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Old 19th January 2012, 04:33 PM   #1131
SY is offline SY  United States
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Quote:
Originally Posted by john curl View Post
It isn't 'peeking', it is keeping track of what source I am listening to, WHEN the music is continually changing. 'Peeking' implies actually seeing something and making some judgement from what one might see, but that is NOT the case, here. It is just having an A be an A, and a B be a B, so that I can decide whether I prefer A or B or if they both sound essentially the same. A computer could arbitrarily assign A and B, to two different products, and not tell me which is A or B. That would not matter.
Well then, all you have to do is tell A from B 8 times out of 10 (whether from preference or whatever) without peeking and you have something significant.
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Old 19th January 2012, 04:51 PM   #1132
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Quote:
Originally Posted by john curl View Post
If you listen and measure some amps built by the manufacturer for less than $500, you will have compromises that should be audible, including my own designs.
Not questioning that at all. Actually suggesting as clear differences can be heard, this may be a place to look to find objective measures that can be applied at the commodity as well as the higher end products.

So, if I buy an HCA 750, 1000, 1200, it should show me a clear step up? Provided they are new enough not to need re-capping of course. Not fair to compare less than as-designed. An A23 just is not in the cards with my wife still unemployed.
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Old 19th January 2012, 05:13 PM   #1133
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Quote:
Originally Posted by gaetan8888 View Post
Hello Wavebourn

Can you explain more about this test, with practical examples ?

Thank you

Bye

Gaetan
Here you go, from my Tower-III thread:

Quote:
Originally Posted by Wavebourn View Post
Here is 500 KHz 100V P-P response with 6N2P input tube, looks highly asymmetrical (for my taste). However, it is way above officially accepted audio band, but anyway it is a symptom that indicates presence of some non-linear phase shifts. Since subconscious sensitivity to phase shifts is 1,000 times better than a conscious one let's improve it anyway. The less of distortions we add is the better.

Click the image to open in full size.
Quote:
Originally Posted by Wavebourn View Post
Here is the same 100V P-P, 500 KHz square, but with 6N1P tube. Looks much better, except some overshoots. Now, even way beyond officially accepted audibility the amp performs much better:

Click the image to open in full size.
Quote:
Originally Posted by Wavebourn View Post
Here is the same, with 10 pF capacitor in parallel with 12K feedback resistor:

[img]Click the image to open in full size.
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Old 19th January 2012, 05:15 PM   #1134
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Another question D. Self can't answer only from a book.
He explains why I have never been happy with a passive preamp. FINALLY, a good technical explanation that passes the basic sniff test. But here is the question: If I follow a volume control with a buffer, have I done nothing but put the problem in the input stage of the buffer? Either I am missing something, or this is a case of not-my-problem.
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Old 19th January 2012, 05:23 PM   #1135
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If your buffer has more linear input resistance than D'Self's Blameless amp, consider the problem solved.
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Old 19th January 2012, 05:25 PM   #1136
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You may be educated, tvrgeek, but you lack a great deal in understanding differences in audio equipment.
From SY's point of view, virtually every solid state power amp should sound the same, and he can prove it with his 'scientific' tests. Yet, your wife seems very sensitive to different power amps. How can this be? This is for you to decide.
Now, what about Parasound power amps? Well, ANYTHING less than 1000, is NOT my design, and usually I have NO input to its parts selection or topology, unless someone in Taiwan decides to use what is already chosen by me for parts and decides to use a version of one of my topologies that I developed from 44 years ago.
The differences between the 1000, 1200, A23 should be trivial. This is because they have the same topology and parts selection (by me). The differences are age, price point, number of output devices, output power, power supply capacity, and to some degree, the amount of Class A region available.
I routinely use an HCA1000 for TV sound and I am happy with it. I would not use the HCA1000 for more critical listening, but it is pretty good for what it is.
The 1200 is just a bigger version of the 1000.
The A23 is just a newer version of the 1200 or 1500.
I hope, in future, to try an A21 for my home system. There is where the breakpoint should be.
In any case, it is important to make sure that the BIAS of the output stage is properly set. Often, many units come from Taiwan, are underbiased. The test is about 22-25mV across one of the emitter resistors, at idle (no signal) after warm-up (at least 1/2 hour). I test everything that I get for my own system for this, before listening.
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Old 19th January 2012, 05:36 PM   #1137
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Quote:
Originally Posted by john curl View Post
From SY's point of view, virtually every solid state power amp should sound the same, and he can prove it with his 'scientific' tests.
Nope, never said that. And wouldn't. See, for example, one of the papers I cited a few posts back, Carlstrom, David, Greenhill, Laurence, Krueger, Arnold, "Some Amplifiers Do Sound Different", The Audio Amateur, 3/82, p. 30, 31.
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Old 19th January 2012, 05:39 PM   #1138
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Quote:
Originally Posted by john curl View Post
From SY's point of view, virtually every solid state power amp should sound the same, and he can prove it with his 'scientific' tests.
That's bad faith, John. They are not his test and you know it. And dismissing a large body of research out of hand is also bad faith, or at least very closed minded. Did you even look at them?
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Old 19th January 2012, 05:58 PM   #1139
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John, yup. That is why I am hear to learn. A couple of books is not going to catch me up on 50 years of experience either, but they can help me jump over some wrong directions a lot quicker.

Much thanks so I did not fall for the comments on the legacy site for the slick sheet for the 750 "Influenced by" sure is not the same as "designed by" I'll start watching for a 1000 and for sure check the bias.

So, the question on the volume control is what provides a more linear input than the Blameless for a post volume buffer, LM4562? THAT1600?
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Old 19th January 2012, 05:59 PM   #1140
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This is not true, virtually every solid state amp is designed to be FLAT between 20-20,00KHz, deliver an essentially 'undistorted' output through that range, and the vast majority that we consider HI FI, manage to do so. So, what is wrong? Why doesn't everything sound the same to everybody? SY might quibble about changes in damping factor, etc, but really, these are small changes for most of us, AND we can verify that to ourselves just by adding a 1 ohm series resistor in series with the loudspeaker that we are listening to. TRY IT!
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