Sunday, October 1, 2017


by Mark King for


I have a lot of wiring in my studio that uses Tip-Ring-Sleeve TRS connectors. I also have a lot of unbalanced phone plugs on guitar cords. I came up with this handy little problem solver a few months back and just built three more.

It's two TRS jacks in a die cast aluminum enclosure. I use 16 gauge wire for the connections so they can handle anything from guitar to line-level to speaker signal-levels. I use isolated 1/4" jacks for this project because I don't want the exterior of the TRS-Thru enclosure to be at ground just in case it might bump into something else that is grounded (which would cause hum, noise or some other annoying problem).

Technically the connection is not shielded through the handy-box if there is no ground connection to the enclosure. In months of actual use with several of these TRS-Thru boxes I've never had a problem with the box not being part of the electrical shield.

The uses for these boxes are seemingly endless, they work with TRS type plugs and TS type plugs found on guitars and stomp boxes.

Here are a few of my favorite uses but I'm sure you'll find more.

I've never found reliable headphone extension cords, the female jack end always fails. I have standard TRS to TRS cables in multiple lengths for use with the patchbay.
Handy-box Solution: Connect a 20-foot TRS-to-TRS male cable with a TRS-Thru handy-box on the end and you've got a killer reliable headphone extension cable.

My Leslie has a 15-foot cable on the foot-switch that changes speed from high to low, it's just a bit too short.
Handy-box Solution: Use a 10-foot guitar cord and TRS-Thru handy-box to lengthen the footswitch cord.

I like to use short guitar cords in the studio but sometimes I'm just a few feet too short.
Handy-box Solution: Use a TRS-Thru handy-box to splice two guitar cords together.

When I end up with two TRS cables that need to be connected together I grab a TRS-Thru handy-box. This happens a lot because I use XLR to TRS converter cables quite often and I end up with two TRS male cable ends that need to be joined, TRS-Thru handy-box to the rescue, it is made to join TRS plug to TRS plug.

I don't generally like 1/4" phone connectors for speaker cables but they are what most tube guitar amps have on the back and unfortunately I sometimes need to lengthen the speaker cable a few feet.
Handy-box Solution: Use a TRS-Thru handy-box to connect 1/4" speaker cables together to extend the cable run.

Sometimes I want to connect the unbalanced output from a stomp box into a balanced input.
Handy-box Solution: run a guitar cord from the output of the stomp box into the TRS-Thru handy-box, run a TRS cable from the other side of the handy-box to the balanced input.

Mammoth Electronics is where I buy these enclosures, they have good inventory and prices. They also have a lot of other parts for builders.

I order these isolated Switchcraft TRS jacks from Redco.

The wire is from years of collecting and carrying it around. If I needed more I'd buy Teflon coated Mil Spec wire from the guy on eBay. His prices are 1/3 the wholesale price, he delivers fast and the product is great. Otherwise you can buy wire at Home Depot and use that.

Just be sure to connect the Tip to the Tip, the Ring to the Ring and the Sleeve to the Sleeve.

Keep your connecting wires short or else it's hard to get thick wire to bend in to the small space of these compact die cast aluminum enclosures.

My friend and fellow installer Paul Graves, has reminded me that as-wired above, if you use these to join unbalanced instrument level cables (like guitar cords) these could be susceptible to electrical interference in harsh environments. We're not having any problems with them in the Proworkshop recording studio but that does not mean it could not happen.

If you want the best performance against RF in one of these little boxes then use Gotham double shielded cable to join the two TRS jacks, you can order it from Redco (warning that double shield is a real bear to work with but it is stone quiet RF wise).

If you use shielded cable for the interconnections between the TRS jacks I still recommend not connecting the enclosure to the ground of the jacks for two reasons: One: the enclosure is aluminum which provides only minimal shielding anyway. Two: not connecting the audio ground to the enclosure isolates the shield and electrical circuit ground instead of exposing it to any possible random contact with other grounded objects which could possibly cause ground loop hum and buzz.

TRS-THRU BOXES that are wired with shielded cable are not suitable for speaker cable to speaker cable connections. Some amplifiers don't like shielded wire to be used for outputs and the conductors are too small for todays lightweight high-power class D outputs. But if you need to join guitar cables regularly then using premium shielded cable inside is recommended.

Build yourself a few of these TRS-Thru boxes and you'll find lots of uses. They are rugged as can be and last forever. Enjoy!

Good music to you.