naturerecordists
[Top] [All Lists]

Re: single-point stereo mic

Subject: Re: single-point stereo mic
From: "Walter Knapp" waltknapp
Date: Tue Jun 13, 2006 9:51 am (PDT)
Posted by: ""

>  IIRC, the issue with the 3.5mm / 1/8 inch plugs ("mini plugs") is not so=
 much one of shaft diameter compatibility, but of the size and shape of the=
 tip.

This is a separate issue independent of the shaft diameter, well sort of
independent.

  When Sony introduced the stereo mini plug, it decided to change the
shape of the tip from the more rounded style of the old mono 1/8" to a
more trapezoidal shape. Some other manufacturers followed suit, others
did not. So there are multiple standards within the "mini plug" world.
And if you use a rounded style plug in a jack meant for the trapezoidal
plug, the jack's contacts will bend/fatigue enough so that when you
later try to use trapezoidal plugs in that jack you'll have a higher
incidence of intermittent contact.

Note there are also stereo mini plugs that have the standard rounded
tip. Again I saw those before I ran into the Sony plugs. There are also
variations in shaft length to consider. It's a mess of different sizes
and designs.

I've already commented on the poor quality of springs in jacks. Which is
what you are describing. And is certainly a contributing factor.

Look at it this way, you have a metal shaft in a metal hole. Out at the
end of the shaft is a spring pressing lightly on one side of the shaft.
This pressure causes the shaft to tilt as it goes through the hole until
it makes contact with the metal of the hole (one of your contacts). The
pressure of the spring on the tip provides it's contact. If the shaft is
a close fit, then the tilt is not much and the spring is loaded more
making for greater contact pressure both in the hole and at the spring.
This greater pressure helps to make contact even if things are a little
dirty, the system is designed with a wiping action to be somewhat self
cleaning. Now think about a loose fitting shaft, the tilt in the hole is
much greater, and the longer length out to the spring contact means that
the distance of movement is magnified, up to a mm or more at the spring.
The spring will not have near as high a contact pressure, the contact
pressure in the hole will be less too. Much more vulnerable to small
amounts of dirt or corrosion or small vibrations. The size of the shaft
does matter, it all matters.

As I noted, when you have problems with these mini plug systems it's
worthwhile checking just how loose that plug is in the hole. If it seems
loose it's worth checking the plug diameter and hole diameter for a
mismatch. Or you can fiddle frequently with cleaning a self cleaning
system, tape or whatever for temporary fixes. Your choice. Has anyone
measured the plug and jack in question?

As for the tip shape being the problem, that's one channel. The other
channel hot is on the intermediate sleeve. So the problem of tip shape
will manifest itself consistently in only one channel. Single channel
problems are often damaged or weak spring contacts. Usually the only
permanent fix is a new jack.

All of which makes me very happy I don't use the system except for
headphones. And I use top quality XLR in my mic cables too. Though I
don't consider XLR to be a perfect design either.

Walt





<Prev in Thread] Current Thread [Next in Thread>
Admin

The University of NSW School of Computer and Engineering takes no responsibility for the contents of this archive. It is purely a compilation of material sent by many people to the naturerecordists mailing list. It has not been checked for accuracy nor its content verified in any way. If you wish to get material removed from the archive or have other queries about the archive e-mail Andrew Taylor at this address: andrewt@cse.unsw.EDU.AU