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Old 30th November 2012, 02:18 PM   #30501
Bonsai is offline Bonsai  Taiwan
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Quote:
Originally Posted by john curl View Post
Trivial explanations like 'oscillation' or change in capacitance are pointless. We know how to check for these things, we also know how to protect an audio product from being sensitive to small changes like capacitance. It is called 'engineering'. '-)
Well then apply some of that engineering John. Maybe a first step in ths direction would be for you to include an isolating inductor and Zobel network on your amplifier output.
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Old 30th November 2012, 02:24 PM   #30502
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We have Zobel networks already. Perhaps you should understand that it is in INTERCONNECT and INTERNAL HOOKUP WIRE that I am most interested in differences. I haven't changed my loudspeaker cable for the last 15 years.

Last edited by john curl; 30th November 2012 at 02:36 PM.
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Old 30th November 2012, 02:35 PM   #30503
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Bonsai, please note Zobel network:
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Old 30th November 2012, 03:08 PM   #30504
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Originally Posted by john curl View Post
We have Zobel networks already. Perhaps you should understand that it is in INTERCONNECT and INTERNAL HOOKUP WIRE that I am most interested in differences. I haven't changed my loudspeaker cable for the last 15 years.
Well then perhaps you should speak to somebody who devised a wide bandwidth test of amplifier susceptibility to IC ground loop currents? One which is capable of in situ sensitivity testing as opposed to benchtop tests which do not generally provide identical ground loops.

You know...something like this..

ps. With amp and pre on of course, monitor output of the amp.

Granted, it does not really work the amp supply wires, line cord wires, but hey, ya gotta do it one step at a time, right?

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Old 30th November 2012, 03:12 PM   #30505
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JN are you telling me that the difference between quality and average wire is the tendency toward ground loops? '-)
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Old 30th November 2012, 03:18 PM   #30506
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jn - I like this idea for a test very much. May I PM you to get more details? Its similar to the kind of things I've been banging on about on various boards for a couple of years on and off but don't gain much traction.
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Old 30th November 2012, 03:20 PM   #30507
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If you choose to continue, I recommend you learn enough t-line theory to understand the analysis. I unfortunately lost the testbook I used back in '74 or '75, perhaps somebody else can chip in with a reasonable text...certainly not Jackson or Becker...


Read above.
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jn, Bob I'm somewhat disappointed in your exchange, I would still like to observe these effects first hand but it is difficult. As for audibility I'm afraid my ears are not up to it.
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Old 30th November 2012, 03:31 PM   #30508
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Originally Posted by jneutron View Post
Well then perhaps you should speak to somebody who devised a wide bandwidth test of amplifier susceptibility to IC ground loop currents?
My efforts is always to get as little HF contamination at the power amplifier output as possible. Measured in a whole audio chain. Wideband measurement and reduction of HF contamination by circuit design, shielding, grounding, wiring, PSU design, everything that matters. Reduction and minimization of HF contamination goes hand in hand with resulting "sound quality".
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Old 30th November 2012, 03:31 PM   #30509
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Quote:
Originally Posted by jneutron
http://www.belden.com/docs/upload/Pr...les-Part-1.pdf

If you look at page 1, they show a graph on the right hand side.
Thanks for providing the link. As you say, it illustrates what I have been saying. On the left side there is the equation for propagation constant, which may answer Esperado's question.

Quote:
If we adopt DF96's numbers, the mismatch is no longer 75 to 4, but 250 to 4. That requires even more reflections.
Be careful. At lower frequencies the line may have greater attenuation because a greater proportion of the series impedance is made of resistance. As I have said, your method and my method, if applied fully and correctly, must provide the same result as your impulses synthesise my audio waveform. Any deviation will be due to different approximations being used. The net result will be a small time delay and a small audio phase shift.
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Old 30th November 2012, 03:41 PM   #30510
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JN are you telling me that the difference between quality and average wire is the tendency toward ground loops? '-)
No. I am saying that if a system's sound changes as a result of an IC swap, before one begins to invoke pseudophysical explanations or even misappropriated physics explanations, one must first look at the obvious.

You yourself had this issue when you were testing IC's on your equipment. Through careful repeated testings and trials, you found that cleaning your rca's thoroughly had an effect on your results. That is a classic groundloop behaviour. You also mentioned horiz scan intrusion as well, another classic ground loop problem.

Others have reported moving IC's back "into position" to modify a system sound. Another classic ground loop problem.

Power cord, same thing. That's why I include the power cords and duplex outlet in my test.

The materials choice for an IC will indeed alter the loop currents and how the signal return currents travel.

Amplifiers and sources which are susceptible to either creating ground loop currents, or responding to them are the primary smoking guns when it comes to ground loop issues. My test is to identify the sensitivities.

I include the source/preamp as well because it is part of the loop and can be sensitive that way. Whitlock, to the best of my knowledge, ignores outputs in his pin 1 tests. That is an error.

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Originally Posted by abraxalito View Post
jn - I like this idea for a test very much. May I PM you to get more details? Its similar to the kind of things I've been banging on about on various boards for a couple of years on and off but don't gain much traction.
Sure. Or, on forum. Perhaps this thread since JC is interested?

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jn, Bob I'm somewhat disappointed in your exchange,
I am extremely disappointed. Both in how he brushed it all aside, and how I handled it..

jn
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