mat@hou5e.UUCP (07/03/83)
``And the illusion is far from perfect, there is room for improvment in the technology. AND UNTIL THAT'S TRUE, QUIT TELLING ME THAT IT'S BETTER THAN I CAN HEAR, BECAUSE IT'S NOT!!'' Hear, hear! True, if an amplifier has .0003 % distortion of sine waves or 2 mixed sine waves it probably is good enough at doing that. But before I bought my preamp, I listened to several ... ALL top-notch, high-endy units. I had the benefit of a patient salesman who had a VERY good pair of speakers on hand, as well as a very good turntable/ tonearm/cartridge and power amp. Very good means considerably better than I own right now, but maybe not much better than I will have six or seven years from now. None of these expensive preamps sounded the same ... none was clearly ``better'' in the basic preamp functions. One had slightly better imaging, one has slightly better response on huge (test-and-demo record) transients. Why? Every year I hear new speakers that sound better than I ever thought possible ... or better than I thought possible at the price. Per dollar, speakers today are far better than they have ever been. Yet the continuing improvement suggests that they are nowhere good enough. I heard a pair of Rogers speakers demo'd with two different cartridges -- one a good brand, and the other a ``carriage trade'' brand. The imaging of these speakers with the first cartridge was spectacular. With the second it was no better than I get with my low-end Yamaha turntable through a set of $150-the-pair Boston A40's. Yes, there is a LONG way to go. And the best gains can always be made by finding and fixing/repacling the weakest link. BTW, anyone have recommendations on tuners or equalizers? I am especially interested in (as I have said before) the new NAD and Carver tuners, since they have enhanced capabilities for dealing with poor signals. hou5e!mat Mark Terribile Duke of deNet (sigh)
gregr@tekig1.UUCP (07/07/83)
You asked why various high end preamps sound different when auditioning them with a phono cartridge at an audio solon...? The answer to this question has been explained very well over the years in audio publications (Audio, others). The major difference is in the way the preamp loads the cartridge. Preamps have widely varying input capacitances which moving magnet cartridges are very sensitive to. (Other complex loading problems also exist and RIAA equalization errors are possible but these are second order effects in well designed and usually expensive preamps.) It is ABSOLUTELY necessary to adjust the input C for each preamp tested to be the same as all others being tested. Since most preamps allow no adjustment or only very coarse adjustments (100 pf steps or so) this must be done with add-on capacitors either internally (best) or externally (rather poor). Different cartridges have different sensitivities to C variations. (I suspect this explains the tendency for subjective reviewers to proclaim that one cartridge is better than another because it allows differences between preamps to be heard. In fact there probably is no correlation between C sensitivity and sound quality.) Notice that we are comparing preamps here and adjusting for equal C for each preamp with ONE cartridge. If the object is to compare cartridges we should use ONE preamp but adjust it for different C values for each cartridge tested. Again this is ABSOLUTELY necessary because each cartridge produces its optimal performance with a particular capacitive load. (This easily explains why certain cartridge-preamp combinations sound better than others.) Also note another related problem due to capacitance. If tonearms (or integrated tonearm-turntable combinations) are to be compared they will have widely varying cable capacitances depending on length and cable type. Therefore to compare tonearms the capacitances must be made equal, but to compare cartridge-tonearm combinations the C values should be optimized for the particular cartridge used. If you think this sounds like a lot of effort to compare differences in the way components sound --- your right! Accurate comparisons between components is virtually impossible in a store regardless of how friendly the salesman is. Notice that I'm not even talking about scientific testing i.e. double-blind controlled statistical testing. Even if you are a "golden eared audiophile with perfect sensory memory and nothing to prove" you still can't make valid tests when you overlook (re don't understand) how components work and their sensitivities. Oh yes, do cartridges and speakers sound differently? Of course, they are electromechanical with widely varying designs and measureable performance differences. Do preamps sound differently? After very time consuming, controlled testing I believe so. But very subtle differencs when testing problems like above are corrected. The problems, defects, and variations of the electromechanical elements will mask virtually all of these differences when the preamp setup is correct. Equalizers however are a completely different story .....
kimr@tektronix.UUCP (07/07/83)
The ear, unlike some quasi-techno-freak audio equipment, was not designed to
receive (produce) only sine waves. Current information is that the ear is
sensitive to signal RISE times on the order of 10 microseconds. Instead of
worrying about sine wave response of the ear, think about a 1000 hertz square
wave with a 10 us rise time. It has sine wave harmonics exceeding 20 khz, and
I'll bet that a well designed experiment will show audible differences if the
rise time is limited to (say) 20 us.
Interestingly enough, the chief difference between moving magnet and moving coil
cartridges is their rise times - on the order of 10us for moving coil and 20us
for moving magnet (16us for the Shure V15-V). A Time-Life book on music, circa
1965, shows the waveform of a kettle drum attack. The caption indicates that
the rise time of the waveform is 12us.
For reproduction, I use KEF T-27 tweeters that are rated -3db at 37Khz.
The Pyramid T-1 ribbon tweeter is -3db at better than 80 Khz. Better yet,
the Pyramid Met-7 ($295/pair) has a PUBLISHED rise time of 10us. I could
continue: Quad ESL -3db @ 35 Khz...
A competent stereo, (with competent source material) can produce an acoustic
illusion which is 3-dimensional - realistic depth front-to-back, extending
beyond the speakers to the sides, and most interestingly, top to bottom
placement of instruments. You should be able to tell where the performers
are in relation to the walls of the space they're performing in. And, if
all goes right, you can convince yourself that you're attending a live
performance, not listening to a mechanical reproduction.
Until your system can reproduce this kind of illusion, it is far from the
state of the art. And until the illusion is perfect, there is room for
inprovement in the technology. AND UNTIL THAT'S TRUE, QUIT TELLING ME THAT
IT'S BETTER THAN I CAN HEAR, BECAUSE IT'S NOT!!
Kim Rochat
..!tektronix!kimr larson@sri-unix.UUCP (07/08/83)
#R:tektroni:-121100:sri-unix:15900003:000:359
sri-unix!larson Jul 5 23:37:00 1983
A kettledrum rise time of 12 microseconds?! Wow. If the head
is deflected .1 inches at initial impact, the mallet will have been
traveling approximately 1388 feet/second, approximately 1.25 times
the speed of sound.
If the deflection is .01 inches, the velocity will still be 139
feet/second, or 95 miles/hour.
hmmm...
Alan Larson
sri-unix!larson