[time-nuts] DC distribution

[Bill Beam]

On Sat, 5 Oct 2019 18:03:33 -0400, MLewis wrote:


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>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.

The engineer failed to explain why this is an electrical problem.

 (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.)


I know why....  They don't like diodes/rectifiers in connections.
Crimped connections can produce point contact junctions thru the
tinning layer resulting in rectification.

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>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

To create a multipath error of 1 electrical degree at 20KHz (inaudible) requires a path
error of about 30m.  Not going to happen in a cm connector.

>- a poor connection has multiple connections and combined with eddy

No eddy currents

>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.

For R<~1ohm, C<~1pF the time constant is <~10e-12sec.  Not in the audio domain.

>Causation is clear. 

Not clear!

>The explanation? No idea.


The explination:  A poor connection rectifies.  For 1% difference between forward
and reverse conduction expect to hear about 1% THD.  To make matters worse the 
rectification will likely be nonlinear with current thru the connection further increasing THD.

Snip

Regards


Bill Beam
NL7F