Making Audio PatchPanels

I had always admired the thinking behind the use of patchpin panels instead of standard 6.35mm patch cords on the EMS synthi A and VCS3. Even today panels like these are really useful in constructing compact modular synths or other projects where patching needs to be done. Patchpins offer convenience and ease of use which perhaps in the case of the synth A/VCS3 is a factor that gives these machines a kind of mesmeric appeal. They also mean a fantastic array of possible connections between your modules.

The problem with purchasing audio `matrices’ similar to those found on the synthi is that they are very expensive. Ghielmetti is a company that produces them and indeed I believe Juergen Haible used one in his splendid Synthi A clone. The alternative to purchasing one might be to try and build one! Well, I don’t mean to the specifications of those produced by Ghielemetti (or Sealectro for that matter),but one that would use readily available sockets and jack plugs. Obviously one requires the smallest (2-pole) sockets available if a reasonable panel like 20 x 20 isn’t to be overly large. I decided to experiment with 2.5m sockets. Quickly you realise that the cost of 400 such sockets may still be steep! I was lucky in that I found that cpc in the UK was selling 2.5mm low profile sockets(see pic below) for the dirt cheap price of a few pence each! But even paying something like 10p each would still mean that a 20x20 panel would be within reasonable cost. Although I didn’t investigate, it could well be that if you find an OEM of low profile sockets, buying in bulk (which you have to do anyway)could still make the project cost effective.

The sockets I used (Fig 1.) had a square profile of 5mm x 5mm. With the position of the solder tags, the smallest spaced lattice I could arrange them on was 8mm x 8mm. For a 20 x 20 panel, that meant something approach 170 cm square which although larger than commercial panels is still reasonably small.To build the panel I decided to use aluminium plate (2.5mm) on which I would drill the lattice of holes. The hole diammeter was such that each socket was a very snug fit. With a dab of superglue I was happy that they were very secure.

Equally a laminate like traffolyte (as used in Sealectro panels) could have been used and is easier to drill. To get an accurate drill template, its best to produce the array of drill holes using Front Panel Designer, and then glue the printed artwork onto the aluminium plate. The first few panels I made were drilled by hand..but then I got a drill press, which makes the job far easier and quicker. You can easily make a drilling jig which allows accurate alignment of the drill head with the artwork. I used this method later when I had to make a front plate for a sealectro panel (see sealectro ).

Once you have the drilled panel you simply have to insert all the sockets.However due to the position of the solder tags in the sockets I used, its not possible to first insert all the sockets and then wire up the rows and columns.I had to basically insert a row, then solder a tinned copper wire to each row tag on the sockets,and then continue to add rows of sockets and wires untill you have inserted them all. Then you solder the wires that make up the columns.

It sounds complicated but its not..just boring! If you take your time, you can make a 20 x 20 matrix like this over a weekend. Fig2 below shows the rear of a panel I made. You can see the tinned copper wires that make up the rows and columns. I used reasonably thick tinned wire, so that the resulting lattice of wires is very strong.

In the first panel I made, the sockets were so secure I didn’t need to add a backing plate in order to support the whole lattice of sockets to the pressure of pin insertion. In later panels I skipped the superglue (it speeds up construction) and added the backing plate. Either method seems ok. In Figs 3 and 4 you can see that the sockets protrude slightly in front of the panel.

Figure 1: lots and lots of low profile 2.5mm sockets....

Figure 2: rear view of the panel, showing the row and column wires

Figure 3: view of front panel. The sockets slightly protrude from the panel

So far I have constructed 3 panels in this way which are used in my modular Synthesizer. They basically function AS SIGNAL, CONTROL and OUTPUT routers. Click the links below to see screen dumps from Front Panel Designer (quality is reduced from the original I’m afraid)

SIGNAL MATRIX CONTROL MATRIX Output Matrix

A page explaining how I modified 2.5mm jackplugs to obtain `patchpins’ for the

Above panels can be found here patchpins