Audioroot uPRE MKII Battery-Powered Stereo Microphone Preamp

The Audioroot uPRE MKII is a compact, battery-powered two-channel microphone preamp with a 24-bit/192 kHz AES or S/PDIF digital output. It adds two more mic inputs to a field mixer, digital recorder, or camera. The MKII succeeds the original uPRE introduced in 2010, with a redesigned circuit and the new digital output. Each electronically balanced mini XLR input has its own 48V phantom power, an 80 Hz low-cut filter, and a gain trim from −50 dB to +80 dB.

A stereo link sets both channels from one knob, and a pair of recessed switches adds an M/S decoder on the analog output, which also works as a mono mix of both mics. Analog and digital outputs share one mini XLR5 connector (unbalanced left and right plus AES), and a rotary selector sets the converter’s sample rate from 44.1 to 192 kHz or turns it off to save power.

The uPRE MKII runs on two 9V batteries (alkaline or 9V lithium-polymer rechargeables) or an external 9 to 18V DC supply through a 4-pin Hirose input, and it switches to external power automatically. Battery life reaches about 10 hours with dynamic mics and the converter off, and about 5 hours with two condenser mics and the converter on. The hybrid polyamide and aluminum housing measures 130 × 85 × 30 mm and weighs 255 g.

Features

Two electronically balanced mini XLR (TA3) mic inputs
48V phantom power on each channel
Gain range from −50 dB to +80 dB
80 Hz low-cut filter (12 dB/octave) on both channels
Stereo link and switchable M/S decoding, with a mono mix mode
AES or S/PDIF digital output at 24-bit, 44.1 to 192 kHz
Unbalanced analog stereo output on mini XLR5
Three-LED level meter per channel and a low-battery indicator
Two 9V batteries or 9 to 18V DC through 4-pin Hirose, switched automatically
Rugged hybrid polyamide and aluminum housing, 255 g

Specifications

Inputs and Outputs
Mic Inputs	2 × electronically balanced, Switchcraft mini XLR (TA3)
Input Impedance	> 5 kΩ
Phantom Power	48 V on each channel
Low-Cut Filter	80 Hz, 12 dB/octave, both channels
Analog Output	Unbalanced stereo, Switchcraft mini XLR5 (TA5)
Digital Output	AES (default) or S/PDIF, 24-bit
Sample Rates	44.1, 48, 88.2, 96, 176.4, and 192 kHz
Maximum Output Level	+17 dBu (600 Ω load)
Audio Performance
Gain Range	−50 to +80 dB
Maximum Gain	> 80 dB (50 Ω source, 600 Ω load)
Distortion	0.003% below 40 dB gain 0.005% at 60 dB gain
Equivalent Input Noise	−128.8 dBu at maximum gain (200 Ω source)
Bandwidth (±3 dB)	10 Hz – 70 kHz
Controls	Stereo link M/S decoding (mono mix mode)
Metering	3 LEDs per channel Power and low-battery LED
Power
Batteries	2 × 9V (6LR61 or PP3)
External Power	9 – 18 V DC, 4-pin Hirose (HR10A-7P-4P mating connector), switched automatically
Low-Battery Threshold	13 V
Battery Life	5 hours typical with 2 Schoeps CMC6Ug and ADC on 10 hours with dynamic microphones and ADC off
Power Consumption at 12 V	92 mA (48 V off, ADC off) 130 mA (48 V on, ADC off) 155 mA (48 V on, ADC on)
Power Consumption at 18 V	62 mA (48 V off, ADC off) 85 mA (48 V on, ADC off) 100 mA (48 V on, ADC on)
General
Housing	Hybrid polyamide/aluminum, anodized and engraved face plates
Dimensions	13 × 8.5 × 3 cm 5.12 × 3.35 × 1.18 in
Weight	255 g (8.99 oz)