I love experimenting with the interconnections of my synthesizers, Eurorack modules, effects pedals, guitars, and controllers. Each experiment almost always adds exciting new sounds and techniques to my sonic arsenal. There is, however, an issue that has to be resolved pretty much every time this eclectic collection of gear is connected together: How do I connect gear that has different plug and jack types?
At this point, it would be helpful to present a quick recap of the standard audio and control plug/jack types.
1/4-inch (TS or TRS)
This is the plug/jack type typically found on guitars, guitar effects pedals, and the left and right output jacks found on regular-size keyboards and synthesizers. These gear types typically call for unbalanced (2-conductor) Tip/Sleeve (TS) connections as there are only two wires involved. (To be exact, it’s really two conductors — a single wire surrounded by a sheath or shield of braided wires.) Quarter-inch cables can also come in a Tip/Ring/Sleeve (TRS) configuration. The two main uses for this cable are either for connecting two balanced pieces of gear or for connecting a single stereo output jack (or headphone jack) to gear that has a stereo Audio In jack.
1/8-inch (TS or TRS)
This is the plug/jack type typically found on devices that have a stereo output jack for portable headphones. It’s also often used to bring an external audio input source to synthesizers that offer that feature. Some synths’ audio input is monaural (TS), while other synths have a stereo (TRS) audio input jack. (Note that, although 1/8-inch is mostly compatible with 3.5mm Eurorack jacks, they are only slightly different in size.)
3.5mm (Typically TS)
This is the plug/jack type typically found on Eurorack synthesizer modules as well as on synths and keyboard controllers with control voltage (CV) in and out jacks. As mentioned above, although they look similar, 3.5mm plugs are slightly larger than 1/8-inch plugs. (And if you say “1/8-inch” in front of Eurorack enthusiasts, you will catch them, out of the corner of your eye, giving each other that look.)
Example 1
I often need to connect an Audio Out jack from a Eurorack module (which is 3.5mm) to the Audio In jack of an effects pedal (1/4-inch).
One solution would be to use a small adapter that has a female 1/4-inch jack on one side and a 3.5mm plug on the other end. You could then put this adapter on the end of a regular guitar cable (1/4-inch to 1/4-inch). This will work, but . . . with my five decades of experience, I’d warn you that this is the most problematic adapter type I’ve ever used. The signal (either audio or control voltage) always seems to cut out every time the cable is bumped. The reason is the weight of the cable resting on that 3.5mm connector.
A better solution for connecting 1/4-inch gear to 3.5mm gear is to get an adapter that’s 1/8-inch female on one end and 1/4-inch male on the other end. You would then connect that adapter to one end of a 3.5mm Eurorack cable. This adapter has caused far fewer instances of signal interruption than the previous adapter I mentioned.
But, in my opinion, it’s almost always worth the effort to obtain a cable that already has the correct (but different) end types. It’s so much more reliable and convenient than having bulky adapters hanging from one end of a cable. And don’t forget to make sure that the cable is long enough for your typical uses.
Example 2
I really like using self-powered Bluetooth speakers when I’m tinkering with my interconnection experiments as they’re easy to move around, don’t require external power (usually, they are battery powered), and sound pretty darn good at low to medium volume levels. These speakers almost always have a single 1/8-inch stereo TRS input jack. Since I always seem to have stereo 1/8-inch TRS cables lying around, it’s good to have several female 1/8-inch TRS to male 1/4-inch TRS adapters that will allow direct connection between keyboards and portable speakers. But, again, if you know you’re always going to need this, then you’re better off with a cable that has each of the correct ends. You can even get ridiculously long 1/8-inch TRS extension cables to connect your keyboard to a speaker much farther away.
Example 3
I often connect the stereo (TRS) headphone out of a device to something that has separate left/right input jacks (either a mixer or a stereo effects pedal). One convenient thing about doing this is that you can use a single cable between those two stereo devices. If one end is 1/4-inch TRS and the other device has a pair of 1/4-inch TS inputs, then you can use an easy-to-find “insert cable” (looks like a standard Y-cable, but the Tip and Sleeve are wired to one 1/4-inch plug, and the Ring and Sleeve are wired to a different 1/4-inch plug). If your stereo headphone jack is 1/8-inch TRS but your pair of input jacks are 1/4-inch TS, then I would strongly recommend buying a cable that’s already configured that way as opposed to using an adapter.
Example 4
Sometimes, during my audio experiments, the very last thing in the audio chain is a stereo guitar effects pedal. If I want to use headphones directly out of the pedal, then I use an adapter that has a pair of male 1/4-inch TS plugs (one is usually red and the other is black) on one end and either a female 1/8-inch TRS or 1/4-inch TRS jack on the other end (depending on the size of the headphone plug).
I would be remiss if I didn’t point out that, aside from the physical connector differences, there are also signal-level and impedance differences. In the world of professional audio recording, these differences are addressed with direct boxes (DIs), level shifters, and impedance matchers. But, when you’re just having fun, the rule is to lower the output volume of keyboards and synth modules until they no longer distort your guitar-pedal effects. I know, it’s not “professional”; but I’ve done that during many of my hundreds of video demonstrations with only the occasional moment of clipping.
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