Hit and run posting:
Not unknown physics but perhaps not enough readily known pyschoacoustics?
Hearing isn't linear either with respect to intensity or frequency.
It probably isn't "linear" with respect to discrimination between noise and musical information. Or noise which tracks musical information.
Question: how far down in the noise floor do you have to bury musical signal before it's not noticeable in some fashion, and at what listening levels?
Not unknown physics but perhaps not enough readily known pyschoacoustics?
Hearing isn't linear either with respect to intensity or frequency.
It probably isn't "linear" with respect to discrimination between noise and musical information. Or noise which tracks musical information.
Question: how far down in the noise floor do you have to bury musical signal before it's not noticeable in some fashion, and at what listening levels?
myhrrhleine wrote/asked
For the record. No. And I did not make that claim.
There is however a real and repeatable difference shown by physical measurement. That difference is shown in RF immunity testing (to EN 61000-6-2:2001 and more specifically , to EN 61000-4-3:2002) and PWR-to-GND plane impedance measurements.
For the record. No. And I did not make that claim.
There is however a real and repeatable difference shown by physical measurement. That difference is shown in RF immunity testing (to EN 61000-6-2:2001 and more specifically , to EN 61000-4-3:2002) and PWR-to-GND plane impedance measurements.
QSerraTico_Tico wrote
If you do not want to do the homework, then use the default 100nF ceramic (preferably in an SMT package and NPO/COG dielectric). One on each supply pin and as close to each supply pin as possible.
Is this the best? Will it even work? You won't know unless you simulate/measure/listen (pick your religion) the particular instantiation in front of you.
If simulating; you will need to prepare good second order models. And unless you have a good 3-field solver for the pcb structure then this is still only an approximation
If measuring; then find a network analyser, RF signal generator and wideband scope (1GHz minimum bandwidth on all counts) and do some serious work in a shielded environment.
For both of these you will need to do your homework to get results that are meaningful and then some more homework to interpret the results and actually improve yr circuit performance
If listening, ...
If you do not want to do the homework, then use the default 100nF ceramic (preferably in an SMT package and NPO/COG dielectric). One on each supply pin and as close to each supply pin as possible.
Is this the best? Will it even work? You won't know unless you simulate/measure/listen (pick your religion) the particular instantiation in front of you.
If simulating; you will need to prepare good second order models. And unless you have a good 3-field solver for the pcb structure then this is still only an approximation
If measuring; then find a network analyser, RF signal generator and wideband scope (1GHz minimum bandwidth on all counts) and do some serious work in a shielded environment.
For both of these you will need to do your homework to get results that are meaningful and then some more homework to interpret the results and actually improve yr circuit performance
If listening, ...
Scott, do you know what a Shakti Stone or a 'Brilliant Pebble' device actually is? Have you even tried to find out?
These devices DO something. It can be shown that they do, by lab measurement or listening. Why do you 'condemn without examination' devices that you have little or no knowledge of?
What happens is that we push the 'inventors' of the devices away from the engineers, and they just carry on their own, selling 'results' rather than good explanations.
I have conversed with both inventors of these devices, and have been sent samples of their products. I also have tried to understand the nature of these devices and what they tend to do. Both are high frequency energy absorbers. Is this useless in audio? I think not.
It would be like I built and sold a glue-on heat sink for your IC's, and found it to improve sound quality, then to be condemned for selling VooDoo. Have you tried heat sinking your IC's lately? How about increasing the output quiescent current in your AD797? This is what separates the subtle from the ordinary.
These devices DO something. It can be shown that they do, by lab measurement or listening. Why do you 'condemn without examination' devices that you have little or no knowledge of?
What happens is that we push the 'inventors' of the devices away from the engineers, and they just carry on their own, selling 'results' rather than good explanations.
I have conversed with both inventors of these devices, and have been sent samples of their products. I also have tried to understand the nature of these devices and what they tend to do. Both are high frequency energy absorbers. Is this useless in audio? I think not.
It would be like I built and sold a glue-on heat sink for your IC's, and found it to improve sound quality, then to be condemned for selling VooDoo. Have you tried heat sinking your IC's lately? How about increasing the output quiescent current in your AD797? This is what separates the subtle from the ordinary.
janneman said:
Hi Jan,
This reminds me the classic problem of the negative proof :
http://en.wikipedia.org/wiki/Negative_proof
Regards
If your analog audio circuit isn't oscillating, doesn't burst into oscillation, or isn't near oscillation, the RF characteristics of the circuit including PCBs will have no effect on the sound UNLESS it produces artifacts at lower frequencies that humans can actually hear.
I own a class D amp and the output is completely polluted by RF. On a scope at low levels it looks like RF hash pulsing with the music yet the treble is as clear as a bell. Another case of, "I can measure it but I can't hear it."
I own a class D amp and the output is completely polluted by RF. On a scope at low levels it looks like RF hash pulsing with the music yet the treble is as clear as a bell. Another case of, "I can measure it but I can't hear it."
forr said:
More like Bertrand Russell's famous teapot:
If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is an intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense. If, however, the existence of such a teapot were affirmed in ancient books, taught as the sacred truth every Sunday, and instilled into the minds of children at school, hesitation to believe in its existence would become a mark of eccentricity and entitle the doubter to the attentions of the psychiatrist in an enlightened age or of the Inquisitor in an earlier time.
1audio wrote
Closer spacing does help as the distributed capacitance rises. However to get any real benefit from this you need special pcb layer stackups that have very close inter-plane spacing. 'Normal' (read, cheap) multi-layer pcbs have even spacing of the layers so this benefit is not significant at the 4-6 layer mark.
Shorter vias will reduce inductance but this is only applicable if you use blind or buried vias. These raise the cost of the pcb significantly, unless you have an application where the higher component density means that you can reduce the overall pcb area. IF the pcb area is reduced sufficiently, then the panel yield (number of pcbs per manufactured panel) increases. This means a reduction in per pcb cost which can more than compensate for the cost increase from using HDI techniques.
Not all is lost for simple 6 layer boards however, because you can use a stackup that uses the GND and PWR planes as shield for two internal signal layers. The shielding benefit is more significant than the reduced distributed capacitance that arises from separating the GND/PWR plane pair (c.f. usual 4-layer pcb stackup)
Closer spacing does help as the distributed capacitance rises. However to get any real benefit from this you need special pcb layer stackups that have very close inter-plane spacing. 'Normal' (read, cheap) multi-layer pcbs have even spacing of the layers so this benefit is not significant at the 4-6 layer mark.
Shorter vias will reduce inductance but this is only applicable if you use blind or buried vias. These raise the cost of the pcb significantly, unless you have an application where the higher component density means that you can reduce the overall pcb area. IF the pcb area is reduced sufficiently, then the panel yield (number of pcbs per manufactured panel) increases. This means a reduction in per pcb cost which can more than compensate for the cost increase from using HDI techniques.
Not all is lost for simple 6 layer boards however, because you can use a stackup that uses the GND and PWR planes as shield for two internal signal layers. The shielding benefit is more significant than the reduced distributed capacitance that arises from separating the GND/PWR plane pair (c.f. usual 4-layer pcb stackup)
Hi Demian,
I know this is ancient history here, but I got a few spare minutes and a recently machined block of Delrin and measured no residual charge from the machining process. Tested a few pieces of FR-4, same results, a mental sidetrack that needed to be explored after your mention of a Delrin chassis. Just an FYI.
Best regards, Mike.
fredex said:
I'm curious as to what you base this on? My efforts seem to point to different results and I only work in the audio band (relative to the megahertz and beyond efforts discussed here regularly).
Although I agree with your comments about immunity to external influeces, But once again I feel this characturistic is all based on the layout.
Regards, Mike.
MikeBettinger said:
You're quick, I edited out the last bit, but you agree anyway.
The first statement is just based on logic. There has been much talk of RF and I guess I am just pointing out that we cannot hear RF even if our speakers could produce it. Layout has effects no argument but for normal sized circuits (physical) they are above the frequencies we can hear. All things being equal the audio currents that are responsible for what we hear don't care if they are travelling left, right or up and down on a PCB.
Once, someone modified a Vendetta power supply and made it oscillate at 150MHz or so. They could hear the difference, but they could not measure it, because their scope was not fast enough. This was due to bypass cap selection and layout. This is the sort of thing that we want to avoid, I should think.
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