Studio wiring and patch bays, there’s a lot to think about. In this article, Mike shares his studio wiring system, including making wiring, and more importantly rewiring, patchbays and the studio as a whole, much easier to manage. The key is insulation displacement blocks, made by a number of manufacturers including Krone.

Some Background

As some of you will know I came into the pro-audio sector from an engineering background, more specifically electronic engineering. It’s in the blood, my dad was an electrical engineer. Think of those pylons striding across the countryside, that was his area of expertise. But not just above ground, also under the sea. For example, he oversaw the first submarine power cable laid between North and South Island in New Zealand. His other passion was hi-fi, making from scratch,his own speakers, amps etc, back in the days when valves were the only way, transistors hadn’t really happened yet.

After my apprenticeship at Marconi’s, the home of radio, I spent nearly 10 years in the 1980s as an engineer at Piccadilly Radio in Manchester, England, responsible for keeping the station on the air from a technical perspective as well as undertaking all the improvements, upgrades etc.

Let’s just pause the story and explain what studio wiring and patchbays are all about.

What Is Studio Wiring?

Studio wiring, at its simplest, is routing one cable from point A to point B. Now that could be from two pieces of equipment next to each other or in two different rooms within a building. You can use multicore cables when you have a number of cables following the same path, but ultimately at one end it is likely that these pairs will need to go to very different places. Even so, at the installation stage that can all be planned for and accommodated.

What Is A Patchbay?

At its most basic, a patchbay brings the connections from the back panels of all your gear (whether that is outboard equipment, like compressors, EQ, and reverb units or your mixing console) onto a panel. You can then use patch cables or cords to link units together, as we want them, without the need to fumble around the back of the racks to connect the gear, keeping it all nice and tidy.

Even though installing a patchbay in a studio adds complexity to the studio wiring, it is worth it to make the studio easier to use. One minute we could be tracking using a compressor as an insert on an input channel and the next we could be using the same compressor on our master bus. Changing this configuration by messing around the back of racks, is at best a pain in the ^%$£!, whereas using a patch panel or patchbay, or a jackfield, as I prefer to call them, makes changing our routing nice and simple, and nice and tidy.

There are a few patch bay basics you need to understand before we dive into specifics. Most patchbays position outputs and inputs in dual rows housed in single rack unit modules. This is so designers can piece together bays of any size by adding modules as they are needed. 

1. What is normaling? It's a connection made from an upper row to a lower row without having to make a patch. For example, a console's direct outputs, or bus outputs normally feed the DAW's inputs. It would be silly to have to make each one of these patches so they are married together via a patch bay using normaling or sometimes called a normal and sometimes mistakenly called normalising.

2. How does a normal work? A ‘normal’ is when a signal from an output row (the top row in a patchbay) automatically feeds the input row below. The connections on normals are made on the backside of the patch bay, the part that's invisible to the user. There are two kinds of normals, full and half.

   1. A ‘half-normal’ means that when you choose to patch from a normaled output row, it does NOT break the signal as it flows to the input row below.

   2. A ‘full-normal’ does the opposite, should you choose to patch from a normaled output row; it DOES break the signal flowing to the input row below.

3. What is a mult? A mult, called a parallel in the UK, is a passive splitter meaning it will duplicate a single input to multiple outputs. It should never be used to sum two or more signals together. It is most often used to split a single output so you can send it to multiple inputs. If you are splitting a stereo signal you need to use two parallel. A parallel should only be used for line-level signals and should never be used for mic or speaker level signals.

A well-planned patchbay should have no cables in it. It should be configured so that all the regular connections are made within the patchbay. This means that you only need to use patch cords to ‘over-patch’ something when you need to configure something differently.

Need To Makes Changes?

At Piccadilly Radio we were always researching new techniques, and we came across Krone blocks. They are used mainly in telephone communications but we realised, like some other products aimed at the telecommunication industry, that this technology could also be applied to pro-audio.

Spool forward a couple of years to when we needed to make changes to accommodate new or different equipment or to accommodate changing workflows, making changes to the wiring and patchbays became very complicated, with cables now needing to go to completely different locations, often requiring the opening up of looms, some cables extending, whilst others shortening and it is very difficult to keep the whole thing tidy.

What Are Krone Blocks?

Krone Blocks are, at their simplest, a block that can take 10 balanced pairs. Add to that, cables that have 10 twisted pairs with an overall screen and jacket, and very quickly you can have a system built around 10 pairs going to key locations and then individual wires going from block to XLRs, Jack Plugs etc to hook up equipment.

But that left the challenge of patchbays and jackfields. The brainwave we had, was to wire the jackfield up just once using this 10 pair cable, which here in the UK is called PSN20 and then terminate them onto Krone blocks.

This meant that we never needed to open up patchbay looms. They were effectively pre-wired. We even developed a system that meant we could configure the normalling on Krone Blocks with ‘jumpers’. All of which meant when changes needed to be made, we did not have to rewire the jackfields.

Designing My New Studio

Roll forward another 10 years, to us moving house and me having the opportunity to build a new studio from scratch back in 2001. I decided that I would adopt the Krone System that we had developed at Piccadilly Radio 15 years earlier. My previous studio, in the old house, had gone through a number of reconfigurations as needs changed and equipment came and went, and by the end, the wiring was not the tidy looms I had started with. With the new studio, I was determined to use Krone Blocks and PSN 20.

In the main rack bay, I created a 40 block frame for the Krone blocks (shown on the right). In the end, I chose not to do the normalling on the Krone Blocks as I was already at nearly 20 blocks for my jackfield and the normalling technique would have added at least another 10 blocks.

The other 20 blocks on the frame are made up of 6 blocks going to another rack, 2 blocks going to the computer cupboard, 4 blocks going to the equipment built into my desk, all wired using PSN20 to satellite frames in the different locations.

Then all I needed to do was run short tails from the satellite frames to each piece of equipment.

As there was quite a bit of equipment going on the main rack, the rest of the 40 block frame was for the tails serving as satellite blocks for the gear in the main rack.

To hook it all up it was simply a matter of running ‘jumpers’ from the appropriate pair on a Krone Block to the correct pair on the jackfield looms.

Insulation Displacement Technology

There is no need to strip ends and solder, the great thing about insulation displacement technology as you lay the wire in the slot and the Krone tool then pushes the wire into the block where blades cut through the wire’s insulation and make contact, and then the tool’s scissors cut off the excess all in one action. Quick and efficient, and very easy to make changes.

The Pro Tools MTRX Studio has much more I/O than the HD Omni and the HD I/O interfaces and so the jackfield would need a major reconfiguration but with my amazing system that wasn’t going to be difficult.

This meant that the four PSN20 multicores going from my desk to the rack would need reallocating and 2 more runs added to accommodate the increased I/O and the feeds to the Dolby Atmos speakers.

Good Records Are Essential

When I designed the studio, I also decided that the cabling records would be computerised rather than being old fashioned paperwork. To that end, I created a spreadsheet to document the function of each pair on each one of the 40 Krone Blocks (see above). This also recorded the function of each pair of the satellite frames in the second equipment rack, the computer cupboard and the desk.

I documented the jackfield layout in a second spreadsheet as well as creating the ‘desig’ strips labelling the function of each socket on the jackfield using a template so all the words would line up with the sockets on the jackfield.

As a result of various adjustments over the 20 years, when I arrived at the current update, the paperwork was already on V3. I did a ‘Save As’, labelled it V4 and completed the reallocation on ‘paper’, tweaking it until I was satisfied.

I also produced a list of tasks (some of which you can see on the right) including which jumpers would need removing, which jumpers would need re-routing and which needed new jumpers altogether on the master Krone frame.

With the additions required to service the MTRX Studio, the jackfield would need a major reconfiguration, which would be so much easier with the Krone based wiring system. In the images above you can see the changes between V3 (old) and V4 (new).

I also needed to change the desk satellite Krone frame from a 4 block frame to an 8 block frame. I then used the redundant 4 block frame to accommodate the blocks for the two new PSN20 cable runs under the master Krone frame. You can see the differences between the old jackfield layout (V3) and the new layout (V4) above.

Before I could add the new cables there were quite a few redundant cables to remove. Also, I wanted to do away with the ‘rats nest’ of cables and leads that had built up over the years under the desk as a result of various smaller upgrades and temporary modifications, that became permanent.

Once everything was planned, and I had booked a clear 2 weeks to be without a lot of the studio features, I started the rewire, first emptying the main rack to give me access to the master Krone frame

I opened up the cable ducts again and spent a day clearing out the redundant cables. Then I started wiring from the furthest point, reconfiguring the desk I/O panel to provide XLRs for the MTRX Studio mic inputs, because unlike the HD Omni mic inputs they were on the rear panel on the MTRX Studio.

Also, I added 2 XLRs for the mic inputs of my two PreSonus RC 500 channel strips, which I use when recording screen capture videos to replace the flying cables that were a temporary/permanent solution when I bought the PreSonus units. 2 inputs for the ‘Gram’ (a Technics SP10 turntable which I keep stored away and only bring out when needed), 2 inputs for my Laptop audio output and then 4 headphone sockets from my ‘cans’ amp situated in my second rack. These are additions to replace temporary/permanent headphone extensions because the headphone sockets weren’t in the right place.

Next came the wiring in of the MTRX Studio and cabling ready for an ADAT to line-level audio unit, yet to be purchased. In all that was six 25 way D-Sub connectors. I was planning to use D-Sub looms but then I had a brainwave. What if I bought 25 D-sub to D-sub cables, the ones you used to use for printers or SCSI leads, long enough to cut in two? I could wire these to the Krone blocks as the cable would be very similar to the PSN20 I was using, with the bonus that they would be much cheaper than the D-sub looms.

I had to ‘bell-out one of the cables to identify which coloured wires went to which pins on the D-sub, but once that was done it was so much easier to wire up the six D-sub cables, 4 for the 16 ways of line-level audio in and out of the MTRX Studio and two, ready for an 8 way ADAT extender.

You can see them in the image on the right. They are the multi-coloured wires on the bottom of blocks D1 and D5 and they are on the top of blocks D7 and D8.

In case you are wondering about the red block at the bottom is an earth block, and for some reason, they come in red!

Once the 8 block subframe was completed, I could then continue to make the necessary changes in the second rack. Then it was time to rewire the master frame. Working down my pre-planned list, I first removed all the redundant jumpers, then re-routed the ones that needed re-routing and finally added all the new ones.

Testing, Testing, 1-2-3

No one is perfect, least of all me and because the master Krone frame would be hidden once the equipment was refitted in the main rack, I set about testing everything, not just the changes I made, before I installed the amps for the speakers and the other units.

It was an ideal opportunity to make sure that everything worked as expected. I had already checked the equipment that was going back in like the cassette deck and DAT machine, to make sure I wasn’t putting back duff gear!

This process threw up a few issues, 4 wiring errors and 2 faulty units. When I built this studio in 2001, we had just bought this house and had to spend a lot on new furniture, carpets and a new kitchen so cash was limited and so I went for a Behringer line-level mixer and cans amp. I knew that parts of the cans amp were unreliable and I wasn’t too sure about the line-level mixer either.

The tests confirmed that the cans amp was faulty, but the good news was that I had a Samson unit in a flight case from when I was doing a lot of location recordings, so that was a simple swap. The mixer also proved faulty with an imbalance in the signal level between the left and right outputs. So that will need replacing and it will probably be replaced with a Samson SM10.

What’s Next?

That is about it. I am still configuring the MTRX Studio but that process will be the basis of at least one future article just to cover the setup and configuration.

Then there is the installation of the Dolby Atmos speakers. For those of you who have been following my upgrade story, I chose to buy more secondhand PMC speakers to match my existing 5.1 system. The next task will be installing four PMC DB1s in the ceiling and adding a pair of TB1s as the side surrounds, which together with my three LB1s across the front will make my 7.1.4 Dolby Atmos system, but that too will be the subject of another article.