[sdiy] "Mini-jack" myths

[Graham Atkins]

As you mention, 1/4" jacks have their origins in telephony dating back  
to
probably early 20th century (If not before). I stand to be corrected  
but I believe
the 2.5mm and 3.5mm jacks have their origins in Japanese transistor  
radios
used for earpieces or "record out" connections. This is where I first  
encountered
them. I think the Switchcraft Bantam TT plugs are an odd one unique to  
them.

Graham

On 25 Jan 2010, at 22:34, flightofharmony wrote:

> This is one of those subjects that is plagued by misconceptions and  
> urban
> legends which just won't die - and it keeps coming up. I did a lot of
> research into this when I started building, and here's the details I
> discovered. But first, I want to make it clear that this is based on  
> that
> research, which is still ongoing, and that nobody can ever know  
> everything
> about anything, so I welcome any additional information or  
> corrections - as
> long as they are politely-worded and include actual details and not  
> just
> hearsay. In addition, I do not cover (or care, just yet) any new  
> variations
> on this theme, as most are platform-specific and yet available to the
> general public.
>
> While there is a large body of misinformation in audio electronics,  
> this is
> one area where blindly following the common opinion can actually cause
> physical damage to your equipment, so we'll start with:
>
> There is no such thing as a 1/8" telephone (also called "phone")  
> jack or
> plug - at all, ever.
> I blame Switchcraft for propagating this myth. As far as I have been  
> able to
> find, they chose uncommon fractional sizes for their smaller jacks  
> (9/64"
> and 3/32") which use too many syllables when spoken and were not
> commonly-available characters in typesets for the printing presses  
> of the
> time, so they rounded to the nearest common designators (1/8" and  
> 1/16").
>
> 9/64" = 0.1406" = 3.572mm
> 1/8" = 0.1250" = 3.175mm
> 3.5mm = 0.1378"
>
> 7/64" = 0.1094" = 2.778mm
> 1/16" = 0.0625" = 1.588mm
> 2.5mm = 0.0984"
>
> Switchcraft sizes:
> "Tini" = 0.141" = 3.581mm
> "Micro" = 0.097" = 2.464mm
>
> "Mini-jack" is the term often used to cover a large range of different
> jacks, namely: "Tini", 3.5mm, 2.5mm, and "Micro". The only  
> consistent aspect
> of these jacks is that they are all smaller than the old 1/4"  
> standard jack
> used originally for cross-patching telephone circuits. "Micro-jack" is
> sometimes used to describe the two smaller formats -  2.5mm and  
> 0.097". For
> the rest of this I will focus on the 3.5mm and 0.141" sizes.
>
> These sizes are *not* mutually interchangeable.
>
> A 0.141" plug in a 3.5mm jack will often damage the leaf contacts in  
> the
> jack, shortening the life. Sometimes the jack will be ruined for 3.5mm
> plugs.
> A 3.5mm plug in a 0.141" jack will often work, but that depends upon  
> which
> 0.141" jack. The plug will sit a little loose but still make  
> contact, but
> switched jacks usually do not switch - particularly the Switchcraft  
> 142.
>
> Switchcraft:
> They make excellent jacks and plugs, don't misunderstand that, but  
> they are
> very American in their approach to metric sizes (and change in  
> general). The
> only 3.5mm jacks that they *manufacture* are the 35PM1 and 35PM2.  
> All the
> other jacks *offered* by them are manufactured overseas. In fact,  
> they are
> standard offerings from a large number of Asian companies.
> The only 3.5mm plugs that they *manufacture* are the 35HD series.  
> They are
> very nice plugs! But they are only available in stereo configuration.
> I had a meeting with the Switchcraft Northwest regional manager to  
> discuss
> custom jack designs, which is where I learned a lot of this. Also  
> that they
> have no interest or inclination to pursue any metric products.
>
> Plug geometries:
> This is the shape of the plug when viewed from the side. The initial  
> angle
> of the tip, the distance of the first "lip" from the tip, and the  
> angle and
> curvature of the notch.
> There are several different geometries floating around, but very  
> little
> information that I could find. Some jacks are intended for a  
> particular plug
> geometry, while some are apparently "one size fits all" with accordant
> results.
> Mis-matching plug and jack geometries can have various effects:
> Plug seats early or late
> Plug does not seat perpendicular to jack
> Bad or intermittent connection
> Plug retention feels loose or "about to pop out"
>
> The most common style seems to be what has been termed the  
> "japanese" style:
> a steep (~45°), flat rise from tip to ridge, sharp angle at the  
> ridge, a
> shallow (~15°) slope to the notch, and a sharp angle at the notch.  
> Most
> european jacks are intended for these. The other styles may have:
> rounded top to the ridge
> rounded bottom to the notch
> Different slope angles
> Rounded slopes - convex or concave
> Spherical tip shape
>
> "Cheap Chinese jacks"
> Racism is appalling, no matter the form it takes.
> Re-posted from MuffWiggler:
> 'People complain endlessly about "that Chinese crap", but it would  
> not even
> be on the market if no-one bought it. When it comes to components, the
> motive behind production is fulfilling a customer's specifications.  
> Very few
> (relatively) component manufacturers are in the innovation area of
> manufacturing, most are bespoke or custom shops [This is  
> particularly true
> of Asian manufacturing]. Nearly all of the components that they  
> offer were
> originally design by someone else for their own product line and,  
> once the
> orders are filled, the component manufacturer still has all the  
> tooling for
> that product, so they make it available to others.'
>
> It wouldn't be available if people would just stop buying it! So  
> where does
> the blame truly lie? Furthermore, much of the "crap" manufactured in  
> China
> is designed by companies in other countries. China just gets the  
> blame again
> - *for making what they were told to make*.
>
> Best regards,
>
> ~flight
> flight at flightofharmony.com
> http://www.flightofharmony.com
>
>
>
>
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