Pro Audio on a Laptop
Thursday, April 16th, 2009Recently I wanted to record some nature sounds using my laptop (I live on a lake, and the frogs are out). Since there’s a road nearby, I wanted a directional microphone so I wouldn’t pick up incidental noises as cars went by. This meant I needed either a unidirectional or cardioid mike — the former picks up noise from one direction only, while the other has a heart-shaped (hence ‘cardioid’) pickup pattern.
Every generic laptop mike I checked was omidirectional, so I went to a local audio store and picked up a decent semi-pro grade unit for about $40. It used a standard 1/4″ jack, so I snagged an adapter that reduced it to the 1/8″ jack found on all laptops. Then I headed to the lake and tried recording. Absolutely nothing came through, so I tried the same unit on my desktop machine. Still no results. Some additional research was obviously in order.
It turns out larger (usually condenser-style) mikes only put out about 1/1000 of a volt, which is too low for audio cards to pick up. You need a preamplifier between the mike and audio card to boost the signal to the level achieved by cheap PC-style microphones, which have a much higher output level. But adding a preamp to the mix meant lugging a piece of equipment that needs 110V line power out to the lake, which was not what I wanted to do.
There are several options. In some cases pro-grade mikes can use what’s known as “phantom power,” which is a 48V input. You can buy “phantom power” adapters from audio stores. These accept input from a pro-grade mike and boost the output to a level acceptable to a PC audio system. Only certain mikes can deal with phantom power, so don’t hook one of these adapters to your mike without making sure it can handle the 48V input. Otherwise you’ll probably ruin the mike.
The other option is a USB-based preamp. I found a $44 Blue Microphones Icicle unit that adapts directly from the pro mike’s 1/4″ jack to the USB on my laptop, and which claims to require no special drivers.
The unit hasn’t arrived yet, but should be here Monday. If it works as advertised, I’ll be able to record decent quality audio, albeit in mono mode only. Stereo would be a totally different matter, I suspect. So if you’ve ever wondered why you can’t use your studio condenser mike directly with your PC, now you know.