Line inputs and outputs

[danjags]

Hi, i have a scarlett 6i6 interface and am trying to figure out the best way to use it with logic and the devices i have in my studio. A bit confused about how line inputs and outputs work, so two questions:

1. should i be able to plug a electric guitar into the line input (with a standard guitar cord) and hear the same sound as i would if plugging it into one of the front inputs (that have the knobs to adjust volume next to them and also have the xlr ports?). When i plug the guitar into the line inputs, i am hearing much lower volume and there is no waveform in logic as i'm recording (whereas there is when i plug it into the front xlr ports). Is this supposed to be happening? Is the electric guitar good to use in the line input ports or are these for something else? Do i need to change some sort of setting within logic to make it work right?

2. if i plug my headphones one of the line output ports on the back, is that the same as plugging the headphones into the headphone ports in the front? do line output ports output to stereo or mono if you have headphones plugged into one of the ports?

 

[danjags]

also, the line outputs on my interface don't have volume knobs like the headphone ports on the front of my interface. is there any way within logic to adjust the volume of a specific line output? can this be done in the mixer?

thanks,
Dan

 

[Pete Thomas]

Hi, i have a scarlett 6i6 interface and am trying to figure out the best way to use it with logic and the devices i have in my studio. A bit confused about how line inputs and outputs work, so two questions:

1. should i be able to plug a electric guitar into the line input (with a standard guitar cord) and hear the same sound as i would if plugging it into one of the front inputs (that have the knobs to adjust volume next to them and also have the xlr ports?). When i plug the guitar into the line inputs, i am hearing much lower volume and there is no waveform in logic as i'm recording (whereas there is when i plug it into the front xlr ports). Is this supposed to be happening? Is the electric guitar good to use in the line input ports or are these for something else? Do i need to change some sort of setting within logic to make it work right?

No, I believe the instrument inputs are what you need, not line inputs, a conventional guitar or bassdoesn't output at line level. (maybe active guitars do ??? )

2. if i plug my headphones one of the line output ports on the back, is that the same as plugging the headphones into the headphone ports in the front? do line output ports output to stereo or mono if you have headphones plugged into one of the ports?

I don't know that exact interface, but I think that normally the front and back would be the same.

also, the line outputs on my interface don't have volume knobs like the headphone ports on the front of my interface. is there any way within logic to adjust the volume of a specific line output? can this be done in the mixer?

Yes, you can do that in the mixer. (obviously not the line level signal after D/A conversion, you can adjust the output level in Logic (or any DAW) before conversion to analogue.

 

[Peter Ostry]

I don't know the Scarlett interfaces but can answer some questions according to the tech specs published by Focusrite.

1. should i be able to plug a electric guitar into the line input (with a standard guitar cord) and hear the same sound as i would if plugging it into one of the front inputs (that have the knobs to adjust volume next to them and also have the xlr ports?)

Plug a standard guitar cable into one of the combo jacks at the front of the interface. Then configure this input via the control software as INST. See the manual, page 9. This configuration gives you max. 50 dB gain and an input impedance of 1 MΩ.

Guitars do seldom send signals on line level and the impedance of a line input is too low for a guitar pickup, even for active guitar electronics.

First, you need some gain and this is provided by the potentiometers at the front inputs. Second, you want a high impedance to preserve your guitar tone. Passive pickups expect at least 1 MΩ, active pickups are usually happy around 500 kΩ. Rule of thumb: the more, the better. The Scarlett's line inputs have only 52 kΩ which is perfect for line connections but not for guitars.

Btw, instrument inputs of interfaces are just one method to connect guitars and other instruments. Other ways are DI-Boxes, external preamps and special outputs of guitar amps.

2. if i plug my headphones one of the line output ports on the back, is that the same as plugging the headphones into the headphone ports in the front?

A standard configuration for interfaces is a headphone output with a built-in headphone amplifier and adjustable gain. This is what your Scarlett has and you should use it. The Scarlett's phone output fits to all headphones suitable for studio work.

Technically it depends on your headphones. Again the impedance thing: A Scarlett line output (the sending device) has 94 Ω impedance. The receiving device (your headphones) should have at least 2x this impedance, means about 200 Ω. How much do your phones have? 50 Ω, a standard value, are too low. 250 Ω headphones would work. Although I am not sure if you would get them loud enough. Such headphones are made for strong headphone amplifiers.

Line signals are not intended to drive speakers, and phones are speakers, basically. To hear a line output you go to an amplifier, be it an active loudspeaker with it's built-in amplifier or a headphone amplifier.

do line output ports output to stereo or mono if you have headphones plugged into one of the ports?

The line outputs are mono.

If you want to feed your phones by line outputs, for example to connect more headphones or for better quality, look for an external headphone amp. They are available from 1-8 channels in different configurations, sound quality and price classes.

also, the line outputs on my interface don't have volume knobs like the headphone ports on the front of my interface. is there any way within logic to adjust the volume of a specific line output? can this be done in the mixer?

As Pete said, the output level is controlled by the DAW. In Logic you can route any channelstrip to any available output channel.

Line outputs of interfaces don't have volume knobs because we expect them to deliver a certain level. You can always be sure that a line output delivers what you send to it.