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I am a complete neophyte in recording, so I am very poor in theory. I am thinking of buying some hardware for some home recordings and I am faced with the first choice: the audio interface.

Since I will mostly record voice + acoustic guitar (so one mic and one inst) I see there are a lot of interfaces I can use since all of them support at least two inputs, but I will occasionally need to set one extra mic, so I was thinking to be focused on an interface which has more than just two inputs. I am for example evaluating the Focusrite Scarlett 4i4, and many others that have two line level inputs, so I am wondering if occasionally it will be fine to plug in the electrified acoustic guitar to those line level inputs (while connecting two mics to the frontal inputs).

I have a Taylor GS Mini-e with a ES-B pickup/preamp, I have not found information about its impedance. I even don't know what impedance is. I just know that it is something related with the output voltage (maybe??) and I know that the GS Mini ES-B has two CR2032 batteries of 3V, so a total of 6V output voltage.

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  • This might help for starters: service.shure.com/s/article/… Oct 20, 2021 at 13:35
  • In other words, most pickups (aside from a few that are actually mini-mics) should use the line-level input. Also, although we don't cover recommendations of specific gear here, I will say that I could imagine even a casual or solo user benefitting from four inputs vs two. Oct 20, 2021 at 13:37
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    Okay, and now I actually Googled the Focusrite Scarlet 4i4. I see the problem now; the two "high headroom instrument inputs" are in the middle of the XLR inputs, so that you can't use both simultaneously. Oct 20, 2021 at 14:40

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Not really. Both electric and electroacoustic guitars are usually high impedance instruments, and the instructions from Taylor website confirm that this one is too: "The ES-B is designed to be plugged in using a standard quarter-inch guitar cable, which will work with an acoustic guitar amplifier, a standard direct box, or any other guitar-ready application." Direct box is a device for transforming high impedance instrument signal to low impedance microphone level signal. The line level inputs at the back of Scarlett 4i4 are on the other hand low impedance.

Impedance is the ratio between voltage and current (if you don't know what they are, a daft car analogy would be that they're a bit like RPM and torque but different). The higher the impedance is, the less current there is for the same voltage. The guitar produces only roughly 1/100th of the current that comes from a normal line output, so it does not have enough power for a normal line input even if the voltage is the same.

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  • Wait, one of us is confused. The question was whether you can plug the guitar into the line-level "instrument" inputs. Oct 20, 2021 at 14:28
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    The difference between line and instrument inputs is impedance. Both have voltages somewhere near 1V, but line input impedance is typically in range of thousands of ohms and for instrument inputs it is hundreds of thousands. It is unlikely that a guitar can provide enough current to drive a standard impedance line input.
    – ojs
    Oct 20, 2021 at 14:34
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    And to clarify, the two line inputs at back of the 4i4 are standard line inputs. The ones on front have preamps for microphone or guitar.
    – ojs
    Oct 20, 2021 at 14:42
  • Thank you so much to both of you for infos. @ojs - so, would it be enough to connect my Guitar to the Direct box and then the Direct box to the Audio interface on the Line level input? If so, what are the main differences between an expensive Direct box and a cheap one?
    – Tiberius
    Oct 21, 2021 at 13:27
  • @Tiberius it's a separate question. Long threads are not appreciated on Stackoverflow.
    – ojs
    Oct 21, 2021 at 13:42

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