Useful Arts Audio SFP-60 Microphone Preamplifier

Useful Arts Audio SFP 60 Overview

Let your mic signals pop in the mix with less post-processing using the SFP-60 Microphone Preamplifier from Useful Arts Audio. Featuring a streamlined signal path, this two-channel, full-featured all-tube mic preamp offers a sound that is more clear, present, and edgy rather than dark and creamy. It's specifically designed to make vocals sound forward and intimate. The SFP-60 accomplishes this by using tubes to accentuate harmonics that make sound more clear and pleasing to the ear. An EF-806 pentode input tube adds third-order harmonic content for clarity and bite, while the final two gain stages are high-current ECC82 triodes, which contribute more second-order harmonic components for added richness or "thickness" without darkening the sound.

Unlike most preamps, which are designed to maintain a predetermined ratio of distortion to gain, the SFP-60 puts the artistic choice of distortion in your hands. At a setting of 0, the preamp is very clean it sounds "polite." A setting of 10 adds about 10 dB of gain and increases the distortion artifacts by nearly ten times. The result is an aggressive, full sound that stands out in a mix and grabs the listener's attention. This creative range gives the SFP-60 the ability to suit a variety of tracks and sources. The preamp's impulse response is tailored to avoid distortion in the time domain so as to preserve the full dynamic detail of your signal.

THE SFP-60 reproduces transients with a minimal settling time, greatly increasing the perceived clarity of the sound.

The output tube is loaded with a massive inductor rather than with a resistor the same technique used in the design of classics like the Telefunken V76.

The SFP-60 features separate internal-regulated DC power supplies for tube filaments, phantom power, and high voltage.

The high-voltage, soft-start power supply puts out over 270V of clean, regulated power to ensure maximum headroom and the lowest noise possible.

Each gain stage is single-ended, inherently class A.

The audio magnetics (input and output transformers, plate inductor) are custom-wound by CineMag.

The output transformer is built with 50% nickel core.

The frequency response is flat within 2 dB from 20 Hz to 20 kHz.

Each channel of the SFP-60 features five switches:

• Input selector (rear XLR / front instrument input)
• High-pass filter
• Input pad
• Phase reverse
• Phantom power

The front panel switches control sealed, gold-plated relays to ensure years of operation without pops and clicks.

The only active devices in the signal path are the three tube gain stages, consisting of one EF806 and one ECC82 per channel. JJ tubes are used for long life and easy replacement.

The input and output levels of the triode stages are separately controllable by detented attenuators. Using the color control, the SFP-60 provides just over 55 dB of usable gain.

The rear panel provides gold-plated XLR connectors for the transformer-balanced inputs and outputs, a ground post, and a voltage selector for 115/230V operation

Each channel features an output-level VU meter, which is op-amp buffered to ensure that the signal is not loaded by the meter.

The audio power supply features a toroidal dual-primary transformer and linear regulation for lowest noise.

Construction is fully modular, with gold-plated connectors used throughout the audio path.

The faceplate is milled from 0.190"-thick aircraft-grade aluminum for maximum rigidity, and anodized in a very dark green finish.

All markings on the front panel are laser-engraved.