John Curl's Blowtorch preamplifier part III

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#20,602
DF96 said:
Yes, of course. However, few people here (or anywhere else) have superconducting audio cables. Hence over much of the audio range R dominates over L, and C dominates over G. Only right at the bottom do we have an RG cable, and only around the top (or a bit higher) do we have an LC cable. In the middle we have an RC cable, for which diffusion is a better conceptual model than wave propagation.

Take a sheet of metal. Heat it at one point (or a small area). The heat will flow out to the rest of the metal. When this heat flow reaches the edge does it reflect back to the hot point? No, because there is no wave propagation. Of course, the edge heating up will reduce the heat flow to the edge but this is not reflection. Over much of the audio frequency range this diffusion model is what we should think of when considering a cable; not a wave propagation model.
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So how does this then change into a TL with reflections at RF? frequencies?
 
#20,603
johnego said:
That's opposite of my opinion/finding.
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Sorry to hear. That's the opposite of my observation / finding.
There is misunderstanding here, about the meaning and interpretation of 'accurate' or 'true to the source'. What is your criteria of accurate to the source? I don't do PM or GM analysis. I don't do square wave test etc. The load to the amp is not resistive and accuracy could be subjectively better determined from the final signal that enters the ears. An amp may have 100% similarity between its input and output, but the input may not be accurate (due to source loading) and the speaker output may be way off.
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It's been debated on this thread already. Try the search function. Whatever you read, make sure to go back more than 3 pages.
 
#20,605
Markw4 said:
Yes, of course they can. However, we do not necessarily choose to measure everything that might be audible for at least some listeners. For instance, there are now some dacs that measure quite well, Gustard offering one example. However, their great measuring dac is quickly earning a reputation for sounding worse than some other dacs in the same price range that do not measure as well. It means that designers are starting to get good at designing to a standard regimen of tests, but they still have not learned to listen. Or, it could mean that the standard regimen of dac tests needs to be augmented with additional tests that better correlate with how humans hear.
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For completeness, or those that hear a difference are wrong / fooled by peeking or somesuch.
 
#20,607
Markw4 said:
Yes, of course they can. However, we do not necessarily choose to measure everything that might be audible for at least some listeners. For instance, there are now some dacs that measure quite well, Gustard offering one example. However, their great measuring dac is quickly earning a reputation for sounding worse than some other dacs in the same price range that do not measure as well.
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How did they figure that out? Let me guess, through none level matched and sighted listening.
It means that designers are starting to get good at designing to a standard regimen of tests, but they still have not learned to listen. Or, it could mean that the standard regimen of dac tests needs to be augmented with additional tests that better correlate with how humans hear.
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It doesn't mean squat unless they've done objective listening comparison.
 
#20,608
Debate is not going to solve disagreement about transmission line behavior existence. It is pretty much the same type of thing as the old debates about what is audible vs imagination. What is really being demonstrated is that scientists and engineers are humans before and above anything else.
 
#20,609
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#20,610
jneutron said:
So you instantly recommend parallel connections of zip to lower the inductance and center the HF image.

No fair, we need tests!!!😉

jn
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I would recommend the lowest Ls cable you can find OR locate the PA close to the speaker.
 N.Pass showed such interaction with amps/cables and load causing large FR variations. tests done... Just explaining it.

The only thingy that matters in speaker cable with conventional loudspeaker design is the Ls. Any amount of shunt cable C can be quickly charged with PA's current available. And, so the characteristic Z and everything that follows from it is a non factor to any significant degree.

THx-RNMarsh
 
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#20,616
scottjoplin said:
Yes, but then what interconnect to use? Fancy Interconnects? How about a potato, or even mud?
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With interconnect, it is just the opposite situation. low current capability from OPS (compared to PA) and resistive load. High Z termination/load. So, the series Ls is very small compared to load. The shunt C of the cable is the dominant issue for interconnects (not considering shielding and grounding etc).

Use the lowest cable C as possible.



THx-RNMarsh
 
#20,618
RNMarsh said:
I would recommend the lowest Ls cable you can find OR locate the PA close to the speaker.

N.Pass showed such interaction with amps/cables and load causing large FR variations. tests done... Just explaining it.

The only thingy that matters in speaker cable with conventional loudspeaker design is the Ls. Any amount of shunt cable C can be quickly charged with PA's current available.

And, so the characteristic Z and everything that follows from it is a non factor to any significant degree.
THx-RNMarsh
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Which is exactly what I've been advocating. Lower the RF z, and lower Ls follows with higher capacitance..tomaytoes, tomahtoes..

The only concern with long interconnects is the ground loop possibility. If amp and pre are too far away, I can see people plugging the pre into an outlet a ways away from the amp outlet, or worse yet, on a different branch circuit entirely.
I would prefer using a Power distribution strip for the whole system if current draw allows.

jn
 
#20,619
jneutron said:
The power companies running long transmission lines should call you for advice..
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They use quite thick wires (low R), widely spaced (high L), with very good insulators (low G). Hence it may be that the LC model is still useful for them at 50 or 60Hz.

mmerrill99 said:
So how does this then change into a TL with reflections at RF? frequencies?
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Yes. At higher frequencies L and C dominate so you get wave propagation and hence reflections become possible.

Markw4 said:
Debate is not going to solve disagreement about transmission line behavior existence.
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It seems so. The theory seems clear to me. Experiments, as we have already seen (e.g. CB), can run into trouble when the experimenter applies misunderstanding to what his instruments tell him.
 
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