PART 5: Nothing dampens creativity more than a studio full of 'spaghetti' cabling. This month, Paul White explains the virtues of installing a patchbay to banish cable clutter once and for all. This is the last article in a five‑part series.
Last month I introduced the essential features of a multitrack mixer and described how it acted as a central routing system for the studio. Even so, there are still some routing tasks that can't be achieved using the mixer controls, so to accommodate these we need to add one or more patchbays to the system.
Patchbays come in two basic configurations: normalised and non‑normalised. Normalised patchbays contain switch contacts, so that the signal flow is unbroken when nothing is plugged into the patchbay sockets. Non‑normalised patchbays, on the other hand, can be considered as the audio equivalent of extension leads, allowing you to bring existing connections out to a more convenient location. Professional studios generally use patchbays which have miniature 'bantam' jack connectors, but in the project studio where we need to interface with a wide range of musical instruments and processors — most of which employ standard quarter‑inch jacks — a quarter‑inch jack patchbay makes a lot more sense. It's also a lot cheaper than using bantams. Jack patchbays come in unbalanced and balanced versions, using mono and stereo jacks respectively, and in most instances connection to the rear of the patchbay is again achieved using jacks. For a full description of patchbays and their workings, see 'Practical Studio Wiring II' [SOS May 1994].
Even if you have a very small recording system, patchbays can still help you operate more smoothly by bringing things like insert points, effects sends and returns, and the inputs to your various effects and processors to a convenient, central point. There are few things that dampen the creativity more than having to start pulling plugs out of the backs of units. However, providing the jack sockets on your mixer are reasonably accessible, there's no reason to use a patchbay for connections that are rarely, if ever, changed.
Note that the convention for patchbay wiring requires that the bottom socket of a pair should be the input, and the top socket the output. Because some commercial patchbays are provided semi‑normalised (ie. the signal patch is only broken when you plug into the bottom socket), using them the other way up will prevent them from working on those occasions where you just want to take a feed from the insert send without breaking the signal path. Again, this concept is explained fully in the previous article on patching, so I won't go into too much detail here.
Technically speaking, the signal path is cleaner without a patchbay because there are fewer resistive contacts for the signal to pass through (every plug and socket represents a resistive contact), so if you can organise your system to keep patching to a minimum, not only will you save money but you'll also reduce the risk of signal degradation. The secret to getting all this right, of course, is planning. An evening or two spent with a notepad and a pencil is time well spent, and the bigger your studio setup, the more important it becomes that your patching system is designed properly.
If your setup is large, consider using foil‑screened cable or some other suitable small diameter screened cable for patchbay wiring, otherwise you might find the wiring harness ends up being incredibly bulky. If you're not sure which cable is best for a specific application, try to get a copy of the Studio Spares catalogue [Tel: 0171 482 1692], as this carries a variety of cable types and describes their applications. For smaller systems, regular screened instrument or mic cables (or even ready‑made moulded jack cables) will suffice.
Let's take the obvious things first: you can't really pre‑wire processors such as compressors or gates, because you don't know what mixer channel they'll be needed in (unless you use your studio purely for your own work and always work in exactly the same way). Consequently, most studio patching systems bring out all the mixer's Channel, Group and master Stereo insert points to a patchbay. The majority of project studio mixers use unbalanced insert points, where a stereo jack carries both the send and return signal, so you'll need a mono, normalised patchbay and a whole bunch of Y cables (cables with a stereo jack at one end and two mono jacks at the other). Again, the SOS article on patchbays describes Y cables in more detail, but in any event, this kind of information is usually provided in your mixer's handbook. If you can face the prospect of soldering, it's far cheaper to make your own Y cables, though companies like Hosa do offer ready‑made Y leads that are fine for use in smaller systems.
There are few things that dampen the creativity more than having to start pulling plugs out of the backs of units.
Having connected up the insert points, it's also useful to bring out both your auxiliary sends and returns, plus your various effects and processor in/outs (not forgetting any side‑chain access points). If you have a mixing console with plenty of aux sends and you only own two effects units, it may make sense to wire these in permanently, but it's still worth bringing the remaining sends out to a non‑normalised patchbay for the occasions when a friend brings over another processor which you want to use.
Most studios use at least two types of stereo machine, often a DAT and a cassette deck, and if you do any kind of commercial work you may also have an open‑reel analogue mastering machine. If your mixer doesn't cater for multiple mastering machines, then the various machines and the mixer stereo output will have to come out to patch points, so that you can connect them as required. In my own system, I've used a normalised patching system so that when nothing is plugged into the patchbay, the mixer output feeds into all three tape machines at once. However, when a plug is connected to the input of one of the machines, it is isolated from the mixer output. This way I can mix directly onto any of the three stereo recorders (or all at once if I wish), but it's also easy to patch the output of one machine back to the input of another for copying. Similarly, the output of any tape machine can be patched into a mixer input if you wish to add taped sounds to a mix.
While it is quite possible to plug things directly into the input sockets on your mixer, you'll probably find it more convenient to bring the input channels out to a non‑normalised patchbay. If you want to use your mixer's Direct channel outputs (if you have them), you can use a single patchbay with the Line inputs on the bottom row and the Direct outputs on the top. If you don't have Direct outputs or don't need to use them, then you can use both rows of the patchbay as inputs rather than adhering rigidly to convention.
At this stage, it's also worth looking at the audio outs from your MIDI instruments (synths, drum machines, etc). If these are normally connected to specific mixer channels, you might find a normalised patchbay is a good idea as this would allow you to break in and take a synth output or use a mixer input without having to unplug anything. Having said that, if you're confident that you will hardly ever need to change the way things are patched, there's a lot to be said for not having a patchbay there at all.
On the MIDI side, if you have a lot of sound modules, or if you're in the habit of working with more than one type of sequencer, a simple, mechanical MIDI patchbay comes in very handy. These are simply front panels fitted with DIN connectors, and there are usually more DIN connectors on the back so they can be wired up using standard MIDI leads. Even if you don't need one of these to handle the MIDI feeds to your instruments, it makes life easier to use one for the MIDI Outs as this makes it easy to patch a synth back into your computer for editing. Programmable MIDI patchbays may seem to offer a more sophisticated solution, but we hear so many horror stories about them not passing System Exclusive messages properly that I would be inclined to keep things simple and put up with moving the occasional patch cable.
In a mainly MIDI studio with only one or two microphones, it's hardly worth putting in any special provision for them — you might just as well plug them straight into the mixer whenever you need them. In the larger studio though, or one with a separate playing area, then it pays to run a balanced multicore cable from the mixer's Mic inputs to a wallbox fitted with balanced XLR sockets. The multicore should comprise individually screened balanced pairs and should be kept away from mains cables, if at all possible.
I don't think the perfect patching system exists, but by thinking about what you want to achieve, you can come up with a system that will allow you easy access to all the most frequently changed signal paths. Modern patchbays can be switched from normalised to non‑normalised operation, usually by soldering a wire link or by reversing a circuit board. It's therefore no problem to configure a patchbay that has, for example, 16 pairs of normalised sockets for insert points plus a further eight pairs of non‑normalised sockets to handle your effects unit inputs and outputs. OK, so patchbays cost money and they take time to wire up, but they work out a lot cheaper than the hair transplant you might end up needing if you don't have a sensible patching system!
Normalised patchbays are used in situations where a signal path needs to be interrupted, in order to either insert another audio processor into the signal chain or to divert an input or output somewhere else. Insert points must always be normalised, but normalised patchbays are also useful for connecting your multitrack inputs and outputs to the mixer — they allow you the flexibility of patching in a different multitrack machine or routing things like mic preamps directly to tape without going via the mixer.
Inputs and outputs to effects processors should be connected to a non‑normalised patchbay, unless you want to set up a default system so that certain effects units are routed back to certain mixer channels or effects returns. It's a good idea to plan your patchbay so that when no patch cables are inserted, you have a default setup which allows you to do all your basic jobs without having to plug in any patch cables at all. That way, you only have to patch when you want to insert a processor or do something a little out of the ordinary.
Clear patchbay labelling is important, but with the small size of today's 1U patchbays, this isn't always easy to achieve. P&R Audio's patchbays, for instance, come with a sheet of self‑adhesive labels, some blanks, but most printed with commonly used terms such as 'insert' or 'input', and numbered up to 24. These certainly help, but when it comes to your effects units or synths, you still have to make your own labels. After much Blue Peter style experimentation, I've come up with a system to make my own self‑adhesive labels — it involves both double‑sided tape and Scotch tape, but sticky‑backed plastic is optional.
I find it's tidier to make the labels in strips of eight channels, rather than trying to line up individual labels over individual sockets. The reason I go for eight is that you can easily print one across a sheet of A4 paper. The other reason is that with a 24‑way patchbay, you only need three to go right across. Using any word processor, set up the tabs to match the spacing of your sockets. The ruler facility built into most word processors will help here, but you may still have to print a few test pieces to get the spacing exactly right. Use a small, clear typeface (Helvetica or Geneva is good), and if you have the facility to condense the type, you'll probably be able to fit in most words without using too many abbreviations. Setting the type to 'bold' may also make it easier to read.
Having done this, type out your patch labels using double spacing between rows. If possible, use different colour paper for inputs, inserts, and so forth, to make everything visually clear. Any cheap inkjet printer will do a good job of this type of work, but if you have access to a laser printer, so much the better. Even if you don't have a computer, you'll probably be able to get a local typing bureau to do the job for you relatively cheaply (see your local Yellow Pages under 'typesetters').
Stage two involves sticking double‑sided carpet tape on the back of your labels, and clear Scotch tape (the matt stuff looks best) over the front to protect the printing. Finally, use either a guillotine or a steel ruler and Stanley knife (or scalpel) to cut the labels into strips about a quarter of an inch wide.
Now all that remains to be done is to peel off the protective backing and stick your labels onto your patchbays. Old adhesive left over from previous attempts can usually be removed by spraying it with household spray polish and then leaving it for a few minutes to soften. But don't get spray polish down the inside of your patch sockets!
Even a relatively small studio can become a wiring nightmare if you don't keep track of what's going where, so it's a good idea to label all your leads and plugs as you go along; sticky paper labels protected by Scotch tape are usually adequate. It's also vitally important to have clear access to the back of your patchbays, as I discovered to my cost when I built a system that could only be accessed by removing the patchbays from the front! The combined weight of several wiring harnesses is not inconsiderable, so if you try to pull out a patchbay from the front, the chances are that all the jacks plugged into the back of it will pop out.
It may also help to use a larger than necessary racking system for your patchbays, so that you have somewhere to coil up the extra cable that somehow seems to accumulate. In a perfect world, all cable harnesses would be exactly the right length, but it can help to make them a few feet longer than necessary to provide a little flexibility for when you next change your studio layout.
Because most patchbay connections run to the mixer, it makes sense to keep the patchbay as close to the mixer as possible, but you also have to consider the placement of your effects rack because all your effects ins and outs also end up at the patchbay. In my own studio, I've built a combined patchbay and effects pod that sits right alongside the mixer, so that only the MIDI rack and multitrack/DAT wiring harnesses are visible. In theory, shorter cable runs will reduce the risk of interference and crosstalk, but equally important is the fact that less cable costs less money!