How Should I Connect My Preamp to My Interface?

Joe Gilder | November 15, 2010

After posting the review of the Presonus Eureka, several of you asked me how to exactly connect an external preamp to an audio interface.

While this may seem simple enough, a lot of home studio owners are doing this wrong. It’s not the end of the world, don’t worry. However, you need to know the proper way to connect these things, since it might adversely affecting the quality of your recordings.

Mic Input vs. Line Input

What is the purpose of a preamp? Why does it exist? As I mentioned in Intro to Preamps, microphones produce a very low-level signal. Without a microphone preamp, the signal remains unusable.

A microphone preamp amplifies the signal from mic level to line level.

Most audio interfaces include anywhere from one to eight preamps. The inputs to these preamps are 3-pin XLR connections. You simply connect the microphone directly to the preamp via the mic input.

Most interfaces also include a number of line inputs. These accept line level signals.

Line level signals don’t need to be amplified by a preamp. They are already at the appropriate level.

Examples of devices that produce line level signals:

Microphone preamps (more on this below)
Compressors
EQs
Rackmount effects units (reverbs, delays)
Mixers
Keyboards
CD player/recorders

Connection Clarification

There are essentially 4 types of connections you’ll deal with in your studio: XLR, 1/4″ TRS, 1/4″ TS, and RCA. Any of these can be line inputs.

XLR and TRS are balanced connections. Most line inputs on audio interfaces are 1/4″ TRS connections.

TS and RCA are unbalanced connections. (More on this another day.)

Here’s the tricky thing. Mic inputs are also XLR connections. You can see how this could easily get confusing.

Hooking Things Up

Here’s a general rule of thumb: Connect microphones to microphone inputs, and connect line outputs to line inputs.

Let’s take the Presonus Eureka, for example. It has an XLR mic input, and that’s where I connect the microphone (obviously).

The Eureka also has both XLR and TRS line outputs (you can use either one). The back of my 003 has XLR mic inputs and TRS line inputs. Which should I use for the Eureka?

Answer: One of the TRS line inputs.

So, I use a standard 1/4″ TRS cable to connect the line output of the Eureka to one of the line inputs on the 003. If I wanted to, I could a cable that has an XLR female connector on one end (for the Eureka’s XLR output) and a TRS connector on the other (for the 003). Either one of these would work.

Line Output + Mic Input = Trouble

A lot of people run the line output of their microphone preamp into the mic input of their audio interface. This is unnecessary, because you’re essentially running the signal through two microphone preamps. This can result in distortion and a degradation of the sound.

I recently saw someone post on Twitter that they tried running their preamp to the line input instead of the mic input, and that it made an amazing difference.

It’s true, using the proper connections and gain-staging is very important when recording. Go check your rig and make sure you’re connecting everything properly.

Did this help? Got questions? Leave a comment.

[Photo by jennie-o]

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Darcy

How did I not know this? I have been connecting mics to preamps.. and then connecting the preamp to another mic input.
You have know idea how incredibly idiotic I feel.
Demetrius Ledbetter

how can o make my mic stereo going thru the eureka compressor

http://www.homestudiocorner.com Joe Gilder

You can’t make a mic stereo. A mic is mono…by definition.

eddie_higgins2009

So I have a xlr mic runnin to preamp then 1/4trs to eq then 1/4trs to compressor then 1/4trs to line input on maudio interface is this correct ? where do I put the eq/ compressor at? Is it in the correct set up

http://www.homestudiocorner.com Joe Gilder

That sounds right to me!

Joon

im using my line input on my interface from my pre, but the interfaces i have use combo inputs… xlr/line/instrument …theres a button that engages each function but i wanted to be sure that the rules you stated still aplly to interfaces like these

http://www.homestudiocorner.com Joe Gilder

You’ll have to read the manual to find out.

Garrett S

Thank you for the very clear explanation step by step. I running my microphone into the presonus studio channel and then trs out into the mic/line input on Komplete Audio 6 interface. I know understand that I need to press the button inward on the Komplete audio 6 mic input which changes the input to line level. That way I am only using the preamp of the studio channel and not the preamp on my Komplete Audio 6. I’ve been unknowingly using
2 preamps before. I haven’t noticed degradation in sound quality, but I am anxious to see what my sound will be now using only the preamp on the presonus studio channel. Thank you again.

http://www.homestudiocorner.com Joe Gilder

You’re very welcome. You might not notice an audible difference, but now you’re at least running everything “properly.”

Chris

Could you post a picture diagram for me of the correct hookups from an audio interface to a preamp? I’m still unsure of what I’m reading.

Thanks,

Chris

http://www.homestudiocorner.com Joe Gilder

Hey Chris. It might help to read the manual of your audio interface and preamp. They should both have in-depth diagrams for you.

Simon B

Hi there – great article and very helpful. But I still have a niggling question,as I’m a newbie setting up a studio, and don’t want to make an expensive mistake…
You suggest taking the line level out of a preamp and inserting into line input of an audio interface, as opposed to the mic input. I understand all of the rationale behind this. My confusion is that the line input on my audio interface (Creative X-Fi Elite Pro) DOUBLES UP as a mic input, or that’s how it’s labelled, at least. It’s not switchable, either physically or via the installed software.
Is there any kind of “conflict of interest” here? Or if I plug a line source from the preamp into it, will the unit automatically recognise that it’s a line signal (as opposed to a mic)?
Many thanks in advance.

http://www.homestudiocorner.com Joe Gilder

Not sure on this one. A lot of interfaces have a combo jack, so the 1/4″ internal section is the line input, and the XLR input is the mic input. Otherwise, I’d suggest reading the manual and seeing what the manufacturer says about it. Every manufacturer handles it differently.

Simon B

Many thanks for taking the trouble to reply, Joe. Much appreciated.

Sadly, the Creative interface came bundled with my pc – you guessed it….there’s no manual and I can’t find the answer by searching the internet for information specific to this interface.

(There’s no XLR input either)

Thanks again….

http://www.homestudiocorner.com Joe Gilder

If it came with your PC, then there’s a good chance it wasn’t really meant for recording. I’d get a good USB or firewire audio interface and go from there.

donald

hello quick question, im completely new to how any of this works and i just wanted to know something simple (yes im a amateur), i have a 48-phantom power that runs mxl v63 mic..do i need ANOTHER seperate 48-phantom power to run

ART Tube MP Studio Mic Preamp? or can i use one 48-phantom power to run both the mic, and the preamp?
Anita`

Hi, please can you help me. I recently bought the NAD 5120 turntable and after connecting it to my LG Mini Hi-fi found the sound quality very poor, was told to buy a pre-amp which i did, its a phono/mic pre-amp Please could you let me know how to connect that to the turntable and the mini hifi. I am clueless when it comes to these things.
Thanks alot!

http://www.homestudiocorner.com Joe Gilder

Hi Anita,

I don’t know anything about Hi-Fi. I’d contact someone who does. This site is all about recording music in a home studio. Good luck!
Joe

miah419

Ok so i bought this Blue baby bottle mic for studio use, and i have no clue how to operate it what so ever. It was suggested i buy a pre-amp so i picked up a 2 channel tube pre amp… i connected the mic to the input and the output into my computer as well as into an amplifier and i still got ZERO sound what soever ….any ideas at all??

http://www.homestudiocorner.com Joe Gilder

Did you turn on phantom power?

Tinkerscuss

Hi. Just read your comments and so revisited my setup (Neumann TLM49 into Universal Audio Solo610 into Presonus Audiobox 44VSL interface) Used an XLR line out of the AU to a TRS line in on the presonus… Now! I was expecting miracles after reading your article, instead I lost about 70% of the volume and noticed no difference using XLR to XLR either. I also had to crank up the input gain on the 44VSL to get any sound at all. So what’s going on??

http://www.homestudiocorner.com Joe Gilder

Hard to say, Tinkerscuss. Sounds like you need more gain from the Solo610.

Yuber

Hi, I’m thinking on buying a Focusrite ISA One preamp and I’ve noticed it only has XLR outputs. Should I connect it to the XLR input of my interface or use an XLR-to-1/4 converter on my cable into the TRS input? Thanks!

http://www.homestudiocorner.com Joe Gilder

Depends on the interface, but as the article says, you probably want to go to the TRS line input on your interface.

Lottylee

Hi Joe,

I’m a newbie to this audio stuff. I read online and bought the DJ Pre II phono preamplifier. Thought this was going to be including cables and such. Oye. So anyhow, before I go any further, I would like some advice about the best ways to get my turntable thru this thing and into a computer. I have no fancy sound card yet. Just a couple regular CPU’s running Vista and XP. Just looking to get some of my rarer albums into mp3 or wav format.

http://www.homestudiocorner.com Joe Gilder

That’s not my expertise, sorry. Call Sweetwater. They’ll have somebody who will know the answer to your question. 800-222-4700 http://www.sweetwater.com

Joosoohan

Hi Joe,
I have a question.
I have a thought and please tell me if I am wrong.
Mic line (xlr) is mono and trs cable is a stereo line.
What goes into a mic pre is a mono therefore If I want to connect
my mic pre into a mixer, I should use TS (guitar cable which is mono)
cable into a mixer line. Is this method right?

http://www.homestudiocorner.com Joe Gilder

Nope. That’s not correct. TRS is mono. The cable used for headphones IS a TRS cable, but it’s actually carrying unbalanced left and right copies of the signal to the headphones. When talking about preamps and line level connections, TRS is always balanced mono.

Randalls

Hi I have a m audio fast track and a art tube pre. I currently connect iw with the mic going into the art pre via xlr and the xlr output into the fast track. Is this correct or should I use 1/4 to 1/4 connection

http://www.homestudiocorner.com Joe Gilder

You should probably use the 1/4″ inputs on the fast track. XLR inputs are for microphones only, as stated in the article.

Deedee

I bought the silver bullet for my flute with a preamp and am clueless about what I need to do to hook up to my computer or amplifier??

http://www.homestudiocorner.com Joe Gilder

Hey Deedee. Gonna need more information than that. Do you have a recording setup already? Do you have an audio interface that runs into your computer?

Adam

Hi Joe,
Nice post! I have a question I have been trying to figure out for some time and haven’t found an adequate resolution yet. I have a Presonus Studio Channel that I am using but I can’t seem to get it to work the way I’d like.

Setup:
I am sending a Shure SM27 into the Presonus Studio Channel and sending a TRS out and into the line input on my Presonus Firepod (now called the FP10). From there, I go to the input channel on my software (Cubase 6) and begin to adjust the input gain on the Studio Channel. When I set a level, I increase the input gain until the level is at about 75% on the input channel of my software. For some reason, when setting the level with the Studio Channel in my setup, I reach 0 on the VU of the Studio Channel way before it reaches 75% on the input level of my software. If I am recording vocals, this signal would be way too quiet unless I cranked it way up in the mix. Does this preamp just have really low output? Am I doing something wrong?

If you have any advice, I’d really appreciate it.

Thanks!

http://www.homestudiocorner.com Joe Gilder

I wouldn’t worry about the VU meter. Analog meters were meant to be pushed. As long as you’re not clipping into your software, you’re fine.
Honestly, as long as you’re happy with the sound I wouldn’t worry about little details like that.

Darren Marc

Hi, what’s the advantage of using an XLR to 1/4inch going from my mic pre to my audio interface vs. XLR to XLR? Currently I go XLR to XLR.

Also, I have three places to adjust the level:
1) mic pre gain
2) mic pre output level
3) audio interface gain
How do I go about adjusting all 3 to give me the best sound?

http://www.homestudiocorner.com Joe Gilder

There’s no advantage of 1/4″ over XLR. It’s exactly the same, just different ways of connecting.
I would leave the audio interface gain at unity (no gain), and then adjust the preamp to the desired level/sound.

biffbiffson

So, just to clarify, I’ve been checking the internet for hours and I haven’t really gotten a clear answer to my question:

So I’m using an Alesis MultiMix 8, which has 4 XLR inputs going through the preamp, and 4 line-inputs that don’t go through the preamp because they’re line-level. How can I use those line-levels to record microphones for when I need to record drums? I really need to know before I purchase a tube preamp, and my idea is just that the microphone goes to XLR cable to the preamp, then out of the preamp use a TRS cable into the balanced line-input, and that would be it.

Is this correct, or am I doing something wrong?

http://www.homestudiocorner.com Joe Gilder

Yep, that’s correct. However, I’m not sure you can record multiple tracks with the Alesis MultiMix 8. I think it only records the stereo mix of all the inputs on the mixer. You’ll want to check on that first.

Robin

hello,
im new with home recording
i have a sound card which is ESI Juli@ with 2xTS line(R&L) in & 2xTS Output
and behringer ultragain mic200

so here is what i do, i put the mic into line in on mic200, then i put the output from mic200 into my line in on ESI Juli@ which i only put in 1 slot either R or L

i have program to monitoring bundled from ESI and i can see there is a sound i can get from the monitoring which the metering are up and down when im testing the mic

but somehow, when i try to record through the record software by windows, there no sound at all
somemore i try to use the speaker to listen to the mic it self and i got no sound as well

fyi : im using windows7 64bit

do i did a mistake? or is there something wrong with my windows instead?

thx for ur time to read my problem

regard

http://www.homestudiocorner.com Joe Gilder

I’m sorry, Robin. I don’t really know. Never heard of ESI. You might want to call the company that makes it.