Making a Passive Headphone (or source) Switcher
If you’re new to building DIY audio projects, this is probably one of the most simple and inexpensive projects you can build.
A good quality passive switcher similar to this one typically costs about $100, but you can build this for about $10 (plus the cost of a case which can be anywhere from $5 to $50 or more, depending on how much you want to spend on it). The necessary tools for this build are a Drill, 5/8″ & 1/8″ bits, a soldering iron & a screwdriver.
The purpose of a completely passive switcher is to route one source of signal to multiple outputs as cleanly as possible (without a power supply), using a good switch and the shortest possible paths to the outputs using good wire and soldered connections. The most important thing with any build project is first determining your needs and then finding the right components for it.
The Passive "Can" Switcher inputs
I built this one for three pairs of headphones I like to have available for mastering (each one gives me a range of accuracy to rely on) and while my Crane Song Avocet DAC/Monitor Controller has two outputs for the excellent headphone amp it has built in, I decided that it would save me time and also wear on the Avocet’s jacks if I had all my cans patched into a switcher and then just select the one I need any time.
The first thing I did was measure the holes needed for the jacks and switch & drilled them:
The hole in the back of the case is the input, and under the switch, a 1/8" hole is needed for a guide that's built into the switch.
Then, it was time to fit in the jacks and switch. I used a red “chicken head” knob I had around and fitted everything to make sure nothing was loose:
When researching the kind of wire used on the insides of high-end audio gear, I discovered that a lot of it is built using Teflon-coated, 18awg solid core silver plated copper wire. Sounds exotic and expensive, doesn’t it? Well, it’s hella cheap. I got some on eBay a while back (also a good place to search for a case) for a few cents per foot and used it for this build. Since the coating is clear, I used a few pieces of shrink tubing on all the ends to identify each wire:
A (Black) = Left, B (Red) = Right, C (Blue) = Shield
Now we move on to making the connections on the switch and jacks. Since I only needed three connections (left/right/shield) on the switch for the 1/4″ TRS connections on my headphones, a 3 pole switch was sufficient. I also wanted three outputs, so the switch I needed had to have at least 3 positions as well. While doing some research on the parts I needed for this build, someone put me on to the Lorlin brand of rotary switchers. Lorlin has either a 3 pole/4 position rotary switch that would have been perfect if I also wanted an “off” position, or a 4 pole/3 position switch.
I decided to get the switch with the least amount of positions (3) and kind of liked the idea of always having one of the cans switched on during situations where I would be using all three; the extra pole is simply not used.
The 1/4″ jacks I used were Neutrik jacks (I also used Neutrik 1/4″ connectors and the same SPC wire for the interconnect used for this switcher). This is how the jacks are soldered:
Black = Tip (Left), Red = Ring (Right), Blue = Sleeve (Shield)
I use Cardas Quad Eutectic solder for all my DIY Audio Projects, so provided that you make good soldered connections, you now have a completely passive switcher that will not degrade the quality of the audio you route through it. This is what the inside of the switcher looks like with all of the jacks soldered to the switch:
