Can I boost the line-in feed on my laptop?

February 7, 2006 4:17 PM

PC Audio: How can I boost the audio coming in through my laptop's line-in?

I'm recording classes using a single boundary microphone connected to my laptop. On playback, the speaker is audible and intelligible, but I have to max out my volume controls and questioners can't be heard.

Is there a way, on my laptop, to boost the line-in signal? I have maxed out the mic volume control, and I don't seem to have any kind of Mic Boost or AGC function on my soundcard. (A SOUNDMAX Digital Audio, if that matters)

I have a feeling the "correct" solution here is to get a microphone preamp, but those that I have seen on the interweb are pricey ($200 and up), and my classes just aren't worth it. I'm seeking a cheaper alternative.

posted by Brian James to Technology (17 answers total)

Sounds like your looking for a mic with phantom power - i.e. a 9volt battery or AA inside the mic. Radio shack? Make sure to turn on and check the advanced prefs in the volume menu b/c there might be something for the mic to boost its DB as well. Audacity (free great audio app) lets you normalize and then remove silence noise, but it can get weird if theres too much stuff to silence
posted by psychobum at 4:27 PM on February 7, 2006

The answer is to get the cheapest external sound card you can find with a mic input.

As to preamps being expensive, there are decent and cheap ones: M-Audio's Audio Buddy goes for about $80. (You can find awful ones for even less.) MobilePre USB (~$130) is the same built into an interface (basically a fancy word for sound card).
posted by abcde at 4:45 PM on February 7, 2006

Actually, Psychobum, that's not Phantom Power as such.

Brian - the reason the level recorded by your laptop is so low is that the signal from the microphone is at a very low level, and is expected to be amplified at some point along the chain.

Some minidisc recorders offer "plug-in power" - i.e. the recorder powers the microphone - but I'm not aware of this being common with laptops.

What can you tell us about the microphone you're using? Does it have a battery compartment on it somewhere? What kind of connector does your mic have? I'm presuming it's a 3.5mm (mini)jack? Sounds to me like it's expecting plug-in power.
posted by coach_mcguirk at 4:45 PM on February 7, 2006

(Actually, doesn't particularly have to be external; don't know why I said that.)
posted by abcde at 4:47 PM on February 7, 2006

To be clear, though, you just want a sound card. The $90 or so Creative Audigy 2 ZS Notebook would be more than enough.
posted by abcde at 4:57 PM on February 7, 2006

Sorry to spam, but I'll sell you my mobile pre usb box for $50ish. I want the one without pre-amps instead (for recording line level stuff).

Also, sony has quite a few decent mics for $50-$100 that they've had around since the introduction of their MD players a while back. I think a lot of them start with ECM in the product name
posted by p3t3 at 5:06 PM on February 7, 2006

Another cheap USB audio device is the Griffin iMic (about US$30). Just plug the iMic into your computer's USB port, and plug the microphone into the iMic. There's a small switch on the iMic to tell it whether to treat the input as line-level or mic-level.
posted by mbrubeck at 5:09 PM on February 7, 2006

Response by poster: Thanks for the responses so far.

This is the mic I am using. The S/N is very good for the price. It does have a small watch battery compartment, but I don't think the battery is used to amplify the signal.

Would something like this do me any good? I'm thinking maybe the drivers for the USB device might allow for some mic boost-type function that my built-in sound card doesn't have.

The Creative device abcde posted looks pretty sweet...
posted by Brian James at 5:56 PM on February 7, 2006

before you break down and buy anything though make sure to look for options - advanced controls on the volume control menu. there might be an option to boost the mic on the advanced mic properties, there is on my laptop with the same soundMAX thing. If you do have to buy something consider nicer stuff, its cheaper in the long run if you plan on making a lot of audio. I have an mxl-drk mic going into an m-audio firewire solo and its quite an improvement over the laptop. My laptop mic in sounds very poor, theres some background fuzz, even if im using the nice mic.
posted by psychobum at 6:03 PM on February 7, 2006

That little USB thing isn't a major brand or anything, I don't see a particular reason to trust it. The levels will be fine, since after all it has a mic input, but the quality might be awful. Better off getting something mainstream.
posted by abcde at 9:18 PM on February 7, 2006

The mic is an electret, which doesn't need phantom power. The battery powers the impedance-matching amplifier, but that doesn't boost the output level, so you still need plenty of gain to boost the signal up to line level.

I second the advice to get a cheap sound card with a mic input or find (possibly used) a mic-to-USB dingus. Sound Devices make a good one, but it isn't all that cheap. I'm not that familiar with any others.
posted by the duck by the oboe at 10:35 PM on February 7, 2006

The answer is as you've been given already - you need a mic pre-amp of some description.

There are (in [very] general terms) three audio input levels: mic, line and instrument (often called hi-z). Of these, the lowest is mic - microphones produce very weak signals indeed and they always need to be amplified to be useful. A mic-input on a soundcard is merely an input with a built-in mic pre-amp.

The USB device you linked to is unlikely to have a pre-amp due to its size - most likely the USB drivers digially amplify the incoming signal using some normalisation process - this is almost guaranteed to give you exceedingly noisy results - I'd skip that option.

It's also worth checking you're getting the best out of your boundary/pz microphone - if you're not aware, these don't work like normal microphones. The pick-up for a pzm is underneath the plate, not on top of the mic where the cable enters. This should be placed squarely and firmly on a surface which will vibrate, which, in effect, becomes a part of the microphone. Commonly, pzm are placed on a wall or ceiling in conferences rooms as a secondary microphone rather than the main mic, and while I have often seen them placed straight on the desk between two people, this is not how they work well. If the budget is there, you might want to look at getting an omnidirectional microphone to place on the desk and use the pzm's on the walls.
posted by benzo8 at 11:24 PM on February 7, 2006

A mic preamp is the answer, but they are not all that expensive. I use the Audio Buddy from M-Audio. It's about $100. Spend another $60-$100 on a microphone and you're done. If people are walking up to a mic or passing one around, you can use something like a Sure SM-57 or an SM-58. Those are great mics, but they--by design, like all dynamic mics--only pick up things at very close range. If you need to grab the entire room, then you'll need some sort of condensor mic, which will pick up the loudest sound at any given moment.
posted by wheat at 6:36 AM on February 8, 2006

Sorry, but what wheat says about dynamics vs. condensors is not right - although in general condensors are more sensitive than dynamics, both would be perfectly capable of picking up conversations in a room. The issue is no sensitivity but pick-up pattern. Most common dynamics (including the two Shures that wheat mentioned) are cardoid in pattern, which means that they pick-up sounds better from in front of them (in the direction that the microphone is pointing) and less so sounds behind them. An omnidirectional microphone - either a dynamic or a condensor - will pick up sounds from all around itself equally well. A boundary/pz mic is omnidirectional.
posted by benzo8 at 7:55 AM on February 8, 2006

Thanks for the correction/clarification, benzo8. I guess, in my experience with it, 57's and 58's (directional/cardoid) where what you reached for when you wanted to close mic something or capture a single speaker and omnidirectional condensor mics where what you reached for when you wanted to get the ambiance of a room or something else that defies close micing.
posted by wheat at 10:36 AM on February 8, 2006

Just get a Samson USB mic (preferably the one with multiple patterns and set it to "omni"). Be done with it.

In my world, Samson is crap. But I have $5K worth of audio gear hanging off my laptop.

For your particular application, a Samson would probably be the best/most cost effective choice.

And use Audacity or Kristal Audio Engine to record (both are free).
posted by roguescout at 3:11 AM on February 19, 2006

I see plenty of savvy music techs have covered all the bases here. Or have they? How bout attaching the mic to a long telescoping rod which you can then pivot from source to source?
posted by bullnipple at 5:08 AM on August 13, 2006