How to rack any 500 Series Modules

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How to rack any 500 Series Modules

Postby owel » May 19th, 2016, 8:16 pm

This article first appeared on ... tructions/

So let’s say you want to own some 500-series lunchbox modules, could be a mic preamp, compressor, or equalizer unit. The problem is you don’t own a lunchbox rack. Even a blank 6-space rack can cost a pretty penny, and you still end up with no modules after purchasing the rack. Or, you’re just not digging the lunchbox form factor, and prefer a 1u 19″ rack unit. What do you do?

Well, you can rack your modules and house them in a 19″ rack! All you need is a power supply, and a little bit of wiring for the input XLR and output XLR connections.

What you’ll need:

You’ll need a 19″ rack case for this project. You can purchase racks from eBay, Amazon, Par-Metal, Modulo, Hammond, etc. My suggestion is choose a rack that is totally collapsible. By that I mean, the 6 sides of the rack can be disassembled, that way you can easily drill/machine/cut any hole opening you need on any of the six independent panels. For the rear panel, you’ll need to drill holes for the XLR jacks, and a square cutout for an IEC AC inlet connector, and the fuse holder.

For drilling the XLR holes, you’ll need a step drill bit to create these holes. First, drill a 1/2″ starter hole using your drill press/hand drill. Change to a step drill bit, and enlarge the hole to the correct XLR size. When you’re done drilling the large hole, place your XLR connector and mark the diagonal holes for the machine screws, and drill with a 1/8″ bit.

For the front panel, you can take the easy way and just cut some rectangular openings for the 500 series modules to slide into. Drill two additional mounting holes using a 1/8″ drill bit.

For the base plate, you’ll need to drill some holes for mounting the Power Supply Board and Power Transformer. Hole locations and size depending on the PSU kit you’re using.

Power Supply Kit and Power Transformer

The official 500 series standard calls for +/-120mA max per module (these values may have changed and increased since the old standard). And since a 19″ rack can only hold (2) modules side-by-side, this power requirement is very easy to meet. Using a 30VA power transformer for example, will give us 830mA total amps, enough for our 2 channel modules. A 30VA power transformer (toroidal) is also small enough to fit inside a standard 19″ 1u rack high chassis.

You can use a FiveFish Power Supply Kit, PSU-2448 for this job. It’s perfectly sized, fits in a 1u rack height and the regulators are max rated at 1.5Amps per rail, more than enough for 2 total modules. The V+ and V- voltages are regulated and adjustable, and there is also a +48Volt power supply available for phantom powering duties.


If you buy a FiveFish Power Transformer kit, you get a 30VA toroidal power transformer (830mA), and also an IEC AC inlet connections, fuse holder, fuse, power switch and a Panel Mount LED indicator. But both the Power Supply and Power Transformer and get additional discounts.


Male XLR and Female XLR jacks
Your modules need to interface with the outside world, so you need some Male and Female XLR jacks. You can buy generic ones from eBay, or buy high-end, with gold-plated terminal Neutrik jacks. There are plenty of choices, from cheap to more expensive but high quality jacks.


EDAC 15-pin edge connector
How do we hook up the module to the power supply lines and XLR jacks? All FiveFish modules have solder pads near the card edge fingers. So you can solder wires directly to the board. But this solution is semi-permanent and does not allow for you to easily replace the module with another. An easier and more flexible solution is to use a 15-pin EDAC edge connector. Solder the wires to the edge connector, connect to your power supply and XLR jacks and plug the module to the EDAC connector.


Wiring Diagram
Here’s the wiring guide for all 500 series modules. I think it’s pretty explanatory.


Some additional notes:

Male XLR Pin 1 connects to GND/Chassis.
XLR OUT + connects to Male XLR “Hot”, Pin 2.
XLR OUT – connects to Male XLR “Cold”, Pin 3.

Female XLR Pin 1 connects to GND/Chassis. *** Important: This pin 1 needs to be also connected to power supply GND, otherwise 48V phantom power will not work.
XLR IN + connects to Female XLR “Hot”, Pin 2.
XLR IN – connects to Female XLR “Cold”, Pin 3.

GND means connection to power supply GND.
+48V connects to +48V output of power supply.
+16V connects to +16V to +18V output of power supply.
-16V connects to -16V to -18V output of power supply.
FiveFish Audio - DIY Mic Preamps & 500-Series Modules, API VPR Certified
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