glassner@cwruecmp.UUCP (Andrew Glassner) (09/19/83)
I am currently in the market for a new casette deck (see a related article in net.audio). As I was writing up the other article I remembered an incident that occurred when I was originally shopping for my system about three years ago. I was travelling on Route 18, which is highway in New Jersey where a whole slew of stereo chains have stores, as well as many local/independent outfits. I was just driving down the road, stopping, looking and listening in these various places, to get an idea of what was around, what features were available, and to get a handle on the state of the art of medium-priced stereo gear. At one point I engaged in a discussion with a salesman (I think this was at Tech HiFi) about the various merits of some of the different decks he was selling. One deck had two heads, another had three, one had mechanical meters, another had LEDs, and so forth. I told him I didn't really care about whether I had mechanical meters or LED, as long as I could detect strong peaks (say with a seperate +5dB light). He put on his "aghast look at the naive stereo buyer-I'll do you a favor because I like you" face and told me that I MUST buy a deck with digital metering. "No," I said, "that's not important to me." "But you HAVE to have digital meters!" he insisted. I wasn't reaching for my checkbook so he went on, and this was his big selling point (as well as the punchline to the story): "You don't understand," he told me. "Music travels in a stereo system as electrical signals, not as musical signals. Electricity travels at the speed of light, which is lots faster than the speed of sound. You need meters which are lights, because only they can respond to the signals inside the stereo which are travelling at the speed of light!" I wonder if we would need faster-than-light meters if I operated the casette deck inside a moving car... -Andrew Andrew Glassner decvax/cwruecmp/glassner
sigurd@uiucuxc.UUCP (09/21/83)
#R:cwruecmp:-66000:uiucuxc:18500007:000:136
uiucuxc!sigurd Sep 20 17:08:00 1983
No ... I think meters that are just as fast as the speed of light should
do the job. (As we all know from the laws of Einstein)jeff@tesla.UUCP (Jeff Frey) (09/22/83)
The dealer`s not SO dumb. Meters have inertia, take time to respond to peaks; in fact, may not get there by the time the signal`s dropped. Therefore, meters can`t give a good indication of real peak levels. Some decks have meters + an LED to indicate whether some peak level has been exceeded. Some LED decks (e.g., my Sony TCFX66) hold the peak LED reading for a second or two so you can see where you`ve been. It`S pretty useful, especially when recording CD`s. Jeff
notes@ucbcad.UUCP (09/25/83)
#R:tesla:-20900:ucbcad:4600001:000:783
ucbcad!max Sep 24 22:15:00 1983
I didn't see the article that prompted this one, but I thought I'd
respond to the statement about meters, as it's a little misleading.
Ordinary analog meters can indeed display true peak values. Meters
have dynamics ("inertia"), as do eyes, limiting their response to rapid
events. This can be largely removed with compensation techniques that
drive the meter with a suitably predistorted signal, so the display
responds much faster; I've seen it done. This is a basic application
of classical control theory. Even simpler, an analog meter can be preceded
with a nonlinear peak-following circuit.
My point: it's untrue that meters "can't" display peaks; often they
don't, but this reflects on the designers of the system, not the display
technology.
Max Hauser (UC Berkeley)