Signal Processors Explained
By Max on Apr 3, 2008 in Home Recording
Signal processors can be anything that changes the sound of an audio signal in some way. This differs from an effects processor which generally adds something to the audio signal, not something that tailors it the way a signal processor does.
Since the term “signal processor” is a general term for many different devices, so it could be a Filter, an EQ, a Compressor, a Gate, an Expander, a Limiter, a Transient processor, a Preamp, a DeEsser, a Stereo Spreader/Imager, and many other things. Lets start by going down the list.
Filters
A Filter is a device that cuts out a specific amount of the audio signal. The usual types you will see are High Pass (meaning it will cut out all the higher frequencies), Low Pass (meaning it will cut out all the lower frequencies/bass), and Band Pass (cuts out a specified frequency).
There are many other types but these are the ones that will concern a home recorder most. For a decent filter I would suggest looking at the Electrix Filter Queen or Factory (depending on budget) as these offer incredible results for their worth.
EQ’s
An EQ is a device that boosts or drops one or many frequencies in the audio signal. The easiest way to think of an EQ is to visualize a bunch of filters tied together. The main types of EQ’s you will see are 3 to 4 band Parametric EQ’s which offer a Hi band, Hi-Mid band, and Low band. Parametric EQ’s are not perfect, though. When you adjust the Hi band you will be adjusting part of the Hi-Mid as well because of a slope that binds each band together.
Graphical EQ’s
Next are Graphical EQ’s. These offer many more bands of EQ’s which makes it easier to select and adjust a specific frequency versus a wide spectrum of the signal. Most commonly you will find these in studios and on stage in a 31 band version.
When it comes to Mastering an album you will generally want a parametric EQ that offers multiphase and octave support to keep the smaller frequencies from being left behind or buried. These small frequencies are subtle but necessary.
As for a Parametric EQ, I would suggest an PreSonus EQ3B and for a Graphic EQ I would suggest the Behringer Ultragraph.
Compressors
A Compressor is a device that takes an audio signal and tries to keep the volume within a specified range. These are insanely important in any recording as they help reduce noise, keep a sound from fluctuating in and out (unless desired), and prevent sounds from clipping. It is good practice to run everything through a compressor when recording. The main features to look for in a compressor is the Attack, Release, and Output.
There are also different types of compressors. The main three are Optical, Transistor, and Tube. Everyone will have a different view as to which is better, but it should be noted that what works for one track might not work for another.
Transistor type compressors are often found at the budget end of the spectrum as they are a lot easier to work with and cheaper to make. You will however see them in higher end products as well.
Optical compressors tend to be more of a hi-mid product as they are a more difficult and complex circuit to make, but do offer a lot better specs and more true sound. Tubes (or Valves in Europe) are a very passionate thing to most engineers as they generally add a “colour” to a sound, but also have a tendency to be noisier.
Overall I like units that offer both Tube and Optical as this can give you a choice in the matter depending on the track you are working on. Try looking at the Art Pro Channel.
Gates
A Gate is a great little tool that cuts any sound out that isn’t up to a specified level. This helps get rid of a lot of line noise in a track including outside disturbances. These can normally be found built into other units like Compressors and Preamps so I wont tell you which unit to look for specifically.
Limiters
A limiter is another great tool to has as it keeps all the sound, within a threshold, at a certain level. This differs from a compressor in that a Limiter can be adjusted by frequency not just total output volume. If you are looking for one, as they greatly help in final mixing, try the Waves Plugins as their L1 is probably the best one I’ve used.
Transient Processors
Transient Processors take those little bits of the signal that we might be able to hear noticeably and alter them to help shape the overall sound but these units are expensive. The SPL Transient Designer 4 is $1,250 alone.
Preamps
The gist of a Preamp is that they are used to bring things like guitars and microphones up to a manageable level before mixing. You find the same debates in these as you do in Compressors, just with a few different components. You have Tubes again, Transistors, and Transformers.
There is no ultimate preamp as everyone has a different taste and sound. The big things to look for is the amount of gain (somewhere in the 60+dB range to start) and how much noise it puts out.
What I would recommend for anyone starting out is to look into Channel Strips and these offer a Preamp, Compressor/Limiter, and EQ in one package. Many times you wont get the same quality as if you bought each piece alone, but they are great for having everything in one spot. Again I would recommend looking into the Art Pro Channel.
Stereo Spreaders
A Stereo Spreader is a piece of equipment that helps widen the stereo field so that the sound seems bigger and fuller. These are generally pretty basic looking things that offer very few control, such as “width.” The best one I’ve used is the built in “Stereo Spread” from Steinberg’s Nuendo 2, though it might be on other versions as well.
Stereo Imagers
A Stereo Imager is a piece of equipment that takes a mono signal, such as a microphone, and doubles it into a stereo signal. These are great for helping you give some width to that vocal tracks. Again here I’d have to suggest looking into the Waves Plugins as they have the best and easiest one in a plugin form.
Pretty much any software will do this though so there is no real need to get the plugin, also if you are going through a mixer before the recorder it is doing this as well.
I hope this information about processors was helpful and that you check in again for more great Home Recording articles.
