From Struthi to balanced inputs on an audio interface?

I’m seriously contemplating purchase of an audio interface and a DAW to use with a planned collection of Mutable Instruments devices, initially a pair of Struthis (kits about to be ordered, now that I have just sold my Roland MC-202 on eBay for a surprisingly handsome sum), but maybe an Ambika and/or some MI Eurorack later. Oh, and also input to the audio interface from my beloved Digisound-80 modular. The DAW will be Logic Pro X (I only use Macs, and given the capabilities of Logic X, the value seems unbeatable), and the audio interface will be a Behringer FCA1616 (adequate quality for my purposes, has an ADAT interface for potential future use with an Expert Sleepers ES-3 with MI and other Eurorack in mind, has 8 line inputs, and is also great value): product blurb

The Behringer blurb for the FCA1616 says:

“[Rear] inputs are balanced 1/4” jacks that accept a wide range of line-level devices. Outputs accept both balanced and unbalanced 1/4" connections."

The four front inputs appear to be balanced combination XLR/6.35mm TRS jack sockets for either mic or line inputs.

OK, here are my naive questions: what do I need to connect the output from Struthis (and later an Ambika), which appear to use 6.35mm unbalanced line-level sockets, to the audio interface? Will I need a balun or DI device to convert the unbalanced line-level signals into balanced line-level input for the audio interface? If so, what type (and recommendations?)?

I have posted a version of this question on Muffwigglers as well, with more emphasis on the Digisound modular, as befits the predilections of that site.

“He who can do more can do less”. Plugging a simple unbalanced 1/4" jack into a balanced input just works.

Qui peut le plus, peut le moins! So I don’t have to solder any custom cables…

Why it works:

Balanced inputs consist in sending +signal on the tip and -signal on the ring. The receiving device (mixer, audio interface) then uses the difference between tip and ring, which is twice the signal. The point is that any additional noise/interference that found its way on the cable gets eliminated or highly attenuated by the subtraction since it will have equally affected the +signal and -signal paths.

By using a mono cable, the tip will have +signal and the ring 0V, so you’ll only suffer form a 6dB loss which can be easily compensated on the receiving device.

Hi BennelongBicyclist!

Pichenettes has already provided the perfect answer re plugging unbalanced outputs into balanced inputs, but I added more detail about synth output levels yesterday to this other thread that you may find useful:

Synths output level

Hope it helps!


Just remember to keep the cable run under 75ft if you can. :wink:

@herrprof: As the Shruthi has a very hot/loud output - 75ft may be acceptable. I always try to keep my connections below 25ft if possible. In my experiences, 20ft of cable is enough to sap some of the higher frequencies out of your signal.

Many thanks everyone! I now have a much clearer understanding of balanced connections, and that one only needs to worry about them if one is using electromechanical devices like guitars and microphones, or if your mixing desk is at the back of the concert hall. None of those apply in my case. No need for microphones when you’ve got Vocaloid, right?

…and if you ever run into ground loop problems, balanced connections can be life-savers.


Ah… just remove the GND/Shield - and pray :wink:

Somewhat related, I just bought a bunch of stereo cable but the shop was out of trs ends. So I’m making a bunch of mono cables anyways.