The bulk of my wiring experience is with residential electrical (VAC)
and audio signal cables & speaker cables, with some VDC in amplifiers.
Most of the computer cables I needed I could order, so I wasn't usually
terminating them myself.
With audio, it's pretty straight forward. A number of people figure
they'll save some money and avoid the snake-oil cable sellers and make
their own cables. So they buy the materials that others have found work
well, they'd make some cables, and report they don't sound good. The
sound simply isn't clear. Many don't seem to be able to make a quality
solder joint. When they get their friend who knows how to solder to redo
the connections, and the sound is clear. Others get steered to the
crimping connectors, but use pliers or cheap crimping tools. Again,
despite quality materials, not a clear sound. They're just not a quality
connection. So they can learn to solder properly, and be at risk of the
typical stress failures of soldered connections, or the more robust and
much easier to learn path, buy a proper quality crimping tool and learn
to use it. Great connection and repeatable.
Then there's the soldered crimp. It's astounding the number of times
such a connection fails and the wire: moves back and forth, turns in
place or pulls out. The heat from soldering expands the crimp, lowering
its crimping pressure, for a poor crimp connection, but it's still tight
enough while heated that the solder can't wick in. You end up with the
combination of a poor crimp connection and a poor solder connection. I'd
guess that with a poor enough crimping, there could be enough space to
wick solder in...
An engineer told me what was up, and I cut open some connections that
seemed solid to check. In each case there was a gob of solder at the
end, but only some trace solder within the first part of the strands,
with minimal contact between the wire and the crimp. I've cut one open a
number of times over the years since, to show such to people. (Note:
NASA will not accept crimped connections of tinned stranded or tinned
solid wire. I've no idea why, but I figure it's a given that they know a
lot more about terminations and connections than I ever will.)
So my first-hand personal experience is that I've seen dozens upon
dozens of examples over four+ decades where an audio cable terminated
with soldered crimps that did not sound clear, but replacing the
terminations with properly soldered or properly crimped connections and
the sound was then clear. Not a subtle difference, but at minimum a
strong improvement, and usually a night and day difference. Now for
quality consistency, I only use crimps for audio connections and choose
connectors accordingly.
I've heard a lot of speculation over the years as to why this difference
in clarity, but nothing that seems completely credible. The closest to
credible speculation I've heard is:
- a poor connection results in multiple signal paths resulting in a
sightly overlapped signal so the signal is no longer clear, or
- a poor connection has multiple connections and combined with eddy
currents in the connector you can get tiny RC paths instead of a single
long connection, so you've got multiple re-injections of a delayed
signal that smooths tiny changes in voltage, which is your signal.
Causation is clear. The explanation? No idea.
I've heard people say that all this analogue cable stuff doesn't matter
for digital signals because it's digital. Except that if one reads the
specs, the "digital" signal is really an digitally encoded analogue
signal. Back in the main-frame era, a number of times I was able to
correct throughput degradation or outright failure by addressing cable
issues (poor connections, shielding grounding, co-located cables of
identical length so they're sometimes surprisingly effective as
sending/receiving antennas, etc.) that techs thought would only apply in
analogue signals.
So where someone is transferring a timing signal down a cable, depending
on the frequency a quality termination/connection may be important, not
only to the longevity of the cable, but to the quality of the signal,
hence the ease, speed or consistency with which it drives and triggers
what is reading it.
And for power connections, you don't want to hope you detect the signs
of a failing loose connection due to heat, arc smells, etc. (like the
mushroom-cap screw heads on terminations for containment & detection),
before it outright fails, nor a conductor that comes free if the
wire-to-solder connection breaks. The welded connection is new to me,
but sounds like it could befit in some applications. If you've enough
power and the connection is not tight, I have seem some conductors weld
themselves to a terminal, often with a thin connection; but usually it's
material gets blown away and the conductor is now loose. Lithium battery
packs can deliver some surprising current.
So again, I don't think doing a proper (or poor) crimp connection, then
expanding it with heat to try and wick some solder into gaps that would
have been reduced by crimping and then with heating, is a very good way
to go, along with taking on the risk of the stress failures of soldered
wires.
On 05/10/2019 2:10 PM, Wes wrote:
On 10/4/2019 12:17 PM, MLewis wrote:
With audio signals, a soldered crimp is one of the worst possible
connections.
Please explain.
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