Lesson 19

The Recording Chain

When I talk about sound quality, I’m talking about staying true to the original source. There are times when you want to add dirt, and that can be done intentionally and with control, but in order to do that with control, we need to be know how to get a clean sound. what I’m getting at here is all the intentional loss of fidelity that happens within the recording chain from the source, to the recording medium, and back to the listener.

1- source. Wether it’s an instrument or human voice, this is the sound we want to replicate. The quality of the source, being a skilled musician, a nice sounding instrument, and an overall good song, is probably the single greatest factor in having a great recording, but the purpose of this lesson is capturing the source, in whatever glory or misery it is, with as much fidelity as possible and knowing where the links of the chain are that cause a loss in fidelity.

2- room. Once the sound leaves the source, it bounces around and accumulates in the room. The microphone doesn’t know the difference, it just picks up everything, so the room will distort and change the sound.

3- microphone. Well this one is kinda obvious, but better microphones will capture the sound with greater authenticity. it’s usually more noticeable in the high frequencies, as a bad microphone will pick up the high frequencies as just white noise, and the better microphones will pick up the high frequencies for the sounds that they really are.

4- preamp. The microphone output is very low power, so before it can get converted to digital which the computer recognizes, it needs to be boosted. That’s what the preamp does. The preamp will have usually 2 or more stages of boosting the volume, called gain stages. The way a gain stage works, is kinda like taking a picture of a picture with a higher megapixel camera. The source sound actually gets discarded, but first it is replicated at a higher voltage. How accurate this replication is will affect the sound quality. Also, since an amplification circuit runs on dc voltage, and it is ac power coming from the wall plugin, it is the power supply that converts it to dc. The quality of this power supply also makes a big difference in how good the preamp will sound.

5- conversion. The conversion is the electronic circuit that changes the analog electrical signal from the preamp, into 0’s and 1’s that the computer can process. That’s called analog to digital conversion. And then, the digital to analog conversion takes the 0’s and 1’s from the computer, and converts them into an analog electrical signal which can then go to the speakers. I go into more detail about conversion in lesson 1.13, but for now, let’s just say the accuracy of the conversion will affect the sound quality. To be honest though, the quality of converters even in budget gear is very high, and does not really pose a significant loss in sound quality.

6- summing. This step is often overlooked, but plays a significant role in retaining clean sound. The summing is the mechanism which blends multiple tracks together into a single output. This can be done on a computer, or with a mixer. Either way there’s a loss of sound quality, because the computer is limited to the bit depth and algorithm, and the analog mixer is limited to all the gain stages and other components. I go into more detail about this in lesson 4.12, in the box and out of the box summing.

7- speakers. The speakers are broken up into 2 parts, there’s the amplifier which receives the weak output from the converters, and amplifies it to high power to drive the speakers. The quality of the amplifier will effect how accurately the gets amplified. then there’s the speakers themselves. The actual speaker will be limited to how precise it can replicate the incoming electrical wave, and the design of the speaker enclosure will effect how accurately that wave is transferred into air pressure changes. Also, if there is more than one speaker, such as a 2 way speaker that has a tweeter and a woofer, there is a crossover circuit which sends the right frequencies to the right speaker. Of course, the quality and the tuning of this circuit will effect how good the speakers sound. 
Another part of speaker design is having a bass port. This is a hole in the speaker which naturally amplified the bass. A port will always be detrimental to the integrity of the sound, but because it makes the bass louder, it is often a desirable compromise.

8- the room, again. Unless you are listening with headphones, your room, or car environment will have reflections and impart its own sonic qualities on the sound that enters your ear.

I’ve numbered these links in the chain from 1-8. If I were to list these in order of importance, as in what effects the sound quality from most to least, numbers 1-4 would remain the same. So, the most important factors are
1 source
2- room acoustics
3- microphone
4- preamp.

and the others are pretty much even, except I’d probably put conversion last.