CB Electronics XP-Relay

The XP‑Relay combines CB Electronics’ sophisticated patchbay control system with the purest possible signal path.

Regular readers will know how impressed I was with CB Electronics’ XPatch 32, which I reviewed in SOS August 2021 — in fact, I stated that “if I were in the market for such a device right now, I’d be buying this one.” The XPatch ecosystem has grown better since then, too. Not only have the promised higher channel‑count versions become available, but the software control app is more intuitive and feature‑rich. As with their main competition, notably Flock Audio’s Patch, the XPatches employ active electronics and the routing is performed using amplifiers.

There’s nothing inherently wrong with using amps for the switching, particularly if you exploit their benefits has CB did on the XPatch devices (CB achieved commendable noise and distortion figures, and the amps make possible both very fine calibration of each channel for each attached device and, since my review, level automation) but for some people the idea of anything other than a ‘straight wire’ connection between devices is anathema, particularly if they have no need of the extra functionality that active electronics can deliver. Such people should find CB’s latest product, the XP‑Relay, rather more enticing...

Overview

As the name implies, the XP‑Relay is closely related to the XPatches, but there are also fundamental differences in design and it joins rather than replaces them in CB’s range. Like the XPatches, it is a digitally controlled analogue routing matrix, and it’s controlled by the same XPatch app (which can communicate with up to four units of either type connected to the same Mac or Windows computer). But in this case the signal routing of the analogue signal is performed by relays, rather than amps, and the main benefit of this is that there is literally never anything more than a ‘wire’ connection between the inputs and outputs — just as would be the case on a traditional open patchbay. Also, the use of sealed relays means it should be less prone to contact problems than such bays, and unlike the XPatches it’s possible to pass through phantom power from preamps — and since all ‘pins’ make contact only with those of their intended destination there aren’t the same risks in handling phantom power as there are with a conventional jack patchbay. (As I’ll cover in more detail below, the XP‑Relay is itself also capable of supplying mics with +48V phantom power).

Of course, there are also some potential disadvantages compared with the XPatches. Since there’s no amplification or buffering you can’t apply gain offsets for different devices/channels, there’s no possibility of level automation, and you can’t, for example, route a guitar or bass DI to a line‑level device without involving other hardware to take care of the different levels and impedances. Also, the maximum channel count for the XP‑Relay is lower, since relays are bulkier and more expensive than amps, and other new facilities take up space on the inside and panels too. Currently, the maximum size of XP‑Relay, which is the configuration sent for review (I’ll discuss other options below), is a 16x16 matrix. It’s possible, though, to use the control software to link two such devices for stereo use, one unit handling 16 left‑channel signals and the other the corresponding 16 right‑channel signals. In short, they’re similar devices but not the same, and if you’re contemplating a purchase you’ll need to weigh the relative pros and cons according to your needs.

You need to use the software to specify what gear is attached and to set up your routing options, but thereafter use of the app to control the switching is optional.

As with the XPatch, the real ‘cleverness’ of the XP‑Relay, from a user point of view, lies in the XPatch control app. This has been updated frequently, and at the time of writing we’d reached XPatch version 4.4, which represents a significant improvement over v3.3 that I’d been evaluating when writing my XPatch 32 review. For one thing, it now supports drag‑and‑drop signal path configuration, which makes setup easier, but there are also plenty of smaller touches that combine to make it considerably more intuitive in general. You need to use the software to specify what gear is attached to what I/O and to set up your various routing options, but thereafter use of the app to control the switching is optional. You can use the software alone if you wish, but there’s now built‑in support for switching using an Elgato Stream Deck (see box), and the hardware can also be operated standalone, with support for MIDI control and footswitch‑based preset‑scrolling. All of which opens up all sorts of possibilities in the studio and on stage.

Hardware

Extending a shade over 250mm behind the rack ears, the XP‑Relay is pretty large for a 1U 19‑inch rackmount device. The review unit was configured for 16x16 mono channels, and the other available options are mono 8x8, stereo 8x8 and mono 16x8 — and I’m told that after‑sale reconfigurations are possible, which is nice. The internal PSU accepts mains AC power through a rear‑panel IEC inlet and, being a linear rather than switch‑mode supply, there’s a rotational switch to select the AC voltage (115/230 V, 50‑60 Hz). You need a screwdriver to change this, which I regard as a sensible precaution.

The XP‑Relay can communicate with its Mac/Windows control app over USB or Ethernet, and the latter allows connection to a router for, among other things, wireless MIDI control from a tablet or smartphone app such as TouchOSC.

Also on the rear panel are the balanced analogue inputs and outputs, in the form of four DB25 D‑sub connectors wired to the usual AES/Tascam standard. Alongside these are a USB B‑type connector, a five‑pin MIDI in DIN socket and an RJ45 socket. The XP‑Relay can communicate with the XPatch app via USB or Ethernet — the latter allows a directly connected computer to be placed further from the XP‑Relay, or, optionally, to connect the XP‑Relay up to a WiFi‑equipped router to allow wireless connection to a computer or tablet/smartphone running a third‑party MIDI control app.

The front panel is decked out in CB’s usual blue‑on‑bare‑metal livery, and the controls and connections that it hosts are equally minimalist. On the left, a pair of XLR sockets duplicate inputs 1+2 on the rear. Working in from the right, a quarter‑inch footswitch jack socket is followed by a knurled‑metal push‑turn encoder, a small but crisp colour OLED screen, and a power/data‑present LED. In the middle, eight low‑profile black buttons are arranged in a row, with an indicator LED above each one, hinting at functionality not present on the XPatches.

The XLR inputs will obviously be handy for musicians or engineers wanting to patch in different mics or line‑level instruments quickly, but unlike the XPatches the XP‑Relay has no outputs on the front. To some extent that’s understandable, given the lower number of channels, the larger components and additional facilities inside, but it means it’s not possible for, say, a mastering engineer or SOS reviewer to audition a new device without accessing the D‑sub looms you’ve previously plumbed into the rear of the device and your existing gear; maybe this is something CB could consider addressing in a future MkII version.

The eight buttons were originally conceived to allow phantom power to be switched on from the hardware, hence the +48V label above the LEDs. Phantom can be switched on/off individually for any channel, and to do this on the hardware you use the main encoder to select phantom (the default option on startup) and scroll to the desired bank of inputs (1‑8, 9‑16 or the two front‑panel XLRs), then hold down the relevant channel button while pressing the encoder. You can also operate phantom from the control app. Phantom power provision is welcome and convenient, especially if, as I do, you have some nice vintage preamps that don’t supply it, or have multi‑channel devices where it’s switchable only in banks. The presence of the encoder, though, means there’s scope to give these buttons secondary (or multiple) functions. During my review tests, I was in frequent communication with Colin Broad (the CB behind the company name) and suggested that they might be used to select routing presets — apparently I wasn’t the first person to mention this (great minds...) and within a day or two he’d already implemented it! How’s that for responsiveness?

Softly Does It

The XPatch app is standalone software, by which I mean there’s no dedicated DAW plug‑in version. At least not yet; I gather CB are looking to secure the services of a plug‑in developer. In the meantime, if recall from a DAW project is particularly important to you, CB were, at the time of writing, about to release an interim solution using MIDI SysEx messages. The XPatch app is accompanied by another utility called MIDI UPD, which is used for setting up the MIDI channels for any attached XP‑Relay and/or XPatch devices, and for installing firmware updates.

The XPatch app's Equipment page, where you specify what gear is connected to what inputs/outputs.

The general approach and layout of the XPatch software is broadly the same as when I reviewed the XPatch 32, but it has evolved considerably. There are four main pages and to start, having hooked your gear up to the XP‑Relay, switched on the latter and initiated the software, you go to the Equipment tab and define what hardware is attached to what I/O channels. You can specify whether the equipment is to be treated as a Source (something connected to an XP‑Relay input only, not an output — a mic, instrument or audio interface output, for example), a Destination (something connected to an output only, for example a compressor’s side‑chain input or active speakers), or a Device, which you’ve connected to both an input and an output (eg. a reverb unit or dynamics processor). This classification dictates how the gear is listed in the Paths and Matrix windows discussed below. In the Equipment page, you assign the XP‑Relay channel numbers to your equipment, along with a short name that will appear on other pages and the hardware, and, optionally, a few other details. It’s all pretty intuitive, though if you have only the XP‑Relay, you’ll find, alongside many useful facilities, some superfluous ones that apply only to the XPatch hardware, which could be confusing for new users.

The Matrix page of the XPatch software, which allows you to directly route from any input to any output — each source can feed multiple destinations.

With your equipment suitably specified, you can perform basic routing very easily from the Matrix page, which is laid out as a grid with Sources listed on the left and Destinations along the top. You simply click a square to link any source to any destination. A reassuring relay click, along with the a green dot in the square you clicked, confirm that the desired connection has been made. Another little detail added after speaking with Colin is that, as of v4.4, you can right‑click on a square in the Matrix page’s phantom power column to activate/deactivate phantom power for that Source.

The real power of this software, though, lies in the Paths page. Again, this is laid out in a grid‑like fashion, with lines and triangles to indicate the signal routing. You can create up to 128 routing presets called Paths in each of the many banks (an arrangement that will be familiar to anyone who’s worked with MIDI instruments and effects before), and click on them to (de)activate them. It’s possible to feed multiple paths from a single Source, and as long as two Paths don’t employ the same Devices or Destinations they can be active simultaneously. Activating a Path that shares a Destination with an already active Path deactivates the earlier routing. Also, note that you can use a Device as a Source, the idea being that you might want to use some gear, such as a mic preamp, as an input Source or as an insert Device in different scenarios. Creating Paths is much easier than last time I used this software, when I found I needed to rely more on my computer keyboard. Now, you can just click on either the Pallet button at the top or any empty insert ‘block’, and the Paths Pallet floating window appears. From here, you can drag any Source, Device or Destination to the desired position on any Path.

Each Path connects the equipment in series, with the signal flow running left to right. For mono Paths, there’s a dedicated downward triangle at each stage — click this and it mults the signal to the row below, making the creation of parallel processing chains really easy. At present, it seems that you have to (de)activate each parallel Path separately, but I gather CB are considering a grouping facility that would allow the whole parallel chain to be (de)activated with a single click/command. Stereo‑linked Paths don’t have the mult button (which I suppose could look confusing!), but similar routing is easy to achieve by creating and activating multiple Paths fed from the same Source. By the way, any routing selections you make in the Paths view will be reflected in the Matrix view.

The Paths page allows you to create preset chains of gear, with those sharing the same Destination deactivated as another is activated.

Remote Control Options

The fourth of the app windows I mentioned is called Snapshots, and allows you to save/load complete routing and phantom power profiles from/to the hardware. It’s a less versatile system than the Paths and if you plan on operating it using the software something you might not bother with, but importantly you can load multiple Snapshots to the hardware and switch between them using the footswitch, MIDI or, since a recent firmware update, the front‑panel buttons. If the XP‑Relay is connected to a router, you can also control it from a phone or tablet, using the TouchOSC app for iOS or Android. So anyone who relies on a few ‘standard’ routing configurations can load them onto the hardware, and then do all their switching without ever needing to attach a computer or open the app — and that obviously opens up many possibilities for performers.

Another convenient control option is to use an Elgato Stream Deck (see box) to switch different Paths on/off. It needs to be attached to a computer running the XPatch software to work, but means you never need to leave your DAW to look at the app, which is refreshing.

That the device can be configured using MIDI also opens up lots of options. For example, one user has set up an inventive MIDI‑controlled XP‑Relay system in which he places Bluetooth Flic Buttons (which can transmit MIDI) alongside his various instruments, and he can simply sit at an instrument, hit the Flic Button to enable the ‘normal’ routing for the instrument, and start playing. It seems more MIDI command options are being added too — for example, CB Electronics recently implemented commands to Disconnect Destination 1, Connect Destination 1 to Source 1, Connect Destination 2 to Source 1... and so on. For anyone with ambitions to get into the nerdy details, this system is brimming with potential for custom control setups.

Verdict

I was impressed with the XPatch but, if anything, I’m even more impressed with the XP‑Relay — it’s a winning combination of sophisticated software and refreshingly simple hardware. While the passive signal path means it lacks some XPatch functionality, it also opens up really useful options, such as comparing different mic and preamp combinations, without any of the compromises involved in doing that with the XPatches or, say, Flock Audio’s Patch. The XPatch app is much improved too, and the remote control options are evolving really nicely, not least the Stream Deck support — operating it from that has been a joy. I’ll be interested to see what comes of CB’s experiments with DAW integration too. There aren’t really enough inputs and outputs on this unit to accommodate my own mixing hardware setup, though two 16x16s could come close and there will be plenty of I/O for many — and there’s the option to use this device alongside an XPatch (or three!). Used on its own, the XP‑Relay would a great option for a lot of engineers, musicians and performers, whether on stage or in the studio, and it could be superb in an analogue or hybrid mastering setup. The price isn’t bad considering what’s on offer, either — so if an automated analogue patchbay holds appeal, the XP‑Relay has to be worth auditioning!