Isotrack Smartpatch

As an exercise in lateral thinking, re‑patching your studio is a delight. As an actual prospect, it's somewhat more daunting. Paul White plugs into a programmable patchbay and lets his fingers do the walking...

The concept of programmable patchbays has been around for a while, but somehow they never quite made it into mainstream recording. My own view is that the early models were too expensive, too complicated, and if anything, they arrived on the scene about five years before anyone realised they needed them. Now that we are all familiar with the broader concepts of MIDI, MIDI muting and MIDI console automation, programmable or MIDI‑controlled signal routers seem far less esoteric.

Based in Dorset, Isotrack have been around for as long as I can remember, their main stock in trade being very nicely engineered patchbays priced to appeal to the home recording market. More recently, they have moved into the pro‑Bantam patchbay market with considerable success, but the Smartpatch heralds a completely new product area for the company.

Essentially, the Smartpatch is a 16‑in, 16‑out audio patchbay available in both balanced and unbalanced configurations, but instead of requiring physical patch cords, the necessary connections are provided by an internal switching matrix controlled by two rows of front‑panel buttons. Each input and output has its own button and its own status LED, and any input can be routed to any output, with the proviso that only one source can feed one destination and vice versa.

Once the patchbay has been set up, the resulting Patch (in this case, a term for a snapshot of all 16 input and output patch settings) may be saved for later recall, and up to 128 different Patches may be stored. Patches may then be recalled via the front panel buttons or via MIDI Program Change messages, though there's also provision to send real time patching data out over MIDI, so that it can be stored in a sequencer for more ambitious applications.

Frankly, I think that having 128 snapshot modes to work with is enough for most people, but because real‑time patching is available, it's possible to perform other tricks. The Smartpatch can be used as a MIDI muting system, for instance, by plugging it into the console insert points and then using MIDI messages to make and break the connections. Alternatively, the Smartpatch could be used to create simple MIDI gating effects.

On The Case

Physically, the Smartpatch is refreshingly straightforward — it's a 1U, mains‑powered box with all the audio connections on jacks at the rear, along with the MIDI In, Out, Thru and Power connectors. The patchbay section, comprising two rows of clearly labelled buttons, is set out over the rightmost two thirds of the front panel, with round buttons where you'd normally expect to see the jack sockets on a conventional patchbay. Each button has its own red LED, and when a Patch is loaded, you can see what is routed to where by pressing any input or output button, whereupon the LEDs pertaining to both source and destination buttons will light. If a connection is not routed, pressing the button will cause its own LED to light, but no other LED will come on.

In Edit mode, patches can be made and altered simply by holding down a button on one row and then pressing the desired target button in the other row. Similarly, if a connection is already made, holding down the source button while pressing the destination button (or vice versa) will break the connection and the LED will go out. The only time you can't edit a patch in this way is if you attempt to make one source feed two destinations, or vice versa.

A numeric LED display indicates the patch number in normal operational mode, and if a patch includes one or more connections, a decimal point appears on the far right. A simple procedure allows patches to be copied, but I couldn't find a button to allow me to reset all connections in a patch to off, which I thought might have been a good idea. As it is, you have to switch them off individually, or keep a blank patch somewhere that you can copy. It might also have been a good idea to fit a rear panel memory lock switch.

MIDI Control

Conventional Inc and Dec buttons are used to move up and down the patches, and the new patch information is loaded once the Patch button is pressed. Alternatively, MIDI Program Change messages may also be used if Program Change is switched on. This is accomplished by pressing the MIDI button to enter MIDI edit mode: here, you also set the MIDI channel being used, plus the data format in which real‑time patching information is sent.

Because some sequencers don't record and play back some control changes or poly pressure, the Smartpatch lets you choose from the three different types of MIDI message to represent real‑time patching: Poly Pressure, Pitch Bend or Control Change, and there's a choice of control change numbers available. Once in MIDI setup mode, the necessary selections may be made using the Inc/Dec buttons and the first few routing buttons on the bottom row — these are the only dual‑function keys in the system, and as they're only used in MIDI setup mode, there's little likelihood of confusion. However, on the early production model I received for review, only the first four buttons were labelled with their alternative functions, which meant I had to keep looking in the manual.

In MIDI mode, LED 12 on the bottom row flashes to show that MIDI data is being received, and you can also use MIDI to save the Smartpatch memory as a SysEx dump (either as single patches or the whole memory). A nice touch is that Isotrack have retained the labelling system from their existing patchbays, in which a thin cardboard strip is slid into a flat, transparent plastic sheath fixed to the patchbay.

Technically Speaking

The matrixing chips used in this patchbay don't present the zero resistance of a theoretically perfect plug and socket, but with typical audio signals, the nominal 150Ω on resistance is negligible, and in any event, far preferable to the wildly‑varying resistance of a contact that's started to become noisy. With a source signal of 600Ω and a load impedance of 10kΩ, both of which are in the right ballpark for most line level audio equipment, the frequency response of the switches is only 3dB down, at 20MHz — so even serious treble freaks have no worries on that score!

The maximum insertion loss is quoted as 0.02dB max (a technical term for bugger all!), and the signal handling capacity of +/‑ 12V leaves plenty of headroom for hot signals, although it's still a couple of dBs less than you might expect from a well‑designed mixer. I suspect this is a limitation of the switching chips, but unless you're in the habit of running everything at around +20dB, you needn't worry. The actual input impedance of the patchbay is around 100kΩ, which means normal line level signals won't be affected at all, and the system noise floor is better than ‑100dB.

I suspect that the switching chips are the same ones used in high‑quality telecommunications applications, which means the audio quality is excellent, but there is one factor of which you need to be aware. These systems switch very quickly, unlike most MIDI muting systems, which have soft switching deliberately built‑in. In practice, this means it's unwise to make or break any signal path that has a signal on it, otherwise you might hear clicks. This isn't a fault of the system — switching any audio signal on or off with mechanical switches has the same effect, but it does mean you have to plan your patch changes or real‑time routing operations carefully.

Because of the way the switching chips work, it isn't possible to cascade two patchbays to give you 32‑in, 32‑out capabilities, but you can use several Smartpatches independently, by allocating a different MIDI channel to each one.

Usability

The Smartpatch is simplicity itself to use — some of the programmable patchbays I've seen in the past have a learning curve that only the brave would tackle without crampons! With the Smartpatch, it just takes five minutes or so with the manual, and you're away. The audio quality seems fine: there's no noise, distortion or change in signal level that I could hear, and there's no switching noise, provided you don't change patches when there's a signal passing through them. Similarly, the level of crosstalk is too low to hear, the quoted figures being 92dB at 1kHz and 69dB at 20kHz.

With the Smartpatch, it just takes five minutes or so with the manual, and you're away.

As expected, switching while a signal is present does usually result in a small click, but if you switch on a drum beat, or use the Smartpatch to gate a signal in a rhythmic way, I don't think the click will bother you. However, if you use it as a conventional mute system, then you really do have to switch during a pause in the music.

The MIDI side of the unit checks out with no problems, though how easy it is to record and edit patch data in your sequencer depends largely on the type of sequencer you are using. Also, because two buttons have to be pressed to make or break a connection, programming patches on the fly requires a certain degree of dexterity, especially if you want to record a lot of moves within a short space of time.

Verdict

The Smartpatch is actually a very useful piece of kit, and it has the additional benefits of being sensibly‑priced and very simple to use. Any limitations are inherent in the switching chip used, the most serious being that you can't chain several units to expand the matrix size. On the MIDI control front, I felt that the designers could have included the more common MIDI Note and MIDI Velocity system of representing switching data, rather like you find in many MIDI muting systems. This has the advantage of being a little easier to edit from within a sequencer, though I have to be honest and say that most of the useful applications I can envisage for the Smartpatch don't rely on MIDI patch‑changing at all.

For me, the great attraction is being able to switch between several preset configurations at the touch of a button (or two), without ever having to bother about patch cords, dodgy sockets or faulty leads. Maybe not everyone will feel the need for a programmable, cordless patchbay right now, but let me disabuse you of the notion that it couldn't benefit you. As I recounted earlier, I think that with a modicum of planning, most users could really simplify their patching system and end up with a more reliable, more streamlined setup, without having to accept too many operational constraints. I don't think that the Smartpatch will ever completely replace conventional patching, nor is it intended to, but on the whole, I feel it's a well‑thought out product that will have more uses the more you think about it.