Line/Instrument Inputs - what are they for?

My audio interface has line/instrument inputs. What is the line input used for? And the instrument input, can I plug in a midi keyboard or is that just for guitar? And if I pick up a synthesizer, what is the preferred input to plug it into?

Line/instrument input are basically the same - for keyboard/synthesizer with 1/4 inch jack output, either stereo (using 2 inputs pan left/right) or mono. You can also plug in the CD player output, via RCA plugs (red/white) to 1/4 inch cable/converter to line input.

Some line/instrument input also has a button to engage the 'hi-z' - this is for guitar/bass to plug in directly.

Without the 'hi-z' button, you probably need to plug the guitar to a direct-box, and the direct-box output to line/instrument input.

At times, without a direct-box, I do plug in my guitar to my mixer's line/mic input (accepts both XLR and 1/4 inch plug) and use the mic gain to boost the signal.. but I'm probably doing it the wrong way.

Line inputs expect to see a certain signal which is different than mics or guitars.  When people talk about "preamps" they usually mean a piece of hardware that amplifies a small signal - like that from a mic or guitar, into a line level signal.  It preamplifies the signal so your amp can play it - if you plug a mic or a guitar directly into your stereo monitor you are not likely to get much of a signal out from the speakers because the signal it is receiving is too weak.

Most synths have line level outputs that can be plugged into a mixer w/o any preamplification like they have built in for mics or guitars.  Same for your audio interface.

tomixornot


Line/instrument input are basically the same - for keyboard/synthesizer with 1/4 inch jack output, either stereo (using 2 inputs pan left/right) or mono. You can also plug in the CD player output, via RCA plugs (red/white) to 1/4 inch cable/converter to line input.

Some line/instrument input also has a button to engage the 'hi-z' - this is for guitar/bass to plug in directly.

Without the 'hi-z' button, you probably need to plug the guitar to a direct-box, and the direct-box output to line/instrument input.

At times, without a direct-box, I do plug in my guitar to my mixer's line/mic input (accepts both XLR and 1/4 inch plug) and use the mic gain to boost the signal.. but I'm probably doing it the wrong way.

Sorry, this is mostly wrong.  There is a big difference between instrument and line inputs.
 
A line input is designed to accept a "hi power" signal from a piece of powered equipment, CD player, synth, etc.  Anything that has it's own power source and provides an "amplified" signal (at line level) as compaired to a microphone output.
 
An instrument input is high impedence (Hi Z) and is designed for passive guitar pickups and other similar transducers that produce voltage levels of the same order as line level, but at very low power.  The low impedence (Low Z) of a line input would drag down the voltage produced by a guitar pickup, making the signal quiet and also affecting the "tone" by interacting with the tone capacitors in the guitar.
 
A passive DI box is basicaly an audio grade transformer that provides a Hi Z input for your guitar and a MIC level output.  An active DI box contains an amplifier and can provide a true line level output.
 
 
The inputs on some audio interfaces are often marked as Line/Instr.  In this case there should be a button to switch between the two, often marked Hi Z.  If you plug your guitar directly into the interface you need to select the Instr/Hi Z option.
If you use a seperate DI box you  use the mic or line input, not the instr input.

tomixornot

At times, without a direct-box, I do plug in my guitar to my mixer's line/mic input (accepts both XLR and 1/4 inch plug) and use the mic gain to boost the signal.. but I'm probably doing it the wrong way.

The XLR is your mic input and goes first through a pre-amp to raise the signal to Line level, then to the gain control and main pre-amp.

the 1/4" is the Line input and connects straight to the gain control section, bypassing the Mic pre-amp.

Karyn

tomixornot

At times, without a direct-box, I do plug in my guitar to my mixer's line/mic input (accepts both XLR and 1/4 inch plug) and use the mic gain to boost the signal.. but I'm probably doing it the wrong way.

The XLR is your mic input and goes first through a pre-amp to raise the signal to Line level, then to the gain control and main pre-amp.

the 1/4" is the Line input and connects straight to the gain control section, bypassing the Mic pre-amp.

Karyn,


Thanks! I can see my description is full of flaw.. :(


With my older Alesis Multimix interface, part of the mic inputs shares with line inputs, which is exactly what you described. 

With my new Roland Quad capture, one of the input can handle mic, line and also have a hi-z switch.. that makes me conclude there are the same (which is wrong as you pointed out).. depends what you plug in and switch to :)

Thanks again, with apology to the OP.

Until you understand the concepts, it is easy to get confused since some companies seem to label line/instruments as the same thing.  But as Karyn points out, the first difference is if the connector is powered from the source.  If not, it needs some kind of preamplification.

@

I go with the " if it fit's the hole, It must be right" thinking ( just kidding).........

You'll find some pretty amazing hook up's when you go and trouble shoot places like community halls or small churches. If they can find an adapter or gender bender and some kind of sound comes out the other end, they figure they got it right. 

Here's my seat of the pant's user guide to all things audio----
If I have to turn it up to 10 or down to 1 then I  will look for a button or knob or another orfice. 
 I truely feel gain knobs need to be either side of noon and no red lights before all is good.
I might be guilty of always ignoring the printing on front panels. I always thought they put "instrument" on there just to remind you that your a musician and to keep all others away.

What if I'm using my RP1000 into a Saffire 6 USB, should I use Instr., or will the RP, give it the power needed? The reason I dont just use the RP1000 USB, is because I already have MIDI controller, and JBLs hooked up to the Saffire.
 RP has no midi, I figure guitar into input on RP, then Left Line Out( Mono) to !/4" on my Saffire, there is an amp/mixer switch next to line out on RP, I assume amp would be choice. Sorry for jumping in, just don't want to fry brand new toy, Thanks!

gray36


What if I'm using my RP1000 into a Saffire 6 USB, should I use Instr., or will the RP, give it the power needed? The reason I dont just use the RP1000 USB, is because I already have MIDI controller, and JBLs hooked up to the Saffire.
RP has no midi, I figure guitar into input on RP, then Left Line Out( Mono) to !/4" on my Saffire, there is an amp/mixer switch next to line out on RP, I assume amp would be choice. Sorry for jumping in, just don't want to fry brand new toy, Thanks!

The outputs from the RP1000 are going to be LINE level using MIXER output.  you would plug the outputs into the inputs of the saffire, but NOT use the INST buttons. 
 
AMP level is going to be lower signal, so you could hook it up that way using INST, but I'd just use the LINE output (MIXER) of the RP1000 into the saffire with the INST button OFF.

Last question, promise, either method will still give me the Amp/Modeling, and effects,etc., that make the RP what is... a Multi-effects pedal? Like I've mentioned before, I have plenty of good software amp sims, but want it on the floor, because of back problems. Thanks again!

I would assume so, but I don't know that, I don't own an RP1000.  check the manual to be sure.

but also be aware that a lot of the modelling and effects are stereo output, so only using the left/mono will not be the full FX.

Please forgive my ignorance, I never thought of that! What the hell, I give up, manual just shows using built-in interface. What if I ran 2 lines, 1 out l/o, 1 out r/o, and into the 2 inputs on Saffire? Not much, being mono signal from guitar? I'll take another look, surely to God, they would have thought of that...but we know what assuming means! Thanks again!

yes, running both outputs of the RP into both intputs of the Saffire will work and would give you the stereo effects whenever the RP is using stereo FX.  then just set up the audio track in sonar to record the STEREO input 1/2 instead of LEFT.

That's the answer I was hoping for, thanks Beagle!!!