dbx PB48 User Manual

PB-48 Patchbay

INTRODUCTION

UNDERSTANDING PATCHBAYS AND THE dbx PB-48

(1-A) Full-Normalled or Half-Normalled Patchbay (1-B) Half-Normalled [Mult-ed] Patchbay

(1-C) Half-Normalled Patchbay (1-D) De-Normalled Patchbay

[With Rear-Panel Normal Connection Broken]

Figure 1: Normalled, Half-Normalled and De-Normalled Patchbay Operation

The PB-48 is shipped from the factory with its circuit boards installed for half-normalled patchbay operation. Normalled means that audio signal automatically flows between a vertical pair of patchbay jacks without the need for patchcords (see Figure 1-A). Normalled patchbays may be halfnormalled or full-normalled. In the half-normalled PB-48, each rear-panel upper jack is respectively normalled to the jack directly below it as long as nothing is plugged into the lower front-panel jack. Half-normalled means that plugging into the upper front-panel jack does not break the connection between the upper and lower rear-panel jacks, but splits the signal to two destinations, while plugging into the lower front-panel jack breaks the connection (see Figures 1-B and 1-C). Note: Afull-normalled

patch bay’s rear-panel connections are broken when plugging into either front-panel jack.

A simple example of using half-normalled operation: connect a mixer ’s monitor out to one of the PB-48’s rear-panel upper jacks, then connect the rear-panel jack directly below it to a power amplifier. The “normalled” signal will flow from the mixer monitor out to the power amplifier, and will only be broken when a connection is made to the corresponding frontpanel lower jack.

Congratulations on purchasing the dbx PB-48 rackmountable patchbay. The PB-48 features 48 front panel patchpoints and 48 rear panel patchpoints, from 24 user-adjustable board assemblies that can be configured for Half-Normalled or De-Normalled patchbay operation without soldering or cutting wires. The PB-48 is a rugged, noise-free, patchbay designed to serve all your patchbay needs, from providing clear and easy access to your mixer and other studio gear, to reducing the wear and tear on their jacks, to facilitating quick and precise re-routing of devices within your studio setup. PB-48 patchbay jacks accept balanced TRS or unbalanced TS standard audio 1/4” plugs.

We recommend that you take a moment and read through this instruction sheet as it provides information that will assist you in using your patchbay to its fullest. Explanations of standard patchbay jargon, with plenty of pictures, are included to help de-mystify common patchbay points of entanglement and clear up any misunderstandings you might have. Examples, suggestions and tips are provided as a starting point only. Experiment with different setups, so that you find the setup that best fits your system.

SIGNAL FLOW

OUT

BACK

FRONT

SOURCE

TO LOAD

OUT

BACK

SOURCE

TO LOAD 1

FRONT

SIGNAL FLOW

FRONT

SOURCE 1

TO LOAD 2

OUT

BACK

SIGNAL FLOW

FRONT

OUT

TO LOAD 1

SOURCE

BACK

OUT

TO LOAD 2

(2-A) Unscrew rear panel nut and save it. (2-B) Push down on rear lower jack, and snap board out

(2-C) Keeping circuit board component side facing you, (2-D) Angle board in (front lower jack to lower front hole), and

rotate the board 180˚. push rear upper jack (in and up) to snap board into place.

(2-E) Re-tighten upper jack with nut from step A.

Figure 2: De-Normalled Configuration Steps (to Re-Normalize, repeat steps)

The front-panel upper jacks in a half-normalled/normalled patchbay are usually considered to be outputs because each front-panel upper jack is wired directly to its corresponding rear-panel upper jack, where the audio source is connected (see Figure 1-B). For example, in the half-normalled situation, connecting from a front-panel upper jack output to the input of a headphone amp allows you to “listen in” to the signal from the corresponding rear jack. This setup is sometimes called a Mult-ed patch, because the patchbay simultaneously routes the rear-panel signal (i.e., signal fed to the rear upper jack) to multiple points: one output to the rear-panel lower jack and one output at the front-panel upper jack. Apossible setup might have a mono mix sent to the rear upper jack, the routed signal at the lower rear jack fed to the power amp, and the routed signal at the front-panel upper jack connected to a tape recorder input for a mono tape mix.

The front-panel lower jacks in a half-normalled/normalled patchbay are called inputs because each front-panel lower jack is wired directly to its corresponding rear-panel lower jack which is connected to an equipment input. Plugging into a front-panel lower jack interrupts the signal fed from the corresponding rear-panel upper jack and provides a new input source to the rear-panel lower jack (see Figure 1-C). For example, inserting a DAT recorder signal into the front-panel lower jack routes the tape signal directly to the corresponding rear-panel lower jack. Note, however, that the front-panel upper jack retains the signal from the rear-panel upper jack.

The front-panel lower jack input can also be used to alter its corresponding rear-panel upper jack signal when the board assembly is correctly patched to a signal processor (e.g., an equalizer, compressor, gate, etc.). Start with a mixer and amp connected to one vertical pair of the patchbay’s rear-panel jacks, as described before. Then, connect the frontpanel upper patchbay jack (which has the mixer’s output signal) to the processor’s input, and connect the processor’s output to the front-panel lower jack input which feeds the amp.

To connect devices like effects or signal processors directly to the PB48’s rear panel jacks, so that they are accessible through a vertical pair of front panel patchpoints, the PB-48 must be De-Normalized (see Figure 1-D for example and Figure 2 for customization instructions).

In a De-Normalled (or Non-Normalled) patchbay, each front panel jack is routed directly and only to the corresponding rear-panel jack (i.e., first upper front to first upper rear, first lower front to first lower rear, etc.). The purpose for de-normalled patch points is convenience so that equipment rear-panel jacks are easily accessible. De-normalled operation is useful with effects devices or other input/output devices for which there is no “normal” connection between it and other equipment. For example, a compressor’s inputs and outputs may be patched into the insert point of any mixer channel or may be used on the master outputs at mixdown and, therefore, has no “normal” connection. Also, for consistency, the usual patch bay setup connects outputs to rear-panel upper jacks and inputs to rear-panel lower jacks, so normalling this vertical pair would cause an effects device’s output to be connected directly back to its input. This unintentional normalling is not only useless, but feedback from output to input can cause the equipment to oscillate and emit a nasty shriek.

Although a De-Normalled circuit board eliminates the opportunity to “mult” outputs, the number of possible “straight” signal connections is increased. For example, to provide access to all the inputs of a 16-channel mixer, connect the first eight pairs of the patchbay’s rear-panel jacks respectively to the 16 mixer inputs. Now, plugging a synthesizer into one of the front-panel patchpoints routes the synthesizer signal directly to the corresponding mixer input. Note that all of this can be accomplished using only 1/3 of the patchbay. The drawback, of course, is that any connection to a de-normalled patch point must be made with a patch cable.

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Note that when a board assembly has been de-normalled, a large “D: will be visible below the dbx logo at the bottom of the board assembly. For boards that are in the half-normalled configuration, a large “N” (for normalled) will be visible below the dbx logo. These “D” and “N” indicators are visible at the bottom of each board assembly even when the boards are secured in the patchbay frame.

UNSCREW

PUSH HERE

FRONT

PUSH IN AND UP

BOARD AFTER 180 ROTATION

(logo on bottom)

TIGHTEN

FRONT

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