FIG. 1: Taylor''s K4 Equalizer operates on either two C batteries or the included external power supply. A front-panel power LED changes from green to red when battery power is running low.
The Taylor K4 Equalizer was designed by pro-audio legend Rupert Neve to process the direct output of Taylor acoustic guitars fitted with the Taylor Expression System. The latter consists of three internally placed transducers and their associated active electronics, a system available only to Taylor guitars (300 Series models and higher). The K4, however, can be used with any guitar with a pickup or any other electric instrument. Some studios, in fact, are reportedly using the K4 as a combination mic preamp and equalizer to record instruments other than guitar. (The K4 does not offer phantom power for condenser mics, and Taylor emphasizes that the unit's chief function is as a preamp/EQ for acoustic instruments that have passive or active electronics.)
Pretty and Portable
The compact K4 is designed for tabletop use. The unit can also be mounted in a rack tray and is sturdy enough to sit on the floor when used as a DI. The K4's recessed front panel has three center-detented, continuously variable rotary gain controls, each providing up to 10 dB of boost or cut for the unit's three bands of EQ (see Fig. 1). The low and high bands have shelving filters. The low band's corner frequency is fixed at 450 Hz, and the high band is fixed at 1.6 kHz. The widely overlapping midrange EQ is parametric and has a frequency range that can alternately be set at 80 to 800 Hz or 800 to 8,000 Hz. Two other continuously variable rotary controls adjust the midrange EQ's center frequency and the Q (a bandwidth control), respectively. A highpass filter that is always active has an 18 dB-per-octave rolloff below 30 Hz.
Also on the front panel are a mute button and center-detented, continuously variable main- and headphone-volume rotary controls. These rotary controls are attenuators that completely silence audio when in the fully counterclockwise position. When the Mute button is pushed in, the K4's main outputs are silenced, but signal at the front-panel headphone-output jack and rear-panel tuner output are unaffected. (The tuner output sends a pre-EQ signal to your external tuner.) That allows you to tune your guitar or warm up your chops in a live setting without your practicing being amplified. The K4 is a single-channel device; the headphone output has monaural output to left and right channels, which sounds great.
Rounding out the K4's front panel are buttons for phase-inversion, power, and activation of an effects loop. Pushing in the Loop button sends the signal to access an external signal processor (such as a compressor or delay unit) connected to separate TRS send and receive jacks on the K4's rear panel (see Fig. 2). A push-button switch next to those jacks selects either pre- or post-EQ for the loop's send jack.
On the K4's rear panel are a combo (TRS and XLR) input jack and separate TRS line-level and XLR mic-level outputs — all transformer-balanced but compatible with unbalanced lines. Taylor recommends using the K4's TRS input jack to connect instruments with active electronics and the XLR input (which has a higher sensitivity than the TRS input) for instruments with passive electronics or for dynamic microphones. It ships with a 15-foot-long balanced cable fitted with TRS plugs on each end for use with Expression System — equipped Taylor guitars.
FIG. 2: The K4''s transformer-balanced input section can accommodate instruments that have either active or passive electronics, as well as dynamic microphones. The tuner output is always on, even when the main outputs are muted.
A ground-lift switch, DC-power connector (for use with the provided wall-wart power supply), and battery compartment complete the K4's rear panel. The K4 can operate on two C batteries without interruption for up to ten hours when the external power transformer is disconnected.
With the Expression System
For all of my tests of the K4, I routed the unit's output to my Apogee Rosetta A/D, with the latter's calibration trims maxed out to give considerable extra gain. I first directly patched a Taylor 30th Anniversary Grand Concert XXX-MS acoustic guitar fitted with the Taylor Expression System into the K4's TRS input. The Expression System produced a far more natural and realistic reproduction of the instrument than any DI I'd ever used.
For recording, however, the K4's output level was problematic. On an arpeggiated guitar arrangement played with a flat pick, the K4's fixed gain initially couldn't output enough level to attain 0 dBfs at the Rosetta — even with mild EQ boost in two bands and all attenuator controls in the signal path set for maximum output. On a subsequent project in which a guitar was strummed aggressively, the K4 registered 0 dBfs on a couple of isolated peaks.
The K4's EQ sounded beautiful, though I would have preferred EQ bypass buttons and adjustable low- and high-band corner frequencies to work with. Because I couldn't apply shelving EQ to the top octave, I often used a little midband EQ with a broad Q setting to boost or cut highs centered around 8 kHz, while nulling the high-band EQ to avoid affecting mids. I wish that the midrange band's frequency control were marked to indicate frequency settings between its extreme values.
Other Studio Applications
I got good results patching my passive Kramer Pioneer electric bass guitar into the K4's XLR input (using a custom-wired cable with the cold signal shunted to ground). The sound was big, with a slightly pillowy rather than present timbre. The fixed 450 Hz corner frequency on the K4's low-shelving EQ was too high to allow pumping up the bottom end on the bass-guitar track without also introducing midrange mud. That wasn't an issue for me, however, because I always record electric bass flat.
Plugging my '62 Strat directly into the K4's XLR input, the sound lacked sparkle. The top end sounded dull and rounded off, probably because of excessive pickup loading. The XLR input's impedance is roughly 500, which is very low for DI duties. Yet plugging a passive electric guitar or bass into the K4's TRS input, which has a 15 k input impedance, wasn't a solution for recording because that signal path doesn't supply enough gain for amplifying passive instruments. You can, of course, use external gear such as a compressor to provide extra gain as needed, as long as the track needs such processing to sound right.
I also used the K4 as a preamp for a Royer R121 ribbon mic to record my Strat through a Roland Micro Cube amp. Even with the amp cranked to the max (producing 95 dB SPL at the mic's position) and the K4's main volume also fully turned up, the K4's output signal still fell a few decibels shy of registering 0 dBfs on my similarly cranked Rosetta. Even so, the sound was incredible — warm, present, and chunky, with nicely rounded transients.
The Taylor K4's gain structure works best with -10 dBV systems. If you're running a +4 digital setup, you'll probably be frustrated with the K4's limited fixed-gain design. The restricted functionality of the K4's low- and high-band EQ also makes the unit an unrealistic choice for an all-purpose front-end box for recording applications.
But in its primary role as a complement to Taylor guitars that have been fitted with the Expression System, the unit shines. Owners of that system will love what the K4 does for their instrument's tone. And the K4's ability to serve as a DI for bass and a preamp for miked electric guitar tracks is sweet icing on the cake.
EM contributing editor Michael Cooper is the owner of Michael Cooper Recording, which is located in beautiful Sisters, Oregon.
Analog Inputs (1) balanced TRS/XLR combo, (1) balanced return Analog Outputs (1) balanced XLR, (1) balanced/unbalanced TRS line,
(1) balanced TRS send, (1) ¼" TS tuner out,
(1) ¼" headphone out Output Level (main outs, 600 load) +20 dBu, ±1 dB Low EQ (±1.5 dB) shelving, ±10 dB at 450 Hz Mid EQ (±1.5 dB) fully parametric, 80-800 or 800-8,000 Hz range,±10 dB, continuously variable Q control High EQ (±1.5 dB) shelving, ±10 dB at 1.6 kHz Frequency Response (+6 dBu output) 35 Hz-20 kHz, ±2 dB THD & Noise (1 kHz, +15 dBu output) <0.006% Equivalent Input Noise (main outs, EQ flat) < -86 dBu, XLR in, 150 load
< -125 dBu, TRS in, 40 load Dimensions 3.25" (W) × 6.75" (H) × 8.5" (D) Weight 4.3 lbs.
OVERALL RATING (1 THROUGH 5): 4
PROS: Beautiful-sounding EQ and headphone circuit. EQ bands overlap. Highly portable. Lots of bells and whistles included.
CONS: Corner frequencies for low and high EQ bands cannot be adjusted. Weak fixed gain complicates use with +4 dB nominal digital systems.