That's SOP we had a bell jar in the MEM's mic lab. Interesting IIRC the Sennheiser's typically are specified pretty close to the limit for the capsule diameter as stock items.
He he.
In a few words, we have the answer all right but what is the question?
"Slartibartfast, a planetary coastline designer who was responsible for the fjords of Norway, relates the story of a race of hyper-intelligent pan-dimensional beings who built a computer named Deep Thought to calculate the Answer to the Ultimate Question of Life, the Universe, and Everything. When the answer was revealed to be 42, Deep Thought explained that the answer was incomprehensible because the beings didn't know what they were asking. It went on to predict that another computer, more powerful than itself would be made and designed by it to calculate the question for the answer. (Later on, referencing this, Adams would create the 42 Puzzle, a puzzle which could be approached in multiple ways, all yielding the answer 42.)"
Audio Lab | Microsoft: Inside B87
George
Looking up intrinsic capacitance values in datasheets one often sees the 1MHz stated, I guess that's the frequency most manuf. tests their semis with, and some Vds value, often 10 or 25V.
Found some drawings in an old NS databook, maybe these circuits may help to design a capacitance measurement jig.
some links:
http://pessina.mib.infn.it/Biblio/Biblio_Articoli/NIMA V A469 p 116 126 2001.pdf
https://www.maximintegrated.com/en/app-notes/index.mvp/id/5086
Found some drawings in an old NS databook, maybe these circuits may help to design a capacitance measurement jig.
some links:
http://pessina.mib.infn.it/Biblio/Biblio_Articoli/NIMA V A469 p 116 126 2001.pdf
https://www.maximintegrated.com/en/app-notes/index.mvp/id/5086
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Hi, nantech,
My speaker's lines are shielded.
Some consider that one of the benefits of switching PSUs is the improved isolation with the AC lines.
Hi Tryphon,
Using shielded cable for speaker cable can sometimes provoke an amplifier into oscillation. It will see that distributed capacitance for sure. You may very well be better served by an LC network right at the output terminals. That way the parallel capacitance is isolated by the inductance of the filter network.
I do use a lot of shielded speaker cable in paging systems But those amplifiers are typically using a transformer for the 70 V line to the speakers. That capacitance (over hundreds of meters!) doesn't seem to affect the amplifiers. Of course, the speaker is driven from the transformer which doesn't need a ground reference, so capacitance to ground would cause a lot less for the amp to deal with.
-Chris
Using shielded cable for speaker cable can sometimes provoke an amplifier into oscillation. It will see that distributed capacitance for sure. You may very well be better served by an LC network right at the output terminals. That way the parallel capacitance is isolated by the inductance of the filter network.
I do use a lot of shielded speaker cable in paging systems But those amplifiers are typically using a transformer for the 70 V line to the speakers. That capacitance (over hundreds of meters!) doesn't seem to affect the amplifiers. Of course, the speaker is driven from the transformer which doesn't need a ground reference, so capacitance to ground would cause a lot less for the amp to deal with.
-Chris
Very few properly designed amplifiers will exhibit problems with shielded speaker cable. The worst offenders are Naim amplifiers, though there are others. Almost any amp with low or zero global NFB will not have any problems. Valve amps will generally be fine.
FWIW: I have, for many years, promoted RG213/U is a very inexpensive, very high performance speaker cable. It has commendably low resistance, low inductance and is very cheap. Additionally, it is an excellent choice for those living in an environment with high levels of RF interference.
FWIW: I have, for many years, promoted RG213/U is a very inexpensive, very high performance speaker cable. It has commendably low resistance, low inductance and is very cheap. Additionally, it is an excellent choice for those living in an environment with high levels of RF interference.
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Hi Zaphod,
-Chris
While I would agree with you, a few nF of capacitance should not cause problems, I have seen a number of amplifiers over the years that simply wouldn't put up with that amount. Just trying to err on the safe side, and a proper LC filter can be more effective at blocking RFI. That, and shielded cables tend to be stiffer and larger than straightforward wire. I'm talking about 18/2 or 16/2 in a shield, twisted pair. If you are talking about using straight coax ... well I can't get on board for that at all.
-Chris
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