User Manual

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Model 4-710d Overview
The Universal Audio 4-710d, with its four mic preamps derived from our TEC award-winning UA Model
710 Twin-Finity Mic/Line/Hi-Z Preamplifier, combines our highly revered analog tube and solid state
preamplification technology... but with a twist. Its unique phase-aligned Blend controls allow the user
to literally dial in the desired sound, from precise ultra-clean solid-state tones to fat tube presence
and overdriven crunch, or anywhere in between. Additionally, each of the four mic preamp channels
has an 1176-style analog compressor that can be individually enabled for each channel.
Other features include JFET Direct Inject inputs (which allows for the direct connection of an electric
guitar or bass, or any instrument with a magnetic or acoustic transducer pickup); monolithic balanced
output stages; +69 dB of gain; +48V power and a -15 dB pad for the mic inputs; polarity inverts and
75 Hz low cut filters; output and “Drive” (input) VU metering; a universal auto-sensing internal power
supply that allows for operation at any voltage between 100 and 240VAC; and a 2U, rack-mountable
design for studio or stage.
4-710d Vacuum Tube Preamp
The 4-710d high voltage (285 VDC) Class-A tube preamp section is based upon both classic guitar
amplifier design and classic tube mic preamp design. The circuit utilizes a 12AX7 tube for warmth and
roundness and is the second gain stage, located downstream from the Gain control pot. This allows
the circuitry to be overdriven by the first stage into anything from mild harmonic distortion to all-out
grunge; however, the transition to tube saturation is extremely gentle. The result is the gradual onset
of harmonic overdrive—no hard clipping here. As an example, the transition from 1% THD to 4% THD
occurs over a 14 dB range. Because of its multiple gain stages, with a Gain control pot between them
(as well as a Drive Meter that displays the signal level entering the second stage), a wide variety of
tonal possibilities can be dialed in, from gentle warmth to extreme grit.
4-710d Solid-State Preamp
The 4-710d solid-state preamp circuitry utilizes Universal Audio’s transimpedance design for precision
sound and ultra-low distortion, delivering the highest possible quality of signal from input to output.
The term “transimpedance” refers to transistor configurations that employ current feedback to provide
gain and distortion immunity without the loss of sonic detail or musicality. Designed for applications
requiring the ultimate in transparent amplification with little or no coloration, its razor flat and
immensely wide frequency response yields highly accurate results and minimizes artifacts on the way
to the recording medium.
Noise and distortion are kept to near-theoretical minimums so critical signals may be generously
amplified without degrading the quality or character of the sound source. Zero-coloration preamps
such as these are especially useful for capturing the sound source with its original qualities and
character so that later processing may occur with maximum flexibility. There are no transformers or
tubes in the preamp signal path, and the 1176-style compressor/limiter (located after the
preamplifier) can be switched out as desired to eliminate permanent audio coloration. For many users,
the useful characteristics of these devices are preferred at the mix stage—and are commonly
implemented using DSP processors and plug-ins with excellent (and reversible) results, such as those
found on Universal Audio’s UAD plug-in platform.
About “Class A”
Most electronic devices can be designed in such a way as to minimize a particularly unpleasant form
of distortion called crossover distortion. However, the active components in “Class A” electronic
devices such as the 4-710d draw current and work throughout the full signal cycle, thus eliminating
crossover distortion altogether.