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The Best 500 Series Chassis/Rack/Lunchbox Enclosures

by | Mic Preamps | 1 comment

500 series modules are an increasingly popular option to buying full-size rack gear or freestanding desktop/tabletop units.

Because of the demand, manufacturers are making more and more units available in the 500 series format.

No matter what type of module(s) you purchase (and they are addicting once you start!), you’ll need an enclosure to house it in.

The first part of this article goes into detail about how to choose the right enclosure.

The second part features reviews of the best 500 series enclosures.

500 Series Enclosure Basics

500 series modules are housed in a powered enclosure, sometimes called a chassis, rack, or lunchbox.

Chassis and racks are designed to be rack mounted, while a lunchbox is designed to be portable (its look and carrying handle are reminiscent of a lunchbox.)

The enclosure serves a few purposes:

  • It provides power to all modules, including 48V phantom power
  • It provides connectivity to all modules through XLR, ¼ ”, and/or DB-25 inputs and outputs
  • It provides a secure housing to protect modules from damage

Some enclosures also provide stereo linking or audio summing capabilities.

What to Look For In A 500 Series Enclosure

The most important things to look for in an enclosure are:

  • Compatibility
  • Lots of connectivity
  • Lots of power
  • Compatibility with older 500 series modules


Modules are connected via a rear-panel 15-pin card that fits into a slot in the enclosure.

Until recently, enclosure compatibility with older 500 series modules used to be an issue.

But today, due to API’s VPR Alliance program,  most manufacturers adhere to the standardization and consistency guidelines for the 500 series format.

This means that some features like -/+ 16V rails and 1.5” X 5.25” slot sizes are standardized.

Still, it’s best to make sure any modules you are looking to purchase are compatible.

To check if a specific 500 series module is VPR approved, click this link.


The rear of the enclosure has all the connectors.  They are usually +4dB balanced inputs and outputs via XLR or ¼” jacks.

Some enclosures include 25-pin DB-25 connectors for connecting all channels directly with an audio interface, mixer, or other gear.


The enclosure supplies all the power to the modules.  Each enclosure will state the full amount of power it can supply across all modules.

Each module, depending on its design, will draw a certain number of milliamps (mA).

API’s original specs have 130 mA listed as the average draw per module.

Solid-state modules generally draw from 50 to 150 mA, while tube modules can draw 150 to 300mA.

The enclosures reviewed below run from 250 mA to 400 mA per slot, quite a bit more than the 130 mA spec.

Best 500 Series Chassis/Rack/Lunchbox Enclosures

Best 500 Series Chassis/Rack/Lunchbox Enclosures - Empirical Labs EL500

Empirical Labs is probably best known for their widely-used Distressor compressor and Fatso analog tape simulator/compressor.

Lesser known is that they also make a whole line of hardware and software products that provide innovative solutions to audio problems.

The Empirical Labs EL500 is one such solution.

Most 500 series enclosures/racks house at least 6 modules.

But, for studio owners who only need a couple of modules, the Empirical Labs EL500 is a perfect solution.

It’s a dual module chassis that’s housed in a single space rack enclosure.

Its affordable price and features make it a perfect fit for small home project studios.


Empirical Labs commented on the EL500’s development on their website:

“When ELI started making our own 500 series products, we looked at the power supplies on the market and couldn’t help but notice a need for a better single height dual module rack unit. 

On other single height rack units, the modules protrude from the front panel, and don’t look sturdy or attractive.

Power supplies were often noisy, frequently reducing the performance of any module mounted in them. 

Also, only XLR ins and outs were provided to the user, limiting the device’s applications.”

The EL500 they produced solved these problems.

Both modules are flush mounted for a clean look that also protects them from damage.

It also features a very quiet +/-16V power supply for optimal performance that provides more than 280mA of power to each module.

Two other features are 48V phantom power for condenser and some newer ribbon mics, and a Link switch that turns on stereo linking for the 2 modules.

For connections, it has balanced XLR and ¼” TRS inputs, balanced XLR outputs, and unbalanced ¼” TS outputs for flexibility in connecting mics or instruments.

Plugging a cable into the front panel’s auto-impedance-sensing instrument/DI input automatically connects to the left module’s input.  This is very handy for speeding up your workflow when recording.

And finally, the EL500 has a voltage selector switch for use in different countries.

Final Thoughts

The EL500 is an excellent choice for anyone planning on purchasing just a couple of 500 series modules.

The EL500 complies with API’s VPR Alliance specifications so it should work with virtually all 500 series modules.  However, it is always smart to check before purchasing any modules.

Empirical Labs EL500

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  • Two module 500 series powered chassis/rack enclosure
  • XLR and ¼” TRS inputs and outputs
  • Auto-impedance-sensing instrument/DI input
  • Very low noise 560 mA power supply
  • 280mA of power available to each module
  • Stereo link feature
  • 48V phantom power
  • 1U single rack space
Best 500 Series Chassis/Rack/Lunchbox Enclosures - Radial SixPack 500 Series Lunchbox Rack

The Radial SixPack is a portable 6-slot powered lunchbox style rack for 500 series modules.

It’s designed to be able to carried easily using the built-in handle, or it can be rack mounted with the optional flanges (sold separately).  It takes up 3 rack spaces in a standard 19”rack.

The SixPack has become a studio favorite by hit producers like Joe Barresi, Kevin Churko, and Joe Chiccarelli.

Numerous reviews in music magazines like Mix Magazine, Recording Magazine, MusicTech, and Electronic Musician have given it positive reviews for its design, features, and versatility.

In terms of compatibility, the SixPack works with current and older 500 series modules and is 100% compatible with the older API pin format.  It meets the VPR Alliance specification for 500 series standardization and consistency compatibility.


The SixPack is built with heavy 14-gauge steel which not only protects the 500 modules from damage but provides shielding from RF/magnetic fields.

It’s designed with a 1600 mA supply that supplies over 265 mA of current per slot.

The 500 series specs call for 130 mA, so plenty of power is available for modules that draw a lot of juice like tube mic preamps.


The front panel has 2 XLR inputs for ease of connecting mics.  These inputs can be routed to inputs 1 and 4 or can be routed to channels 7 and 8 on the D-Sub connector.

The rear has both XLR and ¼” TRS inputs and outputs.  The XLR jacks are wired in parallel to the ¼” connectors, allowing them to be used as mults or for cross-patching modules together for creative uses.

Two 25-pin D-Sub connectors make connecting to an audio interface or mixer a snap.

A Feed switch allows you to connect one module to the next.

Additional Features

On the front panel, the SixPack has indicator LEDs for power and 48V phantom power.

On the rear, it has a Stereo Link switch that works to link two adjacent channels for stereo processing.

There is also an Omniport ¼” TRS jack that can be used to access additional functions, depending on the module connected.

For example, Radial’s PowerTube mic preamp uses it for an instrument DI.

This functionality is determined by the module’s manufacturer; a growing number of companies, including Grace Design, Purple Audio, and Serpent Audio, support Omniport.

Finally, the SixPack comes with a built-in safety feature that protects the rest of the connected modules from damage if one malfunctions.

Final Thoughts

The Radial SixPack packs a lot of features into a 3U (3 rack space) size enclosure.  Solidly built and with plenty of power and connectivity, it’s an excellent choice for any studio.

Radial Six-Pack 500 Series Lunchbox Rack

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  • Six module 500 series powered chassis
  • XLR and ¼” TRS inputs and outputs
  • 2 front panel XLR inputs
  • 1600 mA supply
  • 265 mA of power available to each module
  • External power supply
  • Stereo link feature
  • Two D-Sub connectors for DAW/ audio interface connections
  • 48V phantom power
Best 500 Series Chassis/Rack/Lunchbox Enclosures - Lindell Audio 506 Power
Best 500 Series Chassis/Rack/Lunchbox Enclosures - Lindell Audio 506 Power

Lindell Audio is a Swedish manufacturer of mic preamps, compressors, EQs and more.

The company was started in 2010 by record producer Tobias Lindell (Europe, Mustasch, Hardcore Superstar) as a way to outfit his Bohus Sound Studios with top-quality gear that was not available anywhere.

The Lindell Audio 506 Power holds up to six 500 series modules in a compact enclosure that is easy to transport.

It’s a very cost-effective way to house and power your favorite 500 series modules.


The 506 is a no-frills unit.

The front panel simply has slots for 6 500 series modules.

The rear panel has balanced gold-plated XLR inputs and outputs for each channel, as well as D-Sub input and output connectors.

The no-noise external +/- 16V, 2400mA power supply provides 400mA per slot, more than enough to run power-hungry tube modules.

48V phantom power is also included with a status indicator LED.

Overload and short circuit protections are included to protect connected modules from damage in case one malfunctions.

Final Thoughts

The Lindell 506 is highly recommended for anyone wanting a no-frills portable enclosure that more than adequately does the job.

Lindell Audio 506 Power

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  • Six module 500 series powered chassis
  • Balanced gold-plated XLR inputs and outputs
  • D-Sub input and output connectors
  • Overload and short circuit protection
  • No-noise external power supply
  • +/- 16V, 2400mA supply
  • 400 mA of power available to each module
  • 48V phantom power
  • Lightweight but rugged aluminum enclosure
  • Includes neoprene travel bag
Best 500 Series Chassis/Rack/Lunchbox Enclosures - API 500-8B Lunchbox®

API, a pioneer in top-quality recording consoles, mic preamps, and other studio gear, is no stranger to the pro audio community.

From their groundbreaking analog consoles in the early 70s to their cult-like status today, the “API Sound” is coveted by both pro and home and pro studio owners alike.

API was instrumental in developing and commercializing the 500 series modules concept of modular rack-mounted units powered by a “lunchbox” chassis.

Technically Lunchbox® is API’s registered brand name, but many people call any 500 series enclosure a “lunchbox.”


The API 500-8B Lunchbox (listed on API’s site as the 8 Slot High Current Lunchbox®) is an 8 slot powered portable lunchbox rack.

It features full compatibility with all API 500 series modules and VPR-approved modules.  VPR is API’s VPR Alliance,   a program of standardization and consistency guidelines for manufacturers wishing to design products for API’s 500-series rack format.

The unit has rubber feet and can be placed on a desktop or console, or rack mounted with an optional Rack Ears kit.  It also features a carrying handle for mobile use.

The front panel has the six slots, plus a left side panel with indicators for +16V, -16V and 48V phantom power.

On the rear panel, inputs and outputs are only available through D-Sub connectors.  You will need a D-Sub to XLR snake, or D-Sub to ¼” TRS snake.  Approximate price for each is $50.00

The rear panel also has a set of 8 switches for channel linking.

Power rails with individual fuses keep any malfunctioning module from damaging other modules.

The power supply is external, to reduce noise, and each slot has 250mA of current available, for a total of 2,000mA of power.

The LB-8B also provides 48V phantom power to all modules.

Final Thoughts

The API 500-8B Lunchbox is perfect for mobile recording or in-studio recording sessions.

With 8 slots, 250mA of power for each module, compatibility with VPR-approved modules, and channel linking capability, the 500-8B is a cost-effective way to get the most out of your 500 series modules.

API 500-8B Lunchbox® (8 Slot High Current Lunchbox®)

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  • Eight module 500 series powered chassis
  • D-Sub input and output connectors
  • External power supply
  • +/- 16V, 2,000 mA supply
  • 250 mA of power available to each module
  • 48V phantom power
  • Power rails with individual fuses keeps a malfunctioning module from damaging other modules
  • Rugged steel chassis
  • Rack mountable with optional Rack Ears kit