Home Computer Audio Asylum

Music servers and other computer based digital audio technologies.

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Computer Audio Asylum ]
[ Alert Moderator ]

a bit of ancient digital history...

"The computer audio was intentionally designed this way not to give CPU the last word in data transfer. The engineers would have had to be completely dumb to allow that."

Back in the 1960's when transistors were very expensive and data rates were very slow some engineers designed a multiline teletype interface for a minicomputer to work just like you suggest. This worked OK until a salesman tried to sell it to a PTT (Post, Telgraph and Telephone) authority down under. (AU or NZ, I don't recall which.) It turns out that they required all equipment to meet a tight jitter specification. (Tight because it required jitter in the microsecond region for telegraph lines running at 50 bits per second or slower.) As it turns out the software could not meet this number when it was handling a large number of lines and the product was too expensive if the computer was restricted to a small number of lines. So, you could say the engineers were dumb. But I knew them and they weren't completely dumb. They designed a new version that provided a bit buffer and solved the jitter problem.

One might wonder why a 50 bit per second telegraph interface needs jitter in the microsecond region. It has to do with telegraph distortion which starts at the transmitter, goes through the wires (large L, C and R) and ends up at the receiver which has to sort out the mess. Tight specifications reduced the chance a marginal telegraph line might garble the signal. (The lines would blow around in the wind and the dialectric would vary according to the weather, hence inconsistent distortion.)

Not much has really changed in over 40 years. Transistors cost much less, and time is now measured in units of picoseconds instead of microseconds. Bits weren't just bits back then and they aren't just bits today. (Time resolution in the analog domain is much smaller than time resolution in the digital domain according to the signal to noise ratio.)

BTW, telegraph distortion was very old hat in the 1960's.



Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar

This post is made possible by the generous support of people like you and our sponsors:
  Amplified Parts  

Follow Ups Full Thread
Follow Ups
FAQ

Post a Message!

 Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]