sjc@mordor.UUCP (Steve Correll) (08/14/84)
I honestly do not know why cables are reported to affect the sound of
audio systems, but I will offer some hypotheses which one might test:
1. Many phonograph cartridges are quite sensitive to load
capacitance. I have seen graphs in Audio magazine suggesting that
cables and preamp inputs vary enough in capacitance to affect the
high-frequency response of a cartridge by several dB, whereas people
seem able to discern variations of less than 1 dB.
Since the optimum value of capacitance varies with the cartridge in
question, simply minimizing capacitance may make some perform better
and others perform worse.
If high-end audio manufacturers were really interested in improving
turntables, they would stop touting pads, platters, and bases made out
of esoteric substances, and they would start putting a few FETs inside
the cartridge itself to isolate its coils from the load of the cables
and preamp. With current technology, the circuitry would increase the
mass of the cartridge/arm combination very little. (In fact, the tiny
additional wire required to bring a few milliamps from a power supply
in the base of the turntable up through the arm to the cartridge would
probably weigh more!)
2. A few preamps are overly sensitive to load capacitance. Studios
insist that line outputs be able to drive low-impedance but reactive
loads without straining, and the IHF/EIA specs define a reactive load
to be used in testing preamps. But one trend in high-end audio is to
minimize both the amount of active circuitry and the amount of feedback
used in amplifiers, and the tradeoff for this is often to make the whole
system more sensitive to loading.
3. Contact corrosion can subtantially affect audio signals whose
amplitude is less than a few dozen millivolts during quiet music.
4. A cable which admits RFI might cause active circuitry to saturate
or slew even though the interference frequencies are too high to hear.
5. Double-blind tests are fairly rare in this field. While I like to
consider myself objective, if I were at a wine-tasting party and I
liked a Gallo wine better than a Chateau St. Jean, I certainly wouldn't
admit it. If you hid the labels, however, there's no telling what
embarrassing judgements you might elicit from me.
--Steve Correll
sjc@s1-c.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjc
--
--Steve Correll
sjc@s1-c.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjcnewton2@ucbtopaz.CC.Berkeley.ARPA (08/18/84)
Boy, I really liked the substance *and* the tone of Steve Correll's posting- a rare combo of sensible analysis and to-the-heart-of-the-matter psychology. I share Steve's interest in double-blind testing of the sometimes passionate assertions of some audiophiles. But I have to admit to a slightly more irasciblebias-- I believe in my bones all this pseudo-scientific mumbo-jumbo is just highfalutin rationalization for onanistic consumer-frenzy. The trend in "high-end" audio is to advance the state-of-the-scam by proposing a new high-tech (preferably MIL-spec) overkill approach to a problem well- characterized by Shannon decades ago, then come up with a post-hoc "discovery" of a problem the gold-plated ether-pipe transmission line supposedly needs to solve. Most of the allegations of shortcomings in conventional approaches to audio seem to share an *intuitive* plausibility and equally to lack an *engineering*, i.e., a quantitative perspective. A good illustration was offered when a net subscriber }inon-confrontationally accepted the assertion that welding cables made an audible difference, but w~rondered what he was losing due to the sub-optimum *internal* wiring of his equipment Sensible people involved with audio on a practical (what hobbyists seem to call "professional") level ought toknow that the signals which golden-eared pundits claim are being raped, pillaged and plundered by connectors that won't pass S-band have seen some shabby indig- nities on their way to the audiophile that one would at least *expect* to rend the shimmering veil from their virginal form (is this sentence over yet?). Anyway. it's sure a good idea to buffer the phono cartridge close to the stylus, but you don't need to pay a mass penalty with an extra wire for power-- easy to share power and signal lines. Interestingly, in the (I just claimed) sane and sober pro world, this obviously optimum approach seems not to catch on withmicrophones, which should be line level from the capsule- would simplify all recording consoles and allow a better approach to digital audio's potential. Nevertheless, people seem to think that Real Mikes Don't Put Out Volts. So any well- designed console today is still limited by the noise figure of its mike preamp *plus* the vagaries of getting the signal to it intact.
wunder@wdl1.UUCP (wunder ) (08/28/84)
I had a friend who accidentally double-blind tested cables on his roommate. He bought some whiz-bang cables for preamp-to-power amp, installed them, them left to do his radio shift. His roommate came home, fired up the stero, and noticed that it sounded better. It is most likely that he noticed this while listening to FM broadcast (KTRU, Houston, to be exact). Note 1. Since my friend bought the cables on an impulse, his roommate did not know that something had been changed in the stereo system. That is, he did not even know that he was part of a test. Note 2. Though the roommate is not a "golden ears", he does go to the Symphony (season tickets), and had worked at the campus radio station for some time. My friend is an official audiophile (and electrical engineer), but was astounded that the cables actually made a big difference. Note 3. The system was pretty good before the cables were added -- Riga turntable with some carefully selected moving coil cartidge, Apt preamp, Apt power amp (or maybe he still had the Hafler then), and I forget what speakers he had. It might have still been Eric's (the roommate's) good old JBL L-100's, but I really don't remember. Note 4. The change might have been caused by the clean connections (no oxide) after the new cables were installed. The cables proabably had not been touched for a few months (2-6), but things rot pretty fast in Houston. Broadcasting on 91.7 MegaHertz, with an effective radiated power of 340 watts ... w underwood