Flawn, you wrote,
>The only applications I've seen for 4-conductor mini plugs are two:
>
>1) A four conductor metal jack on my iBook which, with the right adapter
>cable, gives Video out on the tip, left and right audio on the first
>and second
>rings, and ground on the sleeve
>
>2) Mini jacks where there are three metal contacts for analog TRS mini
>plugs, but when a longer plug is inserted the same jack serves as an OPTICAL
>digital input.
>
>Might the latter be the case in the drawing you're looking at?
There's a detailed picture in the user's manual. It clearly shows
that the tip and ring are in the same positions, and are left and
right +, but the longer shaft area behind them is divided into two
segments, labeled left - and right -.
The recorder has a combo input jack, but the output jack is only
analog. This is the first time I've seen a 4-conductor mini stereo
connection.
If a standard 3-conductor mini-stereo plug is inserted into this
jack, the left and right - will both go to the common (shield). So
it's compatible with standard cables. My guess on why they supply the
4-to-3 cable is that the amp is designed to drive significant current
into low impedances. It might be in danger of destruction if shorted,
so they put a protective pad in the adaptor cable.
A way to test this hypothesis would be to plug standard headphones
into the output jack directly, and then through the adaptor cable and
compare the levels. If the level drops with the adaptor cable, it's a
pad. The level wouldn't necessarily drop when the adaptor was used
with the line input of an amplifier, because the input impedance
there is much higher than headphones, and a simple series resistance
would have little effect.
-Dan Dugan
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