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Old 3rd February 2011, 01:13 PM   #9401
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Any thoughts on how to build a sonically good ic op amp, or what is missing in existing ic op amp designs ?.

Eric.
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Old 3rd February 2011, 01:29 PM   #9402
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The mathematical model for cables of all types is one of the most well understood and highest correlation formula when compared to testing data we have. I'm referrig to the "Telegrapher's Equation." It gives the lump sum parameter equivalent of the distributed parameter network of a cable.
The lumped sum parameter equivalent is only an approximation. It pays no heed to the line length, prop velocity, or impedance mismatch at the load. While the equation is well understood, it's application to audio loads and frequencies is terribly mis-applied and mis-understood.

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The world standard for wire is Belden. There is nothing about wire that is known that Belden doesn't know.
I concur, Belden is the best. There is a lot however, that they do not know about wire. Try buying 75 thousand feet of low smoke, zero halogen, radiation resistant cable tray rated 2/0 single conductor...

And their papers on t-line theory use approximations..Still, they are the best out there.
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The aftermarket audiophile wire industry plays on ignorance, fears, and hopes of its prospective customers to sell solutions to problems that don't exist.
Or, possibly, problems that have not to date been discernable using standardized blind testing. I remain open to that possibility.

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The standard lump sum parameter description does typically not include dielectric properties.
Actually, they do for first order numbers. Specifically, the capacitance and cable impedance are. But second order effects such as absorbtion, no.

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Originally Posted by mrfeedback View Post
Agreed on Beldon - the beauty of Beldon is that their cable parameters are defined and guaranteed allowing predictable design and performance.Eric.
I do wish however, that they'd include inductance per foot for all their cable. They've been tending to include cable Z and cap per foot, and we have to re-calc to get the inductance.

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I am certain that there are audiophile speaker cables manufactured with such high shunt capacitance and poorly designed solid state amplifiers that are so unstable that the combination will form a tank circuit that will send the amplifier into spontaneous ultrasonic oscillation.
Actually, "poorly designed amplifier" requires some slight re-statement. If the amplifier is hot enough that tweeter unloading causes sufficient phase shift before unity gain, is it the designer's fault? The designer may have had speed/bw requirements that did not include stability in all regimes.. I would blame the one responsible for the initial design requirements.

Note I did not say excessive capacitance. It is because the tweeter impedance rises sufficiently well above cable z before unity gain. Cable capacitance is not the real culprit, but the load mismatch is.

Cheers, John

Last edited by jneutron; 3rd February 2011 at 01:41 PM.
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Old 3rd February 2011, 01:43 PM   #9403
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Many attribute it to arbitrary factors, but I think is is overlooked factors, not yet easily measured with test equipment made with the same electronics that we have already found wanting.
I am back after a short break, I see most of you seem to never take a break

Pavel,

If I measure the Cepstrum of a directly heated cathode vacuum tube amplifier without global feedback and a modern well designed solid state unit, do you think I would find time domain information that might show a difference?

ES
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Old 3rd February 2011, 02:02 PM   #9404
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Linn amplifiers will oscillate when driving capacitive cable.
Indeed their recommended cable is a heavy duty twin ribbon cable with conductors about 12mm apart - I suspect this cable is 300 ohm twin feeder cable for transmitter application.

Eric.
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Old 3rd February 2011, 02:23 PM   #9405
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Originally Posted by john curl View Post
This year at CES and The Show, a great deal of emphasis was placed on vinyl reproduction and vacuum tubes.
I take this as the high-end has given up trying to trickle down any of their ideas into more affordable mainstream products and has decided to serve their tiny market of followers with ever more ridiculously priced, as Kantor says, fetish objects.
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Old 3rd February 2011, 02:29 PM   #9406
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Quote:
Originally Posted by mrfeedback View Post
Linn amplifiers will oscillate when driving capacitive cable.
Indeed their recommended cable is a heavy duty twin ribbon cable with conductors about 12mm apart - I suspect this cable is 300 ohm twin feeder cable for transmitter application.

Eric.
Actually, the statement is only partially correct. The distinction is meaningless to the general public, as they normally have no control over the load characteristics at high frequencies. To people who do e/m for a living, the distinction is huge.

So..

Linn amplifiers will oscillate when driving a capacitive cable that is terminated in a load which decouples at higher frequencies.

A linn amplifier will NOT oscillate when it drives the exact same cable when that cable is terminated in a load which matches the cable impedance up to the unity gain point of the system.
Cheers, John

ps.. holy mackeral, that orange was horrible..red not much better...blue it is..

Last edited by jneutron; 3rd February 2011 at 02:32 PM.
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Old 3rd February 2011, 02:30 PM   #9407
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Originally Posted by jneutron View Post
Cable capacitance is not the real culprit, but the load mismatch is.

Cheers, John
The same might be said for speakers with regions of pathologically low impedance, the requirements for .1dB error from cable resistance might come into play.
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Old 3rd February 2011, 02:43 PM   #9408
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The same might be said for speakers with regions of pathologically low impedance, the requirements for .1dB error from cable resistance might come into play.
Agreed. Iff .1dB is of significance. Otherwise, it's just a number. When the termination impedance falls below line z, the system starts to look inductive. While I do have cases where inductance can cause instability, it's pretty much limited to load inductances outside consumer interest, anywhere from 5 to 70 henries.

What I am speaking of with hf instability however, is based in T-line theory. I do not have sufficient understanding of electronics to even think about a resistive divider...perhaps next semester??

ps..happy belated bday, you old guy...

Cheers, John
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Old 3rd February 2011, 02:52 PM   #9409
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Originally Posted by simon7000 View Post
Pavel,

If I measure the Cepstrum of a directly heated cathode vacuum tube amplifier without global feedback and a modern well designed solid state unit, do you think I would find time domain information that might show a difference?

ES
Ed,

most probably yes, how about interpretation of the result?

Regards,
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Old 3rd February 2011, 02:55 PM   #9410
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Originally Posted by Scott Wurcer
"I firmly believe that any man's finest hour, the greatest fulfillment of all that he holds dear, is that moment when he has worked his heart out in a good cause and lies exhausted on the field of battle - victorious."
Scott, I see you're you're all prepped for the super bowl.

Or are you just communicating the deeper meaning here?
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