Improving Recording Quality

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This page explains the importance of reducing noise in all parts of the recording chain, and of upgrading sound card and microphone to achieve high quality recordings
The mentioning of equipment brands in this article is not meant as an endorsement, but rather represents the experience of the author(s).
 
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Contents

Your current system

The built-in sound card that comes with many computers is quite poor. It may be satisfactory for playing sound effects, but not good enough for high-quality recording. Often the worst ones are the built-in sound on your motherboard, or any audio device on a laptop. Note that you don't always get what you pay for: a $20 basic sound card could sound great, and a $100 sound card might have lots of problems. Some tips to reduce noise on your current system:

  • Mute playback of devices that you don't use for recording - such as MIDI Synth, CD Audio, TAD-In, Auxiliary, Microphone, Line In. Only "un-mute" devices to be used.
  • Ensure you update your sound drivers: Find the web site for your computer manufacturer or sound card manufacturer and see if they have a new driver for you to download (on Windows you can also try Device Manager first).
  • If possible, insert your soundcard into a PCI slot which has a dedicated "Interrupt Request (IRQ) Channel", as described in your motherboard handbook. Except for dual processor motherboards, there will probably be 4 electronic IRQ channels used to assign IRQs. (This is not the same thing as the 16 virtual IRQs we usually talk about.) For example, on my ASUS CUV4X mobo, Interrupt Request channel "A" is shared by AGP (reportedly noisier than PCI video cards) & PCI-slot1 (leave blank if AGP is in use) & PCI-slot5 (empty). Int-"B" is shared by AGP & PCI-slot2 (NIC - noisy). Int-"C" is a dedicated electronic channel, taking hardwire interrupt pulses generated solely by the device installed in PCI-slot3 (soundcard). Int-"D" is shared by PCI-slot4 (SCSI - noisy) and USB-controller (mouse, keyboard, etc. - very noisy). If I install my soundcard in any slot other than PCI-slot3, the result is a scratching sound, like a loose connection at an input jack. But, it comes from the mouse pulses (slot controlled by Int-"D") or from video rewrites (slot controlled by either int-"A" or "B").
  • Even if you are using a 'silent PC' (one with passive cooling rather than a fan) you will still need sound insulation between it and your mic (a piece of felted board will do) as the hard drives are not silent.
  • If you are using any outboard (externally powered) audio hardware, make sure all the equipment is plugged into the same power strip. Grounding issues can cause ground loops, which will appear in your recording as a hum. For more info, see Reducing noise.


Equipment upgrades

Cheap sound hardware, anywhere in the analog chain, will result in poor quality recorded sound. Consider upgrading your audio hardware!

Sound cards

Buy a new sound card - especially if you were using your computer's built-in audio capabilities before. The sound card's ADC or analog > digital converter is the final step in your analog audio chain. Consider buying a USB audio device such as the external interfaces made by M-Audio or Edirol. The main advantage is that the A/D converter is then outside your computer's case, which keeps electrical noise to a minimum - only the digital signal gets transmitted back to your computer. Another advantage is that you don't have to open up your computer to install anything, just plug it in and go (after installing any software drivers required by the device). It's easier to share it between multiple computers, too. Make sure other USB devices are unplugged if not being used, as especially USB 1.x has a limited bandwidth. Even things like network cards can interfere with USB audio so disable them. Some specific recommendations:

  • M-Audio Duo - this puts most sound cards to shame and can be had on eBay for a couple of hundred dollars
  • Behringer UCA 202 and Griffin iMic (both Linux-compatible), or devices by Edirol and Tascam - for details, see this Forum thread.

Microphones

Microphones, more than any other single piece of hardware, will impact the quality of your recorded sound. This is one area that you indeed get what you pay for. Professional microphones can be had for $40 and up (way up).

  • If you're just getting started in home recording, you can't go far wrong with products from Shure. Models SM58 and SM57 are workhorse microphones of the professional audio world, and as long as you don't mistreat them terribly their resale value holds up quite well. Like all pro microphones, Shures will need their signal to be boosted before it is suitable for input into a computer. They recommend bypassing the computer sound card and connecting the microphone to the computer via a USB adaptor such as the Shure X2u XLR-to-USB - this is a good Linux-compatible product. If using other solutions such as pre-amplifiers or transformers, Shure recommends reading this detailed article to understand the finer points of wiring and voltages.
  • If you are doing studio work, a condenser microphone (rather than a dynamic) will probably be the most suitable. They have greater accuracy and dynamic and transient response compared to dynamic microphones. For live recordings, professional dynamic microphones may be preferable - they will be less prone to picking up extraneous stage and audience noise. For a technical explanation of the difference between condenser and dynamic microphones, and of the different types of polar patterns such as cardioid that microphones use, see this Wikipedia article.
  • If you use a professional microphone, you'll need a good preamp. The "mic" input on a sound card has a preamp behind it, but it's usually not very good quality and will usually not provide sufficient amplification for the low outputs of pro microphones. Consider using a mixer board with microphone and line inputs (useful for electric guitars and keyboards) and a line output that you can connect to the line input of your sound card. Behringer makes quality low-end mixing boards that are a good starting point for beginning home recordists. The UB802 (now discontinued) was an excellent entry-level unit with a street price well under $100, and can now be found online for about half that price.
  • Note also that built-in computer 1/4 inch mic ports are almost always mono and unbalanced. Built-in computer line-in ports are almost always unbalanced. Unbalanced inputs mean you must keep the cable short to prevent interference and muffling, but this increases the interference risk from being too close to the computer. For this reason, many external USB and firewire recording interfaces will provide balanced inputs and outputs.
  • Don't forget accessories like microphone stands and cables. Decent stands and some cables can be had from Radio Shack, but these cables will likely start to hum and buzz after a year or two. Professional microphones use XLR cables that you might be better off getting from a store that caters to audio professionals. For a sure bet, you could choose Digiflex Tourflex cables. These wires are a bit more expensive, but connections wont get loose, and if they do, the cables are guaranteed 10 years.


Microphone techniques and problems

Don't forget to learn good microphone technique (or the hardware will be wasted); and to read up further if you are new to recording.

  • Always record slightly above/below or to the side of any microphone
  • Use a pop filter
  • The internet has plenty of further reading on microphone techniques and common problems. For example, try:
Microphone techniques
Microphone FAQs
Signal problems
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