Universal Audio 4-710d
Four Twin-Finity preamps, eight channels of conversion, and enough soft-limiting to keep a hot session out of the red - all for under two grand on the street.
Overview
The 4-710d is the rack answer to a complaint that followed Universal Audio's single-channel 710 Twin-Finity from the summer of 2009: it didn't come in stereo. This one is a four-channel preamp/DI built around the same continuously variable tube-to-solid-state blend as the 710. It adds a compressor on every channel, switchable inserts, an eight-channel A/D converter, word clock I/O, soft limiting, and sample rates up to 192 kHz at 24 bits.
The Twin-Finity concept is the heart of it. Each channel lets you sweep the signal path from 100-percent solid-state to 100-percent tube. It isn't a fixed-voiced box. It's a continuum you dial by ear. Around the analog meter sit six switches: phantom on/off, a -15 dB pad, mic/line selection, meter switching between output level, gain reduction, and drive, a 75 Hz low-cut, and polarity. Two more switches below the meter engage the insert and the compressor, the latter with slow or fast attack/release settings.
The compressor is where the 4-710d departs most from its single-channel ancestor. Universal Audio fitted each channel with a newly designed 1176-style compression/soft-limiting circuit. The 1176 is one of the compressors the company built its name on. The soft limiter is the safety net for the converter. The manual is plain about its limits: it helps prevent digital overs during conversion, but it is not a brick-wall limiter, and you can still clip the A/D input. In practice the reviewer found that no matter where levels went, nothing showed red in the DAW, even when the input was deliberately overloaded.
The digital side is the reason many buyers looked at this box in the first place. Eight channels of 24-bit/192 kHz conversion sit behind the four preamps, with the extra four channels available as line inputs on TRS jacks around back. Outputs are dual ADAT optical and AES/EBU on a DB-25 connector. The ADAT ports mirror at 44.1 and 48 kHz, run 4+4 at 88.2 and 96 kHz, and 2+2 at 176.4 and 192 kHz. There's word clock in and out, and the unit carries an ultra-low-jitter clock subsystem. The rear panel also holds XLR mic in, line in, line out, and balanced insert send/returns on TRS per channel. In the review session, the extra line inputs were a handy way to fold a fifth preamp, a 710 Twin-Finity, into the digital back end. A short 75-ohm BNC cable locked the 4-710d to the interface's clock, and the front-panel lock light confirmed sync.
On the bench, the numbers backed up the design. Retested through the digital output at 96 kHz, those channels showed 0.002% and 0.004% in solid-state and 1.408% and 1.621% in tube mode. Distortion climbs a lot with the tube engaged, which is the point and not a flaw. Frequency response was described as razor flat from 20 Hz to 80 kHz on the analog path, and equally flat analog-in to digital-out at 96 kHz.
In use, the 4-710d earned its keep on detail work. The same reviewer recorded vocals, acoustic guitar, congas, grand piano, and a miked Fender amp through it. He found the high-end detail and midrange body a clear step up from the preamps and converters on an Avid C|24 and 192 I/O rig. A Royer SF-24 ribbon on a Yamaha C3 grand with the blend set at 12 o'clock gave a sweet top end and solid midrange. A bass DI with the tube all the way on delivered a nice bottom, if not quite the fatness of the SSL 4000 preamps in that room. Drums were where it fell short. Kick and snare lacked the punch of higher-end preamps, and the reviewer swapped back to the SSLs for that job. Toms fared better, with plenty of stick detail.
It is not the go-to preamp for every situation, and the reviewer said so plainly. For vocals, percussion, acoustic instruments, horns, and piano, it stood head and shoulders above anything in its price range.
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