In a time before computers and Pro Tools, every recording studio was lined with racks of meters, knobs, and glowing lights. This outboard equipment allowed the engineer to alter sounds. Each unit had a specific function such as gain, EQ, compression, distortion, reverb, delay, etc. The recording engineer would route signals through multiple devices to create the desired effect.
The emergence of digital audio workstations allowed all of this processing to happen inside the computer. Signal processing is essentially just math. For example, compression follows an equation based on the original sound wave and any parameters that are changed on the device.
Theoretically, a sound run through a compressor with the same settings will always create the same result. Well, “theoretically” only exists in the world of computers. In analog equipment with tubes and transistors, there is a certain amount of natural imperfection. These imperfections are what give analog equipment their “character”. High-end digital plug-ins are based on the original equations but have programmed variations to emulate analog character.
Outboard equipment can be up to ten times the cost of the relative plug-in. As we build our studios with limited budgets, we need to decide what outboard gear has the most value. Some digital plug-ins such as reverb or delay perform just as well as their outboard counterparts. In my experience, gain, compression, and EQ see the greatest sonic benefit from analog processing. Let’s discuss a few options of outboard gear in these categories.
Preamps
There is a mentality of “fixing it in post”: If it doesn’t sound right when you record it you can always edit it later. This is not the best idea. High-end recordings focus on making the sounds as pleasing as possible before they are ever recorded. This leaves minimal edits and sounds that are more full and alive. Recording a great sound starts with the analog preamp. The preamp adds gain (level) to the original sound. In addition to volume, analog preamps add character and warmth.
Universal Audio Solo 610 ($999.00): had nearly the same internal design since the 1950’s. This silky and warm vintage preamp can be heard on countless records from the last 50 years. The single channel 610 features all-tube preamp circuitry with gain, level, and impedance selection for maximum tonal variety. The American-made 610 has inputs and outputs for XLR and 1/4″ as well as DI features like thru, ground lift, and line/mic output switch.
DBX 386 Dual Vacuum Tube Preamp ($529.95): a more affordable tube preamp with two channels. Two channels means it is essentially two preamps – double the value. You can process two mono signals or one stereo signal. The DBX 386 provides 60dB of gain and +/- 15 dB of output gain. The device also offers selectable mic/line switch, 48v phantom power, 20dB pad, 75Hz low cut filter, and a phase reverse. In addition, this modern piece of gear also has digital connectivity and can function as its own stand-alone two-channel A/D converter.
EQ
EQ’s or equalizers allow the engineer to add or subtract volume in specific frequency ranges such as low, mid, and high. EQ gives the engineer the power to shape and blend the timbre of sounds so that they fit well in the mix as well as please our ears.
Manley Labs Massive Passive EQ ($5,040): often emulated as a digital plug-in because of its powerful passive EQ, warm tubes, and minimal coloration. The Massive is a fully passive, two-channel, four band equalizer, with additional high pass and low pass filters. The make-up gain amplifiers are all-tube to create thick analog sounds with plenty of headroom. Manley’s tube stages handle huge HF boosts without sibilance and unbelievable fatness without mud. The Massive can be used for subtle shadings of a vocal or for radical EQ’s to spark your creativity.
Compressors
Compressors are used to reduce the volume of loud sounds or amplify quiet sounds in order to narrow or “compress” an audio signal’s dynamic range. By changing the parameters, the user can explore a wide variety of compression from a single unit. These parameters include: threshold (the volume at which the compressor activates), ratio (the amount of gain reduction), attack and release (how fast the compressor reacts), as well as other parameters.
Universal Audio 1176LN ($1,999): another classic design from UA. This analog design has not changed much over the decades and can be found in most professional studios. The 1176 utilizes transistors (F.E.T.) as opposed to tubes in order to have faster action and superior performance. The 1176 offers compression ratios of 4:1, 8:1, 12:1, and 20:1. The device has fully adjustable attack, release, input, and output. The single channel 1176 features a class A line-level output amplifier as well as a custom-built output transformer.
Manley Stereo Variable MU Compressor ($3,960): a favorite of producers and recording engineers. Its adjustable attack and release settings are optimized for mixing and 
mastering, but are flexible for most tracking situations. Designed with a similar limiting principle as the legendary Fairchild 670, the MU uses tubes to smoothly change gain. The MU includes HP sidechain, variable attack, separate limit or compress mode, and fully differential all-tube circuitry. While designed for stereo signals it can be used on mono as well. The Manley MU is a great way to take “in the box” mixes out of the box and add a layer of analog flavor on top.
Combo Units
In an attempt to save studio space as well as cost, combo units have become popular. These devices perform multiple analog functions (preamp, EQ, compression) within one chassis.
Universal Audio 6176 ($2,499): combines the 610 preamp and the 1176 compressor into one single channel unit. The preamp can run directly into the compressor in join mode for a classic analog signal path. In split mode the preamp and compressor can handle separate signals. The 6176 mic preamp maintains the quality and character of the 610 while adding high-tension power regulation for improved bass response and a front-panel 15dB pad switch. The preamp also has high and low frequency shelving with three different frequency options for each. This allows the 610 to have some EQ capabilities for timbre shaping. The compressor stage of the 6176 is identical to what can be found in the 1176LN.
Universal Audio LA-610 Mkii ($1,599): combines the 610 preamp and the LA-2A compressor. The preamp in this device is the same as the one featured in the 6176. The LA-2A uses an electro-optical detector to create warm natural-sounding compression. The LA-2A has less controllable parameters than the 1176, which only makes it simpler to use. The Mkii includes true compressor bypass, larger metering, increased output, and an auto-switching power supply. The Mkii is a vintage channel strip with a signature sound and it is priced within reach of a project studio.
Thermionic Culture Ltd Nightingale 2-Channel ($3,999): a mic preamp, equalizer, and a compressor for two channels. The Nightingale has tube-based circuitry for Preamp, EQ, and compression. The device features high pass filters, phase reverse switches on each preamp, 48v phantom power, and a sidechain. The EQ section allows for a variable boost of bass, presence, or top. The two separate preamp/EQ’s and the mono compressor can be used individually or may be combined in three different modes by using the summing section. This unique feature allows engineers to achieve some classic high quality tube sounds as well as some more unusual and creative effects. The outputs of the preamps can be taken separately to the mixing desk before they hit the compressor. At the same time, the preamps can be internally summed through compressor to simultaneously track another sonic option.
We have just scratched the surface of outboard gear. There are countless more brands and boutique shops that make preamps, EQ’s, and compressors. Beyond that, there are many types of outboard gear besides the three we discussed. It is always a learning process; don’t get lost in the technicalities. The most important thing is to let your ears lead you as you explore outboard gear. Change settings, listen, and make notes of what you like. At the end of the line, the listener has no idea what outboard gear was in your signal chain. They don’t care whether you used the 6176 or the Nightingale. All that matters to the listener is: does it sound good?
