Behringer GI-100 DI Box: The Measurement Results! 

Welcome!

Thanks!

Thanks! I agree, it works great for acoustic guitar.

This is an active di, so the designers could make the internal circuitry boost or cut the signal, and evidently they designed it so the same level signal comes out as went in. Well, real close, I measured a small 2 db boost as the signal passes thorough the DI. It doesn't change the sound, it's not a significant boost, just an observation as I was measuring. That minor behavior might also be specific to my individual unit. So, that minor signal boost is nothing to worry about.

I understand the concern, but no worries. The DI-100/GI-100 di box input impedance is very high, greater than 250K ohms. So it should not have any loading effect at all on the performance of the guitar, even with passive pickups.

Sure, you could plug guitar into the DI, and then have another cable from the DI to feed the amp. Of course by doing this you won't get any of the amplifier effects (distortion/tone) in the DI signal. I've often plugged the output of the guitar players pedal board into DI (then DI to amp) where the player isn't heavily relying on the amp provide effects & tone control. The advantage of this can sometimes be a cleaner signal, because some guitar amps speaker output may have a little bit of hum or noise on it.

I don't think I have a perfectly clear picture on exactly what you're trying to do. The DI box will provide isolation between pieces of equipment so that may be a benefit and may help prevent hum when connecting a computer to a guitar amplifier. Are you re-amping for a recording session? An active DI box is expecting a high impedance unbalanced input, and delivers a low impedance balanced output. A guitar combo amplifier is expecting a high impedance unbalanced source, so that's not ideal. In an active DI box, the signal only travels from input to the output. However, you could use a passive di box, which is really just a transformer, and run it backwards. Inserting the signal from your computer into the XLR connector on the di box (output) and using a guitar quarter to quarter cable from the input jacket of the DI box to the input connector of the guitar combo amplifier. This would probably require an adapter on the XLR side of the di box that would be a female to female or a funky cable with female connectors on both ends... This is assuming that your computer sound interface output is a balanced signal. If your computer sound interface has quarter inch balanced outputs, you could use 1/4 inch trs to xlr female, and that's a pretty standard cable. I'm making an assumption here and I may not understand your application exactly. If this doesn't address what you're looking for, let me know.