Continued from: Mixing Digitally - Adding Warmth to Clarity (Part 1 - Background)

The first and most logical step to adding warmth to Digital recordings is to use nice analog gear before the A/D converter in the recording chain. Using mic-pres and tube gear can be great ways to introduce some warmth and color to the signal when recording. Always keep in mind though that any color you add at this point is printed and cannot be removed (at least not easily). Recording through a SSL channel strip (or the whole console if you’ve got one) can produce some very nice results.

You might be saying “Well come on Ian, not everyone has a SSL to record through.” You’re right, so here’s the plan. Most of us only have whatever pre-amps our sound card came with and typically the plug-ins that came with our application. We need to create a system to put the same distortion or color into our mixes as the analog gear of yesterday.

Step 1: Get a sense of how the old gear and your favorite recordings sound. Are the mixes bright, or punchy, how do the drums sound, what kinds of effects were used? It’s always easier to get the sound you want when you know what the sound you want sounds like :).

Step 2: Setup a virtual mix bus. As you do more and more mixing you should get a feel for how you like your master bus to sound. As this becomes clear try to establish some consistency. Just like using an analog mix bus that has the same circuitry for every mix so should your digital mix bus. Do this first before you set mix levels or anything. Come up with a set of plug-ins that will be your custom mix bus and and mix the entire time through them. McDSP makes some excellent plug-ins for this but look for plug-ins that have channel characteristics (i.e. EQ and Dynamics). Avoid multi-band compressors at this point though; leave that for the mastering stages. For example, my mix bus on my Pro Tools LE system at home always has a McDSP “Analog Channel” and a P4 equalizer.

*Note: If possible, don’t stereo link the plug-ins on the mix bus and tweak the settings on each just by the littlest bit so they don’t match exactly. This can create a more natural sounding stereo image. (Remember on an analog console no two channel paths are exactly the same due to the manufacturing tolerances of electrical components.)

Step 3: If you have the DSP power, extend this principal to each individual track applying EQ and Dynamics to each channel as if you were using the inline modules of a real mixing console. This is also where I would encourage you to apply the “Tape Saturation” or “Tube warming” plug-ins if you’ve got them. Remember to use these effects for subtle coloration of the sound. If you’ve got the power, I like to EQ before and after the Saturation and/or warming plug-ins. Remember, we are emulating the analog signal flow back from a real tape machine.

Step 4: This may or may not be considered a warmth issue but it does kind of apply as far as emulating outboard signal flow with plug-ins. When using sends for effects like reverb (you are using sends or aux’s right :)), if possible, EQ the send for certain signals. Don’t send too much top end (cymbals) to the reverb as this can produce a very splashy sound in high frequencies. Don’t send too much of the bottom end either as this can very quickly muddy up your mix. It’s typically best to band pass your reverb sends and if get really creative you can EQ all your reverb signals so that they sit well together. Often Outboard gear, because of cable runs, inherently had some bandpass filtering and many times the circuitry would limit the frequency spectrum, as well.

Using this setup will also force you to use the same plug-ins consistently thus give you a firm understanding of their use. This will make you much more efficient as an engineer and give you the confidence that you know how to achieve the sound you are looking (listening) for.

When mixing digitally, which is often the case in a home recording studio, there are a few things that you can do to get your mixes to sound like the great mixes of the good ol’ days (when everything was analog). Before we can explore the options of warming up your mix it’s essential to understand how digital and analog mixing differ.

The first step to understanding the difference is to define actually what is “analog warmth”? Sound has always been one of the hardest things to describe in words, and warmth can be interpreted in numerous ways, but I believe that the following description is what most people are talking about when describing “a warm sound”.

At the most basic level, warmth is distortion. We call it distortion because warmth actually changes the waveform of the sound, thus distorting it from the actual natural waveform. Warmth or color is a particular type of distortion that happens naturally inside analog gear. When sound waves are converted to electrical waves using a transducer (microphone, generally in the audio engineering realm) it is never a perfect replication. This is what spurns frequency response curves, and why a condenser microphones sound significantly different to dynamic microphones, and why Neumanns sound different than SM58s.
So microphone circuitry is the first stage of analog warmth. Historically, certain microphone types have become very famous because of the desirable and enjoyable warmth or color they add to a sound signal.

The next stage is the mic pre-amp. This is often a critical part of the chain as it is the first time the engineer has control over the signal (aside from mic choice and placement). It is always part of the recording chain (meaning that once you record it, it cannot be undone). This is why people will spend big dollars on a mic-pre that suits their taste and style. Since many people tend to like tube or valve mic-pres now would be a good time to talk about tubes.

Tubes (specifically triodes) are often used in pre-amps, in mic-pres, guitar amps, bass amps, even some mixing consoles use tubes in their circuitry. This is because tubes have a distortion characteristic that is very pleasing to the ear. Simply, when a tube distorts the distortion manifests itself primarily in the second and third harmonics of the fundamental frequency. That is, if the note of the sound entering the circuitry is an E the distortion created around that sound will primarily sound like an E an octave above, and a B above that (so the distortion is primarily an octave and an octave plus a fifth, both of which are consonances with the fundamental). OK, so maybe that wasn’t so simple, how about this: the distortion from tubes sounds good with the original signal.

BJTs and MOSFETs, generally called “solid state” are not quite as nice when they distort. The distortion created by these devices typically resides in third and higher odd fundamentals (5, 7, 9…). Musically this is not as desirable. The distortion in the third harmonic (an octave plus a fifth) is often considered a consonance, but the higher order odd harmonics are not considered consonant, and therefore add tension to the signal. This tension is often described as “harsh” or “gritty.” The advantage of solid-state circuitry is that it is considered “cleaner” when it is not pushed into distortion. Cleaner, meaning less intrusive upon the original signal; a more accurate representation of the original sound (which also means less color).

Herein lies our issue as audio engineers. We now have the most accurate signal path to record through that the world has ever seen and the best part about it is that it is substantially cheaper to produce than the old electronics. This is all well and good except it is generally agreed upon that the old stuff “sounded better”. Now “better” may just mean we are more used to it; familiar with it, like comfort food. With the background of the problem acknowledged, let’s address the issue of how to add the analog warmth back into our digital mixes for the best of both worlds. (Please See Mixing Digitally: Adding Warmth to Clarity (Part 2: Practical Applications))