[ProAudio] Western Electric 111C transformers
jim at audiosystemsgroup.com
Wed Feb 2 11:09:43 PST 2022
On 2/2/2022 6:32 AM, Scott Dorsey via ProAudio wrote:
> It wasn't as bad as you'd think since the frequency-dependent loss of the
> lines was minimum phase and so would be corrected by a minimum-phase
> equalizer that flattened the frequency response.
What is not generally realized is that there are extreme variations in
VF (velocity of propagation) and Zo (characteristic impedance) through
the audio spectrum. They are characteristic of ANY transmission line,
predicted by the full form of the wave equation. As part of research
I've been doing for some ham radio applications, I've done sweep
measurements of more than a half-dozen cables, both coax and
close-spaced 2-wire line, and all clearly show the variations. My
instrumentation is a Vector Network Analyzer.
from the earliest days of telephony, equalization applied to long lines
was as least as important to correct for variations in VF as it was for
amplitude rolloff. I adapted and expanded on a paper by James Hayward, a
retired engineer from Canadian telco who I met through Neil Muncy. I
wrote this in 2005 to debunk some of the mythology that had been
circulating at the time.
More information about the ProAudio