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Stereophile Tests $45k D'Augostino Monoblocks

Ron Texas

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jtwrace

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Stereophile and @John Atkinson never cease to amaze me. One would think that this amp was measured before sending it so this wouldn't even be an issue. On top of that, once discovered; it would be sent back to the manufacturer and perhaps confirmed before publishing with a question mark? Pathetic.

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audio2design

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PierreV

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In fairness, if one is fluent in Atkinspeak, the measurement part was clear enough.

His defense of JVS, otoh... If the biasing slowly drifts in use, it even worse than the usual "something mysterious must have happened during transport".
 

franspambot

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Remember when the Audiophiliac wrote a review for Stereophile?

"Overall, I would say that the JitterBug eliminated what I described as the "ethereal" character of computer audio, bringing it very close to what I experience from spinning CDs.

You can see from the "Measurements" sidebar that I could find no significant effect that the JitterBug had on the analog signals output by three of the DACs I had to hand. Yet with those DACs and others, I heard an improvement in sound quality that I can attribute only to the JitterBug. I hate when that happens!

Last June, Michael Lavorgna wrote that "measurements obviously have no direct correlation to enjoyment." I have no hesitation in declaring, loudly and longly, that I can think of no way to spend $49 that would make me more enjoy my computer-based audio than the AudioQuest JitterBug. Try one—or two—for yourself."

Oh wait, that was Atkinson. Why does anyone here act surprised when they trip over themselves?

Just in case: I was dumb enough to buy one of these things. (It was reviewed here, lol.) If anyone wants another worthless anecdote: it did f-all.

 
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LTig

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It's just ridiculous. Mr. D'Agostini is cited that the amp runs up to 100W in class A before it switches to AB, to prevent crossover distortion. However measurements reveal tons of them while standard class AB amps show nothing due to proper biasing and negative feedback. Maybe the designers should read Douglas Self's power amplifier design book where he shows via simulation that more quiescent current than the small optimum value increases distortion.
 

sarumbear

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Stereophile and @John Atkinson never cease to amaze me. One would think that this amp was measured before sending it so this wouldn't even be an issue. On top of that, once discovered; it would be sent back to the manufacturer and perhaps confirmed before publishing with a question mark? Pathetic.

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View attachment 160361
Firmware code on an analogue class AB amplifier!

and, Atkinson doesn’t even question the absurdity of the comment. Thank God that we have ASR.
 

MakeMineVinyl

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Firmware code on an analogue class AB amplifier!

and, Atkinson doesn’t even question the absurdity of the comment. Thank God that we have ASR.
I write firmware code for all our amplifiers, some of which can control the analog path, so its not unusual and I suspect many manufacturers do this. But at least I check my fucking code before any unit gets to the prototype stage. :facepalm:
 

Matias

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Well at least he admits he is not chasing numbers anymore as in his Krell days, and now he is tuning by ear. Literally adding euphonic distortion. Just like Nelson Pass does.
 

Drengur

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Well at least he admits he is not chasing numbers anymore as in his Krell days, and now he is tuning by ear. Literally adding euphonic distortion. Just like Nelson Pass does.
This is very positive. It gives people like me hope. What has been standing in my way from being a top notch electronics engineer is all this pesky 'science' and those humdrum tests. My designs are all quantum entangled and full of deep learning predictive analysis because that gives air and velvety texture to the music (organ music on vax cylinders).
 

Robin L

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This is very positive. It gives people like me hope. What has been standing in my way from being a top notch electronics engineer is all this pesky 'science' and those humdrum tests. My designs are all quantum entangled and full of deep learning predictive analysis because that gives air and velvety texture to the music (organ music on vax cylinders).
"I'm signing you up for extra medication."
 

Galliardist

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The oddly measuring amp and the review sample - two out of three - had bias issues, and for tbe review sample at least it was audible.

I note that tha measured amp was tested in the factory. Now, I’d assume that the distortion at 5W into 8 Ohms would not have got past that check? After all, it would have failed QC at tbe Leak factory in tbe mid 1950s…

So the conclusion would be that this amp can suffer from serious bias drift in a very short time in use?

As an aside, I wouldn’t expect an amplifier at this price to invert polarity, either.
 
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PierreV

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So the conclusion would be that this amp can suffer from serious bias drift in a very short time in use?

Maybe. More probable that JA put his foot in his mouth to defend JVS' ears. In any case, if the amplifiers drift freely, they shouldn't be on the market or should be with a potentiometer to tune the bias ;)
 

sarumbear

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I write firmware code for all our amplifiers, some of which can control the analog path, so its not unusual and I suspect many manufacturers do this. But at least I check my fucking code before any unit gets to the prototype stage. :facepalm:
How does a firmware control an analogue signal path?
 
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