Workhorse™ Development

Two years in the making… engineering challenges at every turn, lack of real standards, inconsistencies from one manufacturer to another, modules blowing up repeatedly and hundreds of thousands of dollars invested… the Radial Workhorse has been the most challenging project we have ever undertaken. We are finally there. The following discusses how the product came together and why we did what we did. 

For over 25 years, studio engineers have been enjoying the creative possibilities afforded by the 500 series (API Lunchbox™) format. The design consists of a rack than enables several modules to be plugged into a card-cage where they share the same power supply. The rack provides XLR inputs and outputs and 48V phantom powering for the modules. The simplicity of the design allows you to plug any module into another using conventional studio wiring. Modular, flexible… brilliant!.

Why is lunch so expensive? 
We figured that it was high time we got in the game and started to port over some of our direct box designs into the 500 format. We started with the JDV, Phazer and JDX. But as we delved further and further into the rabbit hole, we started to ask ourselves a host of questions: For instance: ‘why are companies like API charging upwards to $1000 for a rack, power supply and a dozen connectors?’  This seemed expensive. ‘Should these Lunchbox™ racks not provide more value?’ This got us thinking. For years, Radial has gained a reputation for delivering world-class performance at relatively affordable prices - ‘Could we not do the same by creating a new type of 500 rack?’

This led us to ponder how recording has changed and how one would interface analogue devices with today’s world of computers.  With more and more folks recording ‘in the box’ (the computer), it seemed that the conventional ‘patch-bay & mixer’ approach would not necessarily prove to be the best solution. ‘Why not allow the Lunchbox™ to act as a mixing console so that you could monitor the results right then and there?’  So we got to work…

How about an easy to use mixer inside the rack!
If you have ever tried to record using a Roland all-in one recorder you know how cumbersome it is. To turn on a reverb requires going through multiple layers, holding several buttons and then twisting a controller knob. It is absolutely painful.  Our idea was to create an easy-to-use device that could allow a bunch of mic preamps to be combined and then mixed together like an old school recording console. It had to be turn-a-knob simple. This would enable an engineer to maybe use a Radial JDV™ module for instruments, an API™ module for voice and or some other module to mic a guitar amp. In other words, you could build the perfect small format console of your dreams by simply plugging in the modules as needed.

This lead to figuring out how many modules would make sense. Some API Lunchbox designs could accommodate 4, others 6… some on the market as many as 10. It seemed that none of these were really designed to work within the norms of today’s computers… 8 channels seemed to make most sense. There are 8, 16 and 24 channel recorders, 8 channel converters, 16, and 24 channel mixers.

To create the mixer, we looked at traditional large format recording consoles like those made by Neve or SSL and what made them tick. We followed their lead using a traditional virtual ground mix buss and added Jensen Transformers on the main outputs to make sure the sound was as warm and smooth as possible. Since the Workhorse would likely end up in a live venue, transformer isolation would also help eliminate buzz and hum caused by ground loops.  An extra set of outputs was then added for monitoring.

Creating a smart listening environment
We figured that if you are intending to record a live band, a headphone mix is an absolute must. We then considered what happens in these situations and soon realized that sharing a single set of headphones is a pain. So we added a second headphone out so that the producer can listen in. The headphone amp also had to be stupid loud just in case AC-DC is on stage.

A major pain with so many workstations is in the inability to quickly sum a stereo mix to mono. This important feature lets you know if your stereo mix will translate properly on AM radio. So we outfitted the headphones with a mono sum as an extra benefit.

Adding as much connectivity as possible
By the time we worked out the space requirements to pack eight slots inside a standard 19” frame, we then had to figure out how to lay out the mixer. For it to be functional, it had to have eight volume controls with a left-right pan on each for stereo recording plus individual mutes. With eight channels, this opened the door to incorporating the Tascam D-Sub standard that has since been adopted by ProTools and so many others.

It also seemed clear from the outset that we had to retain the legacy of the original Lunchbox™ format so that older modules could be used. This meant having XLR inputs and outputs for each card slot. But this got us thinking… with so many products now using ¼” jacks, would it not make sense to also have some of these in the rack? So we added ¼” connectors to facilitate.

To add more even spice to the soup, we then added a LINK switch that would allow pre-configured left and right modules to be linked in stereo. Simple… now all we had to do was figure out how to route 174 traces on the back panel to the master section and make it all work without cross-talk or having the engineers leap out the window in frustration..

Feeding the beast without patch cables!
We then considered how the Workhorse would be used in various applications. What if someone wanted to create a stereo channel strip? You would select four different modules from a choice of preamps, limiters, EQs and compressors then simply plug them in. But how would they connect together?  In the past, folks had to wire each one using a bunch of XLR cables. Expensive and messy. Why not simply incorporate a switch?.

To this end, we added a ‘FEED’ function that allows one module to feed into the adjacent module (left to right) which in turn is routed to the summing mixer in the master section. This means you can feed one module into the next while retaining all of the connectivity options. Think about it: You can create the ultimate recording strip and are still able to mix-in the direct sound from each module if so desired. Stupid cool..

Retaining the API legacy with a built in summing mixer
We then asked ourselves: ‘How can someone take advantage of the built-in summing mixer when using old API™ modules?’ This led us to incorporating a dedicated 8-channel D-Sub connector that would enable folks to connect the output from an individual module directly to the summing mixer using a standard D-sub cable. This not only opens the door for individual modules to be ‘hot wired’ into the mixer, but allows the Workhorse to be used as a line-level analogue summing mixer for those that prefer to mix outside of the box. (And those great sounding Jensen transformers will surely add plenty of analogue warmth to those digital tracks.)

Expanding the Workhorse for more channels
We then thought: ‘With all of this routing and mixing power, folks may want to expand the system to 16 or more channels’.  To address this eventuality, we added a stereo expansion buss.  This way, you could sub one Workhorse into another using simple guitar cables and expand the system as needed. This not only allows someone to create a 16x2 or even 24x2 mixer, but each Workhorse could be treated like a sub-group while still enabling the engineer to tap the direct feed from each module for larger more demanding live recording sessions...

By using a similar approach to that employed by Rupert Neve Designs™, we once again brought another level or compatibility and standardization to the market. This is detailed in the Workhorse Open Source Document.

The Omniport – an open invitation to creativity
This got us really excited… and we figured with all of these features, other module manufacturers would quickly adopt the Workhorse as their rack of choice. In return, we wanted to give them the option to have their module do something unique. Omniport was born. Omniport is basically a TRS jack that can be used for anything. The module designer can use it as a key input, guitar output, footswitch, insert… who knows. The point here is opening up the design options to creative new ideas and greater flexibility.

Radial Module Omniport Function
PowerPre Instrument input
JDV Direct box output (low Z out for live touring)
X-Amp Instrument input
Phazer Balanced direct out (original dry signal out)
JDX Direct box output (low Z out for live touring)
EXTC TRS insert for patch bay
Komit Key input

Mechanically sound engineering
Finally, we looked at the mechanical aspects of the older racks. If you have ever tried to ‘negotiate’ plugging in a 500 series module into one of the typical API™ card-slot, you will know that trying to line up the card edge to the slot can be both frustrating and unnerving. We felt that sliding in a module should be easy. So we added a slide-in tray with alignment guides. Easy enough. But with such poorly administrated standards, we discovered that most module manufacturers do not follow precise guidelines. Therefore while some companies follow API’s lead, most are close variations.

To address the problem, we made the guides extra wide and arranged the tray with 4 singles and two doubles. We also configured the tray so that it could be rotated to allow double-wides to be installed at the far left so that they could feed into the adjacent module (if designed to the new radial spec). We went one step further and decided make the tray removable so that all non-conforming modules could still fit.

A word about setting standards
We have all heard the old joke about standards:  ‘Audio designers love them so much that they invent a new one every day!’ This in fact is not too far from the truth. In our view, using a clearly defined standard creates a better environment for the end user as it allows you to buy a product from one manufacturer and have it work with another.

One of the single most frustrating aspects in developing the Workhorse was trying to decipher the so called standards. We chose to support the original API Lunchbox format even though the information provided by API was somewhat cryptic. During our field tests, we found that some module manufacturers employed slightly longer card-edge connectors which would cause the module to stick out the front. We also found some that were shorter which could end up with a poor connection. Not good. This of course forced us to redesign the Workhorse a few times until we could find a relative balance.

To help solve the problem and help establish a common standard, we chose to produce the Workhorse Open Source Document that details all of the pertinent electrical and mechanical specifications. Our hope is that all 500 series manufacturers will eventually use this guide to follow suit. This free document is available by simply sending an email request to:

So there you have it… two years later… we took a proven concept and turbo-charged it with features and functions that are optimized for today’s recording environment and bulletproofed the functionality so that it should work properly in any environment. We think you will be blown away.

The API Lunchbox™, the VPR Alliance and the Workhorse Open Source Document

Lunchbox™ is a Trademark of Automated Processes Inc. The API Lunchbox first made its way into the market back in the 1980s. The concept allowed various console modules to be pulled out of their frame and used independently in a smaller rack known as a Lunchbox. The Lunchbox allowed the user to connect to-and-from modules using XLR or ¼” connectors that were mounted on the rear panel while sharing the same power supply. These could then be connected to a studio patch bay or ‘hard patched’ together using standard XLR cables. The format proved to be very convenient but only recently has it gained wider appeal. This we believe is due to the accessibility of high performance digital recording systems and the recent shift to smaller, more agile recording studios.

API created the VPR Alliance as a means to ensure modules from other manufacturers will fit properly and not harm API Lunchbox racks or modules when they are connected together inside a Lunchbox. To be ‘API Approved’ the manufacturer needs merely to send their module to API where they will check the mechanical spec and plug it in.  Although Radial is not a member of the VPR Alliance, we believe that the intention is good and valuable, particularly for smaller manufacturers that may not have sophisticated 3D modeling design systems that can ensure the product meets a precise specification.

The Workhorse and all Radial 500 series modules have been carefully designed to meet the original API specification and we have tested our products for compatibility with other racks such as those made by Purple Audio and modules of all types from various manufacturers.

To further support the API standard, we have published what we call the Workhorse Open Source Document. This details all of the mechanical and electrical specifications for the Workhorse and clearly defines the backward compatibility to older API rack systems. Our hope is that this comprehensive document will eventually guide manufacturers as they bring new and exciting products to market.

Legal Disclaimer

API, Lunchbox, Rupert Neve Designs, Tascam, ProTools, Purple Audio and other brands or trademarks mentioned on these web pages are in no way associated implied to be associated with Radial Engineering Ltd.  These brands and trademarks are the property of their respective owners and are only presented on this web site as a means to provide users with a point of reference. Any opinion or suggested application that involves these fine brands or trademarks are stated as our opinion only and should not be considered to be factual beyond the scope and intention as described herein.