Here's another product from Radial Engineering that has much more to it than meets the eye. At first glance, the Workhorse SixPack has the same form factor as any other six-slot 500-series frame with a carry handle, like the API Lunchbox, the product that defined this popular format. But if you look closely, you'll see that the SixPack has two XLR inputs on its front panel and a bunch of extra connectors and switches on its back. 

Let's start with the back. As you would expect, there are XLR jacks for six channels of I/O. If you want to use the SixPack like any other 500-series frame, connect your cabling to the XLRs, plug in the external power supply, and you're ready to go. But then you'd miss out on all the fun! 

Between odd and even slot pairs in the back are Link switches. These allow you to "link" adjacent pairs of modules that support link functionality for stereo processing — no need to move internal jumpers or solder across points on the SixPack's backplane. Between all the slots are Feed switches. These allow you to easily tie module outputs to the inputs of the next modules up — without using patch cables — to quickly chain multiple modules into "channel strips." For example, you can "feed" a mic preamp in slot 1 to an EQ in slot 2, then to a compressor in slot 3, just by enabling the appropriate Feed switches. The input of your channel strip would then be the input of slot 1, and the output would be the output of slot 3. Meanwhile, if you wanted to also record the pre-compressed signal (for parallel processing or for a safety), you could take the output of slot 2 and patch that into your recording device. These Link and Feed switches are signature features of the whole Radial Engineering Workhorse line. 

In addition to the XLRs, there are also 1/4'' TRS I/O jacks on the back of each slot. These parallel the XLRs, so if you have TRS snakes, you're good to go. Even better, if you have TRS patchbay cables (which are more ubiquitous than short XLR cables), you can patch to your heart's content — between slots on the SixPack or even between the SixPack and your patchbay. With two easy-to-patch outputs per module, being creative with your parallel processing chains couldn't be simpler. 

Another Workhorse signature feature is the 1/4'' TRS Omniport, which is present here on every slot. Different modules utilize the Omniport for different functionality. For example, the Radial EXTC guitar effects interface uses the Omniport for an extra insert loop, and the Radial PowerTube preamp uses it for an instrument DI. The Omniport is well-documented in Radial's WhosDoc (Workhorse Open Source Document), and many 500-series modules from other manufacturers support the OmniPort function, including modules from Grace Design, Purple Audio, Serpent Audio, etc. 

Moreover, there are two DB-25 jacks in back for easy connection to your workstation or studio patchbay using standard TASCAM-pinout eight-channel snakes. And yes — the SixPack is a six-slot frame, but the propeller-heads at Radial Engineering figured out how to put the two extra channels of the DB-25 jacks to good use. For starters, two additional TRS jacks on the back panel, labeled 7 and 8, break out the outputs of the extra DB-25 channels. And remember the two XLR jacks on the front? Those are the inputs for the extra channels. But it gets even cooler than that. 

Two switches allow you to re-route the front-panel XLRs to slots 1 and 4 of the SixPack, independently or together, so you can quickly create one or two channel strips (e.g., 1-2-3 and 4-5-6) that you can feed from the front. Or, using two more switches, you can route the front-panel XLR inputs directly to 

two extra XLR outputs on the back, also labeled 7 and 8, so you can internally send signal from the front XLRs to the rear XLRs, and then patch into the inputs of any of your slots, or even into Omniports using the right adapter cables — or to a completely different piece of gear altogether. And, if you'd rather just leave the front XLRs alone, there are extra XLR inputs for 7 and 8 in the back too, and with a flip of a switch, you can connect each of these to its extra DB-25 channel (in parallel with its corresponding front XLR). This "all-rear" routing configuration makes it easy to patch the two extra channels of your DB-25 output snake to some other piece of gear (or to Omniports) and then back into the extra channels of your DB-25 input snake. Yeah, crazy flexible! 

Even the carry handle of the SixPack is more than what you see. You have the option of mounting the handle on the long "top" face of the chassis or on the short "side" (top and side depend on how you look at the SixPack). The four included rubber feet can be mounted on the opposite face accordingly. Or, if you really want to get tricky, you can even choose vertical orientation for carrying, but horizontal orientation for tabletop placement — which is what I did. (I plan on ordering an extra handle and another set of feet from Radial's parts department so I can have two handles and all eight feet permanently mounted for all possible carrying and placement configurations.) 

The SixPack presents lots of options, so you do have to exercise care when utilizing some of its features. For example, each Feed switch, when enabled, does not electrically disconnect its corresponding XLR and TRS input jacks. These input jacks remain connected to their module, so if you patch anything into these jacks when you've got their corresponding Feed switch enabled, you'll be effectively wiring two (or three) outputs together into one input (which is usually not a good thing). Also, the switches and XLR breakout jacks for DB-25 channels 7 and 8 are in my opinion poorly labeled (and the product manual's incomplete explanation of this feature set doesn't help). The F and M labels for the jacks and switches call out which jacks are female and male, something that's already obvious, but these labels fail to make it obvious which rear XLR jacks are connected (or not) to the DB-25 channels when you flip the routing switches. I had to figure this out using a multimeter. 

There are many other features worth mentioning. The external power supply is rated for 1600 mA, which averages to twice the per-slot current specified by the original 500-series specification. Chassis and electrical grounds are separate, and there's a ground lug on the back of the chassis. The backplane is a mil-spec PCB with a full ground plane and through-hole parts; and it includes protection circuitry to reduce the chances of a module with an electrical fault damaging adjacent modules or the SixPack itself. Radial ThumbSet thumbscrews are included for mounting modules in the frame — no need to find a screwdriver when you're swapping modules. An alignment tray inside the frame facilitates insertion of 500-series modules from Radial and some other manufacturers. (I removed the tray, because some of my non-Radial modules wouldn't fit otherwise.) Optional "ears" for mounting the SixPack in standard 19'' racks or into desk cutouts can be purchased separately. I'm sure I'm missing many more features unique to the SixPack (or to the whole Workhorse line), so visit the Radial website for more details. 

All in all, I'm a very satisfied owner of the Radial Engineering Workhorse SixPack. I think it's the best six-slot 500-series frame available. In fact, I've been a fan of the whole Workhorse line ever since I purchased the original eight-slot Workhorse frame and mixer five years ago. Since then, I've added the ten-slot Powerhouse and the three-slot Cube and Powerstrip frames to my 500-series collection. And now I own a SixPack too. 

Tape Op is a bi-monthly magazine devoted to the art of record making.

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