| I don't know a whole lot about patchbays, since I don't own one *YET*
but might be able to get you closer to what you're asking.
What you might have is a "Normalized" Patch Bay. As best as I know
right now, each input jack has a coresponding output jack. (I'm not
shure it there are common busses though.) When you patch something
from the front panel to another jack, you break the connection from
the source jack; and then connects to another via the cable. I'm
going to have to look this one up in my recording book.
Please correct me if I'm wrong.
JOhn
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|
Jeff,
I think I covered patchbays briefly in the "19 inch rack" note.
I'll have to look for the note and post a pointer. At any rate, patch
bays can be configured differant ways to suit your needs. I'm not
sure how your patchbay works specifically but in general, they work
like so:
The top and bottom jacks form a pair which can be configured in
one of the following ways:
Normalled - In a normalled configuration, the signal makes a loop
from top-rear to top-front, to bottom-front, and back across to
the bottom-rear. If you plug a jack into the top-front plug you
break the connection between the top-front and the bottom-front.
An example of where normalled loops work great is when connecting
the outputs of a mixer to the inputs of a tape recorder. The signal
from the mixer is connected to the top-rear and the output to the
recorder is taken from the bottom-rear. This allows you to "insert"
an effect processor. You connect a cable to the top-front (this
breaks the normalled loop) and connect this into the input of the
effect. The output of the effect is fed back into the bottom-front
and the insert is complete.
Normalled (* = signal)
_________________
top-front =|***************|= top-rear
|* |
|* |
bottom-front =|***************|= bottom-rear
-----------------
Non-Normalled - When a pair is set up in a non-normalled con-
figuration, the signal travels from front to rear on both the upper
and lower pairs, but there is not connection between top and bottom.
The top and bottom pairs are independant from each other. If you want
to keep signals isolated (like preamp inputs/outputs, guitar inputs,
etc) you must have the top and bottom jacks in a non-normalled
configuration.
Non-normalled (* = signal)
_________________
top-front =|***************|= top-rear
| |
| |
bottom-front =|***************|= bottom-rear
-----------------
Shorted - A shorted configuration allows you to use a top/bottom
pair as you would a y-cord. You could have one signal feeding
two inputs by shorting the two front jacks to one of the rear
jacks (or vice-versa).
Shorted (* = signal)
_________________
top-front =|***************|= top-rear
| * |
| * |
bottom-front =|****** |= bottom-rear
-----------------
There is a fourth configuration called half-normalled, which
allows you to tap off of the top-front jack and run a loop in
parralel with the normalled loop. Not all patch bays can run
this way.
If you have a 32-point patch bay, what you really have is 16
"channels". Each channel can be configured in either normalled,
non-normalled, 1/2 normalled, or shorted. For example you
could have the first 8 channels "normalled", the next four "non-
normalled", the next 2 "shorted", and the last 2 "1/2 normalled".
Tascam patch bays have 8 modules, each of which contain two channels.
One side has white jacks and the other has red jacks. To switch
from normalled to non-normalled you simply turn the module around.
If the red jacks are facing front, is it said to be normalled and
if the white jacks are facing front it is non-normalled, but this
is only when referancing things from the rear panel. To short a
channel you must actually solder a wire to the module (yech!!).
I'm not sure if Tascam bays can be used in a 1/2 normalled con-
figuration or not (I doubt it). Tascam patch bays are inexpensive
and work okay, but changing the configuration requres you to take
the entire bay apart and turn modules around. This tends to be a
pain, as you have to remove the bay from your rack, remove the
rack ears, pull the front and back covers off, unscrew the module
turn it around, and reassemble the whole thing. Soldering a wire
to a module to short it is pretty much a permanent change. I
wouldn't want to solder/unsolder it too many times as you would
inevitably end up burning etch and destroying a module if you do
this too many times.
Rapco makes patch bays which have a selector switch on the
front of each channel. The switch allows you to select any of the
4 configurations. They make a 48-point bay like this, and possibly
a 32-point bay as well. They're great bays, but costly. I priced
one of the 48 point bays, and it listed for $275.00. With a bay
like this I'd be real careful when flicking switches, as you may
inadvertantly send the wrong signal to the power amp, or cause
some other fiasco.
Of course there are also "midi-patch-bays" out there which do
all of this electronically and are programmable. This is a topic
for a differant note.
Hope this helps !!
Mark Jacques
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