A DIY Audio Patchbay made from a Solderless Breadboard

2009-01-29 Robin Whittle  rw@firstpr.com.au 

To other things I made: ../   To the Devil Fish page: ../../rwi/dfish/ .

Minor update 2009-10-02: See Jeff Jonas' page http://ferretronix.com/stuff/breadboards/ on the history of these breadboards from a company which changed its name from Elenco Precision to Continental Specialties and then to Global Specialties.  These prototyping boards are such wonderful things.  See the directory here Continental-Specialties/ for some photos, including of a 1976 standalone unit, with powersupply, called the CSC Design Mate 1.

This is how I made a patchbay in the early 1980s for linking together tape recorders, drum machines, synthesizers, reverb units etc.  There was a discussion about how to make patchbays on the Synth DIY list (http://dropmix.xs4all.nl/mailman/listinfo/synth-diy) in late January 2009.

"Solderless Breadboard" or "Solderless Bread Board" seems to be the best term for these things now.  At the time I made this, the initial and perhaps only manufacturer was a US outfit called "Continental Specialties" and the strips were known as "QT Strip".  This was in the mid-70s - and Googling the term now turns up nothing.  Ahh - I see the company changed its name to "Global Specialties".  Googling this with "Proto-Board" turns up some products . . . yes - they are still in business: http://www.globalspecialties.com/proto_accessories.html .  Indeed the very same QT Strips I used are still available: http://www.globalspecialties.com/qt59s.html .

I haven't used this for years, since I am currently not set up for making music with a bunch of gear.  It has been in a box, and looks worse for wear:

Audio patch bay made with solderless breadboard

I removed some of the plastic insulation on the back.  Then I soldered to the back of the metal connectors.  Every second connector is ground.  This stops capacitive coupling from one signal to the next.  Soldering is tricky, since it was easy to melt the plastic.  I may have run a file or some abrasive paper down the area I was going to solder, to make it easier to solder.  (Don't try this with leadless solder - it is too hot and does not wet as nicely as real solder.)

For a description of what is inside these protoboards: http://www.ece.rice.edu/~jdw/242/breadboard.html

Every other connector on the left was an input of some device and on the right I had the outputs of some device, usually the same as whatever was on the left.

I soldered the shielded wires directly to the back of the QT strip.  The shielded wires went out to the appropriate connector for the device.  So it was the centre of the studio, with cables branching out all over the place.

Audio patch bay made with solderless breadboard

Audio patch bay made with solderless breadboard

Audio patch bay made with solderless breadboard

Connections to patch things together were simply made with single strand "bell wire".  It is also possible to get fancy connector leads with flexible wire:


There was no shielding of the actual jumper leads.  None is required since these are all nice strong "line level" signals - low impedance output and with a high signal level. 

I had a strip of double-sided foam-backed tape down the middle where I had stickers to label the connections.  This limits the number of holes which can be used, so I allowed only one hole on the left, since this was the input.  This left four holes on the right for each output.

Audio patch bay made with solderless breadboard

Audio patch bay made with solderless breadboard

This system worked like a charm.  I never had a problem with crosstalk or a bad connection.

 I used it for many years, and if I was building another studio I would probably do it the same way - except for these pesky cable nylon labels, which kept tangling other cables.