It wasn’t that long ago – maybe 15 or 20 years at most –when a quality studio incorporating all of the technologies that have revolutionized recorded music over the decades would have cost tens of thousands of dollars. But now, anyone can produce a good quality recording on a simple home computer with a few hundred dollars worth of software. Better still, the Internet has provided a free channel for global music distribution – an opportunity well beyond the reach of the singer-songwriter or garage ban of yesteryear.
“…the computer music market went from just under $140 million in sales in 1999 to almost a half-billion dollars in 2008.”
Consider this: According to the Los Angeles Times, over half the commercial recording studios in the L.A. area had closed or been sold to artists for private use. And NAMM, the trade association for music manufacturers, reported that the computer music market went from just under $140 million in sales in 1999 to almost a half-billion dollars in 2008. Recording software like Avid Technology Inc.’s Pro Tools, Steinberg Media Technologies’ Cubase and Apple Inc.’s Garage Band perform many of the tasks of old-school studio consoles and tape recorders at a fraction of the price.
Carr puts it this way: “Some people call it the triumph of the amateurs — the ultimate democratization of the means of production. Others say it’s the end of pop music as we know it.1”
Most Shure customers agree with the former and not the latter. That’s why “How do I connect a microphone to a sound card?” has held a top ten position question among 3, 658 questions in shure.com’s Technical FAQ (Find an Answer) section since 2002.
In this post, we turned to Shure Associate Gabe Benitez for an overview of the basics. First, we’ll cover some fundamental concepts. Then, we’ll move on to considerations when using an XLR-to-USB adapter.
The growing popularity of home studio recording consistently raises the question of interfacing professional microphones with computer sound cards. Unfortunately, sound cards are rarely designed for professional microphone use. They often provide poor, low level and noisy sound that doesn’t match the quality of the recording package or the mic. The good news is that properly interfacing a mic to a sound card isn’t that difficult.
In order to interface a microphone to any device, we have to consider the electrical and mechanical compatibility between them. Here’s what that means:
This is the actual voltage that comes out of a source or is needed by a receiving device, for example a sound card. Professional microphones put out a very low voltage in the range of 1 millivolt (1/1000th of a volt). Sound cards on the other hand require levels in the order of 10 millivolts (ten times as much!). So the first step is to increase the level before we get to the sound card.
This is similar to resistance and its vital when interfacing two circuits. The relationship between the source impedance (microphone) and the load impedance (sound card) will determine how much of the energy coming from the mic is actually transferred to the sound card. Load impedance should be around ten times the source impedance. Professional microphones usually have between 150-600 Ohms. Soundcards have between 600-2000 Ohms. In most cases impedance will not be problematic.
Connector and wiring scheme
This is probably the most visible of the problems. There are more than a few connector types in the audio industry. Professional microphones use XLR connectors. Sound cards, due to space constraints, are equipped with a smaller connector, usually a 3.5mm “miniplug”. Although these look the same from the outside, there are at least three different types and multiple wiring schemes. Unfortunately, there is no standard for sound cards. Some are balanced, others are stereo, and others provide bias in separate wires. On most sound cards there is a line input next to the mic input that has the same connector. The line input is far more standardized than the mic input. This, as it will be explained later, will let us properly connect a microphone to the sound card.
Dynamic vs. Condenser
Connecting a condenser mic to a sound card requires power, while a dynamic does not. Although sound cards can provide bias, they will not provide or have the capability to supply the phantom power that is needed for condenser mics. If you want to use a studio-grade condenser microphone, you will need an external power supply.
This may all seem a little daunting, but there’s a simple way to connect just about any microphone to a sound card and that’s by using an external microphone preamplifier that has a line and/or a USB output. If you use the line output, connect it to the line input of the sound card. If the preamplifier has a USB output, even better – avoid the sound card and go directly to the computer through the USB port. These preamplifiers come in different shapes, forms and prices (with some as low as $40) and many will let you connect a dynamic or condenser microphone (if they provide phantom power) and gives you the ability to get the professional sound that you would expect from your Shure microphone.