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Line or Mic input
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heilmann
Prenoob

Joined: 18/01/2011 03:51:36
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I have an early SL 16-4-2. I have a question in regard to the mic input vs. the line inputs on each channel. When I run a keyboard into a DI, I normally then send the XLR balanced signal thru the analog snake to the board. Sometimes it is line out, other times it is from the headphone jack. In both cases it goes to a DI. The output of the DI (XLR), and the snake, are setup to encourage me to connect it to the XLR input of the appropriate channel. Should an XLR to TRS adapter be used at the mixer to connect this signal to the line input rather than the mic input? I have the same question with the Bass input as well. I often come out of the bass amp line out that also is XLR and then travels to the mixer via an XLR connection.

Thank you in Advance,
Keith
sjc193
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Joined: 30/03/2012 20:51:58
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Location: Warren, PA
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I deem that a good question.

I'm thinking 6 in one, half a dozen in the other

I always use the XLR input in these cases and haven't had an issue, I just watch the meter and adjust the gain like any other channel.

Technically the difference is (and these numbers are made up, but in the ballpark maybe) when using the xlr in the gain goes from like 0 to +50db, when using the line in the gain knob goes from like -15 to + 15db, and I honestly think it might use the same xmax preamp to give you the + 15 if you need it, so it's not like it totally bypasses the preamp. So, that said, unless you need to go below 0 you shouldn't need the line in, and there are always -10 or -20 db pads on all these DI boxes anyways.

In a recording studio setting someone may get pretty anal about something like this, but my belief is that in a live setting it's standard to use the xlr in and if the signal is too hot, click a pad on the DI to get you a better level.

Please correct me if I'm giving out bad info here dudes, but I feel good about it.

Steve

This message was edited 1 time. Last update was at 08/04/2014 20:25:17

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b_dann_b
Presonic
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Joined: 09/03/2011 13:03:37
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Working this one out depends on what the DI is/what its doing. I'm going to use made up numbers here to provide you with some insight.

In general there are 3 common "levels" that you deal with (there are actually probably 4 but that's going to over complicate things).

They are Mic level, line level and speaker level. Each level uses a different voltage (using made up numbers):
mic level - 0.1V - 2v
line level - 4v
speaker level - 120v+

when you use the specific ports on a mixer they all aim to bring the signal you put in up to line level which is generally where the mixer works at within itself. When you plug a mic into a mic input on the mixer, because the mic only produces a small voltage a preamp attached to the other side of the socket on the mixer boosts the signal to line level. this boost is variable using the gain pot.

So in comes the DI. the DI does 2 things - converts the signal to a balanced signal (to reduce noise) and converts the voltage between the 3 types of levels depending on the DI in question (you do this using the pad buttons). So if you were to put a line level source into a DI and pad it once, it would bring it to mic level. If you put a speaker level and pad it twice, it would take it to mic level. If you put a mic into a DI and pad it, it would bring it below mic level (which is not something you would generally do).

(note that the above are random numbers just to explain the general workings).

So if you have line level coming out of your keyboard and you put it into a DI and pad it, it would be mic level and therefore best to plug it into Mic input. If you did not pad the signal it would be a line level voltage coming through the cable to the mixer. Whilst it may seem right to put it in the line socket on the mixer, it may not be the best way as your DI has balanced the signal and you are now plugging into an unbalanced socket.


Simple answer:
Pad you DI once. If your using headphone out, put the volume up to about 3/4 full and then plug into the mic/xlr socket and you'll be fine.

This message was edited 1 time. Last update was at 10/04/2014 01:56:12

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roblof
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Joined: 12/04/2011 21:33:08
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Some additions to the previous post.

Many pro instruments with line level has balanced outputs and the studiolive line inputs are balanced as well.

Since the line level is so much higher than the mic level noise interference is most of the time a non-issue. At least for normal cable runs...

A di can provide galvanic isolation between a mixer/recording interface and this can help with ground loop issues.

With this in mind I'd use the line inputs for home/studio use and di for live use.

Oh, and the xmax preamps are not in the signal chain when using the line inputs. The line inputs have a much simpler preamp design.
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heilmann
Prenoob

Joined: 18/01/2011 03:51:36
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Thank you everyone for your reply. A lot of good stuff to consider.

Keith
salvadoredelle
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Joined: 01/04/2011 17:49:43
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for the most part... and if you are using a quality active D/I box you should always use a MIC level input on you mixer for D/I boxes that have XLR +4 line level outputs ( that most likely will also need phantom power you only get via XLR mic input )... these are designed to use a mic input and you will get more headroom, better frequency response overall better performance and 48v phantom power. And not have to use an adapter to loose any of that!
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