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#1
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terminating audio lines like RF
http://www.borbelyaudio.com/kit_upgrades_term.asp
Is this total hooey, or what? I thought at audio frequencies these effects are very small, and completely imperceptible. The longest mic cable I ever use is 100 ft. But no mic will happily drive 150 ohms. For line levels, the lower Z that any output stage must drive with this approach definitely has distortion and voltage swing drawbacks, versus the 10k input Z of a bridging input. What do y'all think? Dufus |
#2
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Despite my being an audiophile that hears differences between cables, capacitors, and various
other aspects of neurotic audio tweakdom, this particular one is s load of dingo's kidneys. Aside from your correct point that reflection effects in cables are either totally insignificant or non-existent below radio frequencies, there aren't many preamps that would be happy driving the low Z loads this guy is talking about. A handful of preamps, such as tube hybrid preamps with high current mosfet source followers, might sound better into such a low Z load, but merely by virtue of pushing the preamp's output stage into higher current operation for a given volume level, where the performance might be more linear. Perhaps this guy has heard such an effect & has drawn the wrong conclusion about the cause. -- Stephen Sank, Owner & Ribbon Mic Restorer Talking Dog Transducer Company http://stephensank.com 5517 Carmelita Drive N.E. Albuquerque, New Mexico [87111] 505-332-0336 Auth. Nakamichi & McIntosh servicer Payments preferred through Paypal.com "dufus" wrote in message om... http://www.borbelyaudio.com/kit_upgrades_term.asp Is this total hooey, or what? I thought at audio frequencies these effects are very small, and completely imperceptible. The longest mic cable I ever use is 100 ft. But no mic will happily drive 150 ohms. For line levels, the lower Z that any output stage must drive with this approach definitely has distortion and voltage swing drawbacks, versus the 10k input Z of a bridging input. What do y'all think? Dufus |
#3
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Despite my being an audiophile that hears differences between cables, capacitors, and various
other aspects of neurotic audio tweakdom, this particular one is s load of dingo's kidneys. Aside from your correct point that reflection effects in cables are either totally insignificant or non-existent below radio frequencies, there aren't many preamps that would be happy driving the low Z loads this guy is talking about. A handful of preamps, such as tube hybrid preamps with high current mosfet source followers, might sound better into such a low Z load, but merely by virtue of pushing the preamp's output stage into higher current operation for a given volume level, where the performance might be more linear. Perhaps this guy has heard such an effect & has drawn the wrong conclusion about the cause. -- Stephen Sank, Owner & Ribbon Mic Restorer Talking Dog Transducer Company http://stephensank.com 5517 Carmelita Drive N.E. Albuquerque, New Mexico [87111] 505-332-0336 Auth. Nakamichi & McIntosh servicer Payments preferred through Paypal.com "dufus" wrote in message om... http://www.borbelyaudio.com/kit_upgrades_term.asp Is this total hooey, or what? I thought at audio frequencies these effects are very small, and completely imperceptible. The longest mic cable I ever use is 100 ft. But no mic will happily drive 150 ohms. For line levels, the lower Z that any output stage must drive with this approach definitely has distortion and voltage swing drawbacks, versus the 10k input Z of a bridging input. What do y'all think? Dufus |
#4
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"dufus" wrote in message
om http://www.borbelyaudio.com/kit_upgrades_term.asp Is this total hooey, or what? Total hooey. I presume that Borbley didn't get the standard EE lecture about transmission lines that starts out by saying that a cable has to be some fraction (usually at least 1/8 probably far more) of a wavelength at the highest frequency of interest, to be thought of as a transmission line. That's a little more than a mile at 20 KHz. If we lift our sights to SACD-like 100 KHz, we're still talking over 1,000 feet before a cable could in our wildest imaginings be thought of as a transmission line. I thought at audio frequencies these effects are very small, and completely imperceptible. This would be orthodox thinking. However, in a sighted evaluation I might be cable to convince you that you were hearing something. The longest mic cable I ever use is 100 ft. My longest snake is 150 feet and I regularly plug 20-50 feet of mic cable into it. That's a room that is about 80 feet deep. In a big room this could double. But no mic will happily drive 150 ohms. Depends what you call happy. For line levels, the lower Z that any output stage must drive with this approach definitely has distortion and voltage swing drawbacks, versus the 10k input Z of a bridging input. There are some pretty robust line drive output stages out there. Many will drive their building-out resistors (i.e., an external short circuit) to +4 without clipping. They wont' do +22 cleanly, of course. Nonlinear distortion will rise but still remain way below 0.05%. What do y'all think? Borbly has spent too much time reading the pseudoscience in some of the ragazines that publish his construction projects. He seems to believe everything they say. |
#5
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"dufus" wrote in message
om http://www.borbelyaudio.com/kit_upgrades_term.asp Is this total hooey, or what? Total hooey. I presume that Borbley didn't get the standard EE lecture about transmission lines that starts out by saying that a cable has to be some fraction (usually at least 1/8 probably far more) of a wavelength at the highest frequency of interest, to be thought of as a transmission line. That's a little more than a mile at 20 KHz. If we lift our sights to SACD-like 100 KHz, we're still talking over 1,000 feet before a cable could in our wildest imaginings be thought of as a transmission line. I thought at audio frequencies these effects are very small, and completely imperceptible. This would be orthodox thinking. However, in a sighted evaluation I might be cable to convince you that you were hearing something. The longest mic cable I ever use is 100 ft. My longest snake is 150 feet and I regularly plug 20-50 feet of mic cable into it. That's a room that is about 80 feet deep. In a big room this could double. But no mic will happily drive 150 ohms. Depends what you call happy. For line levels, the lower Z that any output stage must drive with this approach definitely has distortion and voltage swing drawbacks, versus the 10k input Z of a bridging input. There are some pretty robust line drive output stages out there. Many will drive their building-out resistors (i.e., an external short circuit) to +4 without clipping. They wont' do +22 cleanly, of course. Nonlinear distortion will rise but still remain way below 0.05%. What do y'all think? Borbly has spent too much time reading the pseudoscience in some of the ragazines that publish his construction projects. He seems to believe everything they say. |
#6
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#7
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#8
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"Mike Rivers" wrote ...
seanbroderick writes: Is this total hooey, or what? Yup. Someone has a good imagination. Boberly had some good construction articles in the early days of The Audio Amateur magazine. Kinda strange to see such wacko stuff out of him how. |
#9
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"Mike Rivers" wrote ...
seanbroderick writes: Is this total hooey, or what? Yup. Someone has a good imagination. Boberly had some good construction articles in the early days of The Audio Amateur magazine. Kinda strange to see such wacko stuff out of him how. |
#11
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#12
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On Sat, 20 Nov 2004 13:02:00 -0500, "Arny Krueger"
wrote: http://www.borbelyaudio.com/kit_upgrades_term.asp Is this total hooey, or what? Total hooey. Are Borbely's resistor values correct for the balanced line? Chris Hornbeck |
#13
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On Sat, 20 Nov 2004 13:02:00 -0500, "Arny Krueger"
wrote: http://www.borbelyaudio.com/kit_upgrades_term.asp Is this total hooey, or what? Total hooey. Are Borbely's resistor values correct for the balanced line? Chris Hornbeck |
#14
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"Chris Hornbeck" wrote in message ... On Sat, 20 Nov 2004 13:02:00 -0500, "Arny Krueger" wrote: http://www.borbelyaudio.com/kit_upgrades_term.asp Is this total hooey, or what? Total hooey. Are Borbely's resistor values correct for the balanced line? Depends on the characteristic impedance of the balanced line? |
#15
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"Chris Hornbeck" wrote in message ... On Sat, 20 Nov 2004 13:02:00 -0500, "Arny Krueger" wrote: http://www.borbelyaudio.com/kit_upgrades_term.asp Is this total hooey, or what? Total hooey. Are Borbely's resistor values correct for the balanced line? Depends on the characteristic impedance of the balanced line? |
#16
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"Richard Crowley" wrote in message
"Mike Rivers" wrote ... seanbroderick writes: Is this total hooey, or what? Yup. Someone has a good imagination. Boberly had some good construction articles in the early days of The Audio Amateur magazine. Kinda strange to see such wacko stuff out of him how. TAA has a long history of flirting with pseudo-science. |
#17
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"Richard Crowley" wrote in message
"Mike Rivers" wrote ... seanbroderick writes: Is this total hooey, or what? Yup. Someone has a good imagination. Boberly had some good construction articles in the early days of The Audio Amateur magazine. Kinda strange to see such wacko stuff out of him how. TAA has a long history of flirting with pseudo-science. |
#18
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On Sat, 20 Nov 2004 16:04:57 -0800, "Richard Crowley"
wrote: Are Borbely's resistor values correct for the balanced line? Depends on the characteristic impedance of the balanced line? He specifies "110 ohm" cable and 110 ohm build-out and load resistors. I guess my question goes to the cable's spec method. Chris Hornbeck |
#19
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On Sat, 20 Nov 2004 16:04:57 -0800, "Richard Crowley"
wrote: Are Borbely's resistor values correct for the balanced line? Depends on the characteristic impedance of the balanced line? He specifies "110 ohm" cable and 110 ohm build-out and load resistors. I guess my question goes to the cable's spec method. Chris Hornbeck |
#20
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Is this total hooey, or what? I thought at audio frequencies these effects are very small, and completely imperceptible. The longest mic cable I ever use is 100 ft. But no mic will happily drive 150 ohms. For line levels, the lower Z that any output stage must drive with this approach definitely has distortion and voltage swing drawbacks, versus the 10k input Z of a bridging input. What do y'all think? Dufus It's bunk. For the example they gave, the driving side of the cable was terminated. THe reflection would bounce back from the load and be absorbed back into the pre-amp source Z. The load side would still have a perfect signal even if it were an RF signal. There is only a problem if the signal is re-reflected back toward the load. At audio wavelengths, the cable would have to be very long to create a problem. What can be a problem, if the source cannot drive the capactiance of a mismatched cable, the high end may be rolled off. Mark |
#21
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Is this total hooey, or what? I thought at audio frequencies these effects are very small, and completely imperceptible. The longest mic cable I ever use is 100 ft. But no mic will happily drive 150 ohms. For line levels, the lower Z that any output stage must drive with this approach definitely has distortion and voltage swing drawbacks, versus the 10k input Z of a bridging input. What do y'all think? Dufus It's bunk. For the example they gave, the driving side of the cable was terminated. THe reflection would bounce back from the load and be absorbed back into the pre-amp source Z. The load side would still have a perfect signal even if it were an RF signal. There is only a problem if the signal is re-reflected back toward the load. At audio wavelengths, the cable would have to be very long to create a problem. What can be a problem, if the source cannot drive the capactiance of a mismatched cable, the high end may be rolled off. Mark |
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