What's a Studio Guitar Interface? Well, the SGI allows us to take an electric guitar, or any high-impedance, unbalanced instrument signal, and send it down a balanced signal path (think mic cables, snakes, or studio tie-lines) to an amp or processor. It does so with two small, stompbox-sized units - one at each end. The SGI-TX is the transmitter end, powered by a wall wart. The instrument plugs into a 1/4'' jack, the output is via male XLR. At the other end of the balanced line is the SGI-RX receiver, which has a female XLR input, 1/4'' output, and does not require power.
The concept is simple: Think of this as running a guitar into an active DI box, sending a line-level signal down a mic cable, and then putting a re-amp box at the end to bring the level down and the impedance up to mimic the natural output of the guitar. If you have spare DI and re-amp boxes, you could set this up, sure, but let me digress: For me, work in the studio has to happen fast. Setting up your own studio-quality DI to re-amp configuration, and gain-staging them properly takes time. On the other hand, the SGI has no level or attenuation controls. My experience using the SGI on hectic sessions has been "plug it in and go," with no worries or problems. The only options are minimal and handy. A "drag" potentiometer on the SGI-TX allows you to adjust the impedance load that the guitar sees, allowing you to immediately tailor the sound of the guitar. In practice, I almost always found myself leaving this set full clockwise, and not using it, and getting pretty much the same sound to my amps as if I was plugged directly in. The other control available is a simple ground-lift switch on the SGI-RX, which allows you to avoid ground loops. I found myself lifting the ground more often than not, so I'm glad Radial included this.
The SGI is built tough, like all Radial products, and internally uses quality transformers for isolation and Class A circuits for buffering. In use and in tests, I could not differentiate between guitar tones that were run through the SGI or not, even when routing multiple 100 ft patches all over my studio (300 ft is the claimed length limit). I imagine some guitar tone purists might be able to discern some change in the tone, but I can't, and I listen to the sound of recorded guitar amps day in and day out. The real benefit in the studio is the flexibility. I can put a singing electric guitarist in an iso room and put his or her guitar in a room across the studio, plug the SGI units in via two XLR tie-lines, jumper a TT patch in the control room, and their guitar signal shows up perfectly in the other room. (Make sure to buy some XLR male "same sex" adapters, or make a dual-male cable for the receiving end.) No more compromised runs of long high- impedance guitar cables under the doors and across the room. The other main use I get out of the SGI is to have a musician come into the control room, and use the unit to send signal to their amp in the live or iso rooms. The great thing is that the SGI-TX is the only unit that requires power, so it can sit with you in the control room, as you drag the SGI-RX from amp to amp, out on the floor. Now that is working quickly and efficiently, especially when doing quick punch-ins after a live take (another situation where I did not hear a tone or level difference between direct amp and SGI connections). Of course the SGI can also be used by our live-sound brethren to run long instrument leads in live settings, and to run a direct instrument signal to front of house for processing if needed. Handy.
This is just another in a long line of Radial products that efficiently and elegantly make work in the studio a little easier and quicker. Real problem solving.