WHAT IS 500 SERIES?  (Part 1/2)

1. WHAT IS THE 500 SERIES?

1.1 THE FORMAT.

The "500 SERIES" is an audio module format, with 3 rack units (1 rack unit is equivalent to 44.45mm) high (133.35mm) by 1.5 inches (38.1mm) wide, and 150mm deep, as mic/line preamps, equalizers, compressors, and really any function you can think of that might be useful in audio recording or mixing.

This format was invented by an American audio company API (Automated Processes, Incorporated) in the late 1960s. At the time, some mixing engineers using API consoles wanted to have some of the equalizer and preamp modules, so they could take them to the studios where they were called to record or mix. For this reason Saúl Walker, founder of API, devised a format of modules, which were integrated into metal boxes that integrated the input and output connectors and a power supply. In this way, the 500 SERIES format was born. Originally they were racks with 6 or 8 bays for modules, although now most models integrate up to 10 modules in a 19" rack.

Example of Rack series 500. Model MIDAS L10.

1.2 THE RACK

500 series rack. MIDAS L-10. Power switch and indicator light.

Here we already begin to see some interesting details.

In this 500 series rack model, MIDAS L-10, the power supply is integrated into the rack itself. It is a bipolar switched power supply, which delivers the necessary voltages and currents for all modules to work with guarantees. The voltages are as follows: +/-16volts and +48v for phantom power. The current it supplies is about 3 amps. Enough to power 10 modules.

We can also see the "Backplane" connectors, where you have to insert the edge of the module card, so that it receives both electrical power and audio signals can enter and exit the modules that we have installed.

1.3 THE CARD EDGE "CARD EDGE CONNECTOR".

It is very important to know what function each one of the pins of the modules that we insert in a 500 series Rack performs. In the case of the MIDAS L-10 Rack:

FROM TOP TO BOTTOM

PIN 1: CHASSIS GND

PIN 2: BAL OUT + (+4dbu)
PIN 3: UNBAL AUX OUT + (-2dbu) NOT USED
PIN 4: BAL OUT - (+4dbu)
PIN 5: AUDIO GND
PIN 6: COMPRESSOR STEREO LINK
PIN 7: UNBAL AUX OUT - (-2dbu) NOT USED
PIN 8: BAL INPUT - (+4dbu)
PIN 9: UNBAL AUX IN - (-2dbu) NOT USED
PIN 10: BAL INPUT +(+4dbu)
PIN 11: UNBAL AUX IN + (-2dbu) NOT USED
PIN 12: +16V
PIN 13: PSU GND
PIN 14: -16V
PIN 15: +48V PHANTOM

Notice the card edge of the preamp J.A.K. AUDIO 9K242. The top pin is #1 and the bottom is #15.

1.4 THE BACK OF THE 500 SERIES RACK

Here on the back panel, is the place where we will make the connections so that we can record the audio signals and take them to other modules or to the DAW.

To begin with, let's note that this particular rack, unlike the standard 500 series models, has 4 rows of audio connectors, instead of the usual 2 rows. Let's describe them:

FIRST ROW (TOP ROW):

Above all: MALE XLR connectors for SIGNAL OUTPUT of the 500 series module that we have installed. This signal output is what we will record in the DAW or take to other module(s) to process the signal.

The COMP BUS BUTTON: Is used to connect the Sidechain circuit of two mono compressors, so that by altering the controls on just one of the compressors, you can affect both compressors. Very useful for compressing in stereo.

LAST ROW (BOTTOM ROW)

At the bottom: XLR FEMALE SIGNAL INPUT connectors of the 500 series module that we have connected. Here we will connect a microphone or balanced line level signal.

AUDIO 8-9 and AUDIO 9-10

These buttons on the back allow you to chain the output of one module to the input of the next, and so on, as far as your 500-series rack allows. In this case, as it is a rack of 10 units, you can chain up to 10 units. Many times you want a preamp, an equalizer, and a compressor. That's three units. All you have to do is press the AUDIO 1-2 and 2-3 buttons, and you'll have a chain with three modules. If you only want two modules linked, press the AUDIO 1-2 button. It's that simple! Later, when the installation becomes complicated in your studio, you will see that a patchbay will be very useful for creating all kinds of audio chains.

THE MIDDLE ROWS (SECOND AND THIRD)

On most 500 series racks, you will never find these connectors. They are not used...much. A 500 MONO series module has one input and one output. End of story. But it is true that having a rack with this type of connectivity can inspire very creative ideas. Stereo modules in a single bay, or independent inputs and outputs for modules containing an equalizer and a compressor... etc. The limit is your imagination!

So far the first part of the introduction to the 500 SERIES. In the second part I will talk about integration with the DAW and the various possibilities that this entails. Until the next Article!!

J.A.K. AUDIO 10/18/2022.