ProCo PM148 48 Point Configurable Patchbay
Last Update 07-08-2025
Early in my studio
development, I saw the practical use of a patchbay so the
ProCo PM148 (now out of production) was an early acquisition.
My current studio now has three of them. My studio was largely
finished and completely OTB before "ITB" and "plugins" became
popular, so this discussion will concern hardware.
A small studio could start with MIDI modules/synths, a mixer, and
one or more effects. As you add more toys to your studio, the
added cabling gets unmanageable. The practice of changing
cables from from the rear panel of synths, effects, et al that can't
be accomplished with the mixer becomes cumbersome. Enter the
patchbay.
A patchbay has jacks on the front and the rear. The idea is to
route synths, mixer, and effects I/O to the rear panel of the
patchbay, which are propagated to the front panel jacks. The
front panel jacks permit connections using patchbay cables without
fiddling around the backs of the devices with a flashlight.
You have the flexibility to "fix" the routing of device A output to
device B input, or changing any routing. It is a great space
saving tool.
The first thing you do is PRE-PLANNING, deciding on the connections
of the patchbay. I have changed my routing more than once in
the growth of my studio, so plan for revisions. The PM148 is a
"48 point" patchbay meaning there are two rows each with unbalanced
24 channels, both front and rear. The top row is "A" points,
the bottom is "B". It is also configurable in that it lets you
set the relationship between "A" and "B" of each channel - open,
parallel, normal, or half normal. There's a four position
slideswitch accessible from the top and bottom that lets you set the
configuration.
"Open" simply means that "A" and "B" are not connected (used for
device outputs, which are NEVER connected together).
"Parallel" means the front and rear "A" and "B" points are connected
(think of it as a "MULT" module in a modular synthesizer).
"Normal" means that the front panel "A" point is connected (or
"normalled") to the "B" point, where a plug inserted in either "A"
or "B" interrupts the connection. Use this to "normal" an
output of a source to the input of your preferred effects device,
which leaves the option is routing the source to another effects or
plugging a different source into the effects input.
"Half Normal" means that the front panel "B" point is "normalled" to
the "A" point, such that when nothing is plugged into the "B" point
it is connected internally to the "A" point. One use is for stereo
mixers, where you can connect a mono device by plugging into only
the "A" point (assigned as left input of mixer channel) and it is
automatically routed to the "B" point (assigned to the right input
of mixer channel). Another use is for stereo effects return
which allows a mono effects device to be used.
I included a sample
configuration from my studio - slightly outdated but
sufficient for illustration. Items in bold are synth outputs
(I build my own I/O panels with input jacks for external synths like
my Memorymoog
routed to the rear panel of the patchbay). This is a good
example of pre-planning. Notice that the eight stereo mixer inputs
of the SM-82 (configured as
"half normal") are centered in the middle. The left half are closest
to the synth outputs on the left, the right half closest to the
synth (or effects) outputs on the right. I use short patchbay cables
to connect synth outputs to mixer inputs. This arrangement prevents
the "rats' nest" of patchbay cabling. I like my Moog Source
through my Korg SDD-1200 dual
digital delay, so I exploited the "normal" configuration to
make the routing without a patchbay cable, then use patchbay cables
to route SDD-1200 outputs to the mixer inputs. I like my Korg
SDD-3300 triple digital delay in the FX loop of the mixer; I
use patchbay cables to route effects send/return to the SDD-3300,
but I have the option to use some other effects in the FX loop
instead of the SDD-3300. Not all the effects outputs or inputs
on the patchbay are used, but are available for future.
One pre-planning benefit of my patching system is when I have a song
ready for recording, I route the synth (or effects) outputs to a DI
box which connects to my Alesis HD24 hard disk recorder
for further song development with non-MIDI sources such as vocals,
guitars, etc.
The PM148 is supplied with blank labels - with adhesive on the back
- for labeling points. But I foresaw that my cable routing
would not be static, and I hate the gooey residue left behind when
tape is removed. Since the frame is ferrous metal, I opted for
magnetic labels on the channels instead of adhesive labels. I
made point labels using card stock paper (or business cards flipped
over with the blank side on the back) attached to business card
magnets; I cut them to size then apply them to each channel.
On each label I use a color labeling convention that tells me which
whether the point is input (blue) or output (red) - quick glance
eliminates guesswork.
I haven't changed the configurations or layouts of my PM148s for
over ten years. The only trouble they have given me is
occasional oxidation of the jack contacts - this is easily solved by
periodically (about every 5-7 years) reaching in the back and
re-inserting each rear panel plug a few times (this will happen on
ANY patchbay, mixer input, effect jacks, etc). Today most DAWs
have internal patchbays that never oxidize, but I built my system
and am not anxious to learn a brand new one.
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