I have a Scarlett 4i4 Audio interface and I would like to plug my Acoustic guitar in one of the two back side lines (and keep free the two in front for two mics), I have understood that I need first to plug my guitar to a Direct Box to lower the impedance, and then connect the Direct Box to the back side lines.

So now I should choose a Direct Box, and I would like to know what kind of box I should actually choose. As I see the two back side lines (lines 3-4) of the Scarlett 4i4 has an input impedance of 44Ω, and the most of the boxes has an output impedance of ca. 600Ω. Will it work? Or what should I choose for fix the problem?

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    Oh dear, it looks like you misunderstood what was established at music.stackexchange.com/questions/118016/…. Direct box helps you plug an instrument into a mic input, an XLR. The line-level inputs are for things like synths, external sound systems, maybe a CD player... I'll let someone more knowledgeable than me say whether there's a way to salvage the situation, but the only thing that springs to my mind is getting a small mixing board involved (not a bad idea), or maybe an amp that has a line-level output. Oct 22, 2021 at 12:12
  • One other bit of advice: I'm not a "sound guy," and there's a lot I don't know about inputs, outputs, cables, etc. Before I buy gear, I'd want to get the guidance of a professional who's actually paid to help me make these decisions. If you're lucky enough to have a robust, reliable local music store that hasn't been driven out of business by Guitar Center, by all means give them your patronage. There are also a number of mail-order places like Sweetwater that will take the time to hand-hold you through the process. Oct 22, 2021 at 12:19

1 Answer 1


Andy is right, you don’t want a direct box for this.

If your acoustic has an active pickup (with a battery that goes into your guitar), then you can plug straight into the line in on the back of the Scarlett.

If your acoustic has a passive pickup (no battery), then you’ll have to get an external preamp to go between your acoustic and the line inputs on the back of the Scarlett. Note that some preamps are also direct boxes, but most direct boxes are not preamps. So search for “acoustic guitar preamp” or something similar.

  • 1
    I have an active pickup on my Taylor GS Mini, a Taylor ES-B to be precise, with two CR2032 of 3V each for a total of 6V, do you think the impedance will be low enough to be plugged directly in the lines on the back of the Scarlett? Or should I go for a preamp?
    – Tiberius
    Oct 22, 2021 at 21:12
  • @Tiberius Since you already own the stuff without the preamp, try it and see if it works. You can’t break anything by plugging it in. Oct 23, 2021 at 19:20

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