smooth design. I want the edges to show, and the hidden qualities of a recording to come out in an astounding way. That is different from your path.
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