Line level input vs. DI
- Thread starter JTC111
- Start date
A DI generally takes an instrument level in, and bumps it up to a line level output.
Instrument pickups are generally passive devices that only generate a very small voltage from magnetic differences created by vibrations in the conductor or the field surrounding it... These need to be amplified to a useable level...
The same holds true for a dynamic microphone, and to a similar degree to a condensor mic (which is not passive in design, but still need additional amplification)
andydeedpoll
i do love smilies...
My understanding was that a DI turn a signal from an unbalanced signal to a balanced signal. So a bass guitar going straight to the PA would have an unbalanced signal coming out of the bass, but if you put the bass into a DI box first, then you get a balanced signal, and all the positives associated with that? But I might be wrong.
Andrew.
Farview
Well-known member
You are confusing a DI box with the DI input of a preamp. Two slightly different things.
JTC111
Active member
So a DI is for an instrument like a bass or an acoustic guitar with a pickup. What would someone use a Line Level input for?
This would take the output of a preamp... and you won't find one on a stand alone preamp...
Some channel strips will include a line level input to access the compressor and/or eq as an external insert (typically bypassing the preamp).
JTC111
Active member
Actually, all the OSA 500 series pres have line level inputs.
http://www.atlasproaudio.com/osa2.html
But they give the option of upgrading the line level input to a DI input. So I'm trying to figure out if I'd ever have any use for the line level input. I have no idea what it's used for.
NL5
Unpossible!
I would get a basic engineering book and do some reading.
JTC111
Active member
Maybe I do get it but I just don't know it. Would/Could a line level input on a preamp be used this way? Suppose you created a midi track, converted it to audio, and wanted to 'color' it. Would you send that audio track from the mixer through the line level input? Is that it's purpose?
NL5
Unpossible!
The line level input will, in most cases, bypass the preamp circuit all together.
TexRoadkill
Audio Bum
DI's convert from unbalanced instrument or line level to balanced mic level (not line level). You still need a mic preamp after the DI.
The purpose of a DI is to convert the signal to balanced mic level so that firstly, you can use a mic preamp to up the level and secondly, so you can run the balanced signal over a longer cable run (like through a snake on the stage or tracking room and into the mic preamp) and not worry about losing signal strength and/or picking up RF interference from a long unbalanced cable run.
You can input either instrument or line level (the latter is usually from a keyboard or FX box). You don't have to use a DI if the preamp has 1/4" inputs and your cable run is only a few feet (around 6 ft or less is a good rule).
If your original output is line level (keyboard or FX) and you don't have a long cable run to the recorder inputs then you don't really need a preamp at all unless you just want to use it for the sound or the output level on the keyboard/FX is extremely low.
It sounds like there is some confusion going on between instrument level versus line level .... and balanced versus unbalanced.
To use an example ... a bass guitar signal is going to be coming in on an unbalanced cable at instrument level (in most cases, assuming it has passive pickups, etc.).
In order to get a good recording of it, you need to boost the signal up to line-level. This requires a preamp of some sorts -- to "amp" it, bassically. Up to line level.
Now whether or not this will require a DI ... depends entirely on what kind of input this "preamp" has. If the preamp has an unbalanced quarter-inch input, then you're set, and you don't need anything else. Unless of course you're doing a long cable run -- in which case, you'll want to run it in to a DI to balance the signal.
On the other hand, if all you have are balanced inputs (microphone / xlr), then you'll need to use a DI to balance the signal regardless. ... THEN you amplify the signal to line-level with the preamp.
Make sense?
To use an example ... a bass guitar signal is going to be coming in on an unbalanced cable at instrument level (in most cases, assuming it has passive pickups, etc.).
In order to get a good recording of it, you need to boost the signal up to line-level. This requires a preamp of some sorts -- to "amp" it, bassically. Up to line level.
Now whether or not this will require a DI ... depends entirely on what kind of input this "preamp" has. If the preamp has an unbalanced quarter-inch input, then you're set, and you don't need anything else. Unless of course you're doing a long cable run -- in which case, you'll want to run it in to a DI to balance the signal.
On the other hand, if all you have are balanced inputs (microphone / xlr), then you'll need to use a DI to balance the signal regardless. ... THEN you amplify the signal to line-level with the preamp.
Make sense?
The OP was specifically questioning levels, I was commented on the DI (instrument) input level of a preamp... which I believe was answering the question. I should have been more specific.
And yes the pricipal role of a stand alone passive DI box is to balance an unbalanced line.
JTC111
Active member
Kinda sorta.
Maybe I should start over with a different question.
Let's forget about DI for a minute. The OSA 500 pres give the buyer the option of a 1/4 inch DI input or a 1/4 inch line level input. So here's the real question: what would I use the line level inputs for?
I think I'll understand this better if I'm given a specific practical example of an application rather than an overview of how it works.
Much thanks and lowly bows to whoever can do that for me.
NL5
Unpossible!
Where is the "color" coming from?
JTC111
Active member
I think I made the original question too convoluted (I have a gift for that). I think I fixed that in the response to Daisy.
NL5
Unpossible!
I think you wouldn't need to ask the question if you had a simple grasp on audio basics. I don't mean that to be condescending, just as a fact. A "line level input" is for inputting a line level signal. It's that simple. A DI is to connect an instrument directly to the preamp. It will be looking for a lot lower level signal, and will show the proper impedence to the pickup.