John Curl's Blowtorch preamplifier part II - Page 1023 - diyAudio
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Old 27th February 2011, 06:20 PM   #10221
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Originally Posted by john curl View Post
Dave, as the 'designers' lead separate lives, so do people contributing to this thread.
As I have maintained for 32 years, through DIRECT EXPERIENCE, double blind testing of the ABX kind will NOT separate most of the passive components. ONLY long term testing will do this, and while it is NOT NECESSARY to peek, it is certainly a lot easier than to make a PERFECT switch-box. For what do I care whether a Roederstein or a Dale resistor wins a listening comparison? They both cost about the same. I have no stock or personal interest in EITHER company, and NOW in fact they are the SAME company, but they were NOT even in the same country, 10 or more years ago, when I first made my choices.
To my experience, many times long listening period is much better at evaluating the sound quality of components for audio system than short term swapping of components. More than once I liked a component at first audition, to find out its' shortcomings after a longer period of listening, some times a week or more.
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Old 27th February 2011, 06:24 PM   #10222
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Originally Posted by simon7000 View Post
30ua into 1 ohm = 30uv x 26 db gain = 600uv. 600uv into 4 ohms = .00000009 watts or -70 re 1 W.

Or try 30uv/2V = -96db. (I screwed up and forgot it's 6 db at 2 m not 3)
And 100 - 70 = 30.

So what does "100" represent here?

se
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Old 27th February 2011, 06:26 PM   #10223
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As I said previously, IF I tried to help an audiophile to improve an HCA3500 for example, people like Scott Wurcer would attack the very essence of my 'improvements'. Jan would require measurements, and SY would demand a double blind test. I might as well say this before anything is attempted. I am very serious in this statement, and I can back it up. This is why I often try to stay here on the 'straight and narrow' with design concepts that might bore PMA, but keep me out of trouble.
However, let me give you a 'proven' example of my modifications:
About 20 years ago, I designed my first power amp for Parasound. It was called the HCA-2200 MK 1. At the input was a dual fet input IC that ONLY allowed easy balanced to unbalanced input. I was elected to find the best IC for the job. I found the best IC that I could find, that met the specifications necessary. It had to be dual, minidip, unity gain compensated, and jfet input.
Measured good, however, independent reviewing of the product rejected the entire amp.
Now, if I were someone else, I would have 'blown off' the review, but being a little more experienced with certain problems, I decided to REMOVE the IC from the audio path. Guess what? It then got a 'B' review in 'Stereophile', and we were off and running. And that is the secret of my success!
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Old 27th February 2011, 06:39 PM   #10224
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Originally Posted by john curl View Post
As I said previously, IF I tried to help an audiophile to improve an HCA3500 for example, people like Scott Wurcer would attack the very essence of my 'improvements'. Jan would require measurements, and SY would demand a double blind test. [snip]!
Well, I can't speak for Scott or SY, but I I would hope you would want to come up with some measurements or arguments to support your improvements. Some arguments we could could follow as to why the change would be an improvement.
I mean, if you would say: change this R to 10k because it sounds much better, naturally I at least would ask why. I would ask: does it increase the slew rate? From what to what? Or does it increase the PSRR, by how many db? Or maybe it increases input stage linearity, how so? That's a reasonable technical discussion, that's something we (or at least I) learn from, things we can use to improve our own designs. Isn't that what you have stated as your goal? To help people how to improve their designs?

So please don't make it look as if you don't want to bring up changes because you fear the questions. Surely you have a good arguments for those changes? Then tell us.

jan didden
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Last edited by jan.didden; 27th February 2011 at 06:42 PM. Reason: sp
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Old 27th February 2011, 06:43 PM   #10225
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Yes, good idea and works well.
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Old 27th February 2011, 06:52 PM   #10226
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Well, PMA, your suggestion sure beat the IC approach. And WHY? Distortion? NO! Headroom? NO! Noise? Maybe, a little. I have been called a complete 'fool' by the 'Audio Critic' for using a jfet follower, instead of an IC. And so it goes!
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Old 27th February 2011, 06:58 PM   #10227
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Originally Posted by simon7000 View Post
So where it is possible to measure distortion quite accurately it is not as easy to determine under what conditions what level or type of distortion is actually perceived.


ES
But what if you don't measure its existance in the first place? If a signal chain has no 13th harmonic of 150Hz or whatever what is the point in arguing its audibility?
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Old 27th February 2011, 06:58 PM   #10228
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Then how about some documented facts? How about more than accolades or awards. How about.....technical proof!?........................................... .................................................. ..............Now about those facts.....


It's not so long since people here asked you for the same regarding claims which you made at that time...........they remain, as far as I can see, awaiting!

Why not be more reasonable and grant JC the same privacy you so clearly expect for your own ideas.
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Old 27th February 2011, 07:00 PM   #10229
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Yes, good idea and works well.
Micropower/Siliconix app notes from the 60's.
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Old 27th February 2011, 07:04 PM   #10230
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Jan,

......but what if the improvement produced inferior specs but sounded much better...........sometimes you can't qualify and quantify sonic improvements. I say that sometimes meters don't tell you everything.........if they did tube amps might have cease to exist decades ago.

Your humble student,

Jam
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