This article was originally published on September 13, 2018.
Rega's Reference Moving Coil Stage, the Aura
This reference Aura MC stage is the culmination of decades of electronic design development. They created the ultimate, fully adjustable, three stage, all symmetrical pre-amplifier designed purely to extract the very best performance from your moving coil cartridge and vinyl collection.
Built into a completely re-designed custom case, the Aura is dedicated to moving coil cartridges and stays clear of any compromises. Rega have avoided including any superfluous functions as they obstruct the signal path and degrade the sound quality. The Aura phono pre-amp incorporates remarkable and innovative design ideas. If you are a vinyl connoisseur, then the Aura MC is an absolute must hear.
Introduction And Design Innovation
The Rega Aura is a three stage, all symmetrical pre-amplifier. The first stage is a symmetrical, complementary class A amplifier, using parallel connected Linear Systems ultra-low noise FET (Field Effect Transistor) transistors configured as a symmetrical compound pair input stage. The use of FET transistors ensures there is no bias current flowing in the cartridge coil so as not to upset the delicate magnetic geometry of the cartridge. The input circuit configuration also alleviates the use of any coupling components between the cartridge output and the input stage FET transistors, which would degrade the sound. The complementary ultra-low noise FET transistors are carefully graded and matched for optimum performance. This stage drives the passive high frequency part of the RIAA equalisation stage.
The second stage is a symmetrical, class A, differential amplifier with a common base driver stage; this is also used as the active amplifier in the low frequency part of the RIAA equalisation stage. The third stage inverts the signal to provide the balanced output along with the output of the second stage; the third stage uses the same circuit topology as used in the second stage. The power supply is a symmetrical, discrete tracking power supply using fast diodes and a low noise voltage reference. Each stage has its own localised power supply and LED referenced current generators. To maximise headroom, the Aura has a power supply voltage, which is 60% higher than normally found in such a pre-amplifier. Very high quality, polypropylene capacitors have been used in the signal path. 1% tolerance polypropylene capacitors are used in the RIAA EQ stages and audio grade capacitors are used in the rest of the circuit. Gain, Mute and Mono switching is implemented using high quality relays.
REGA AURA REFERENCE MOVING COIL PRE-AMPLIFIER
Generator Source Resistance 20 Ω (Audio Precision Z Out)
Load set to 100 Ω and capacitance set to 1000 pF (Apheta and Aphelion)
Output Load Resistance 100 kΩ (Audio Precision Z In)
Input Sensitivity for 200 mV on Unbalanced Output
67 μV - 69.5 dB Gain Setting I
131 μV - 63.5 dB Gain Setting II
Gain Input to Unbalanced Output
63.5 dB Minimum
69.5 dB Maximum
50, 100, 150, 300 & 400 Ω
1000, 2000, 3200, 4300, 5700 pF
Input Overload @ 1 kHz
9.6 mV - 63.5 dB Gain Setting
4.9 mV - 69.5 dB Gain Setting
Rated Output Level
Unbalanced 200 mV
Balanced 400 mV
Maximum Output Level
Unbalanced 14.5 V RMS
Balanced 29 V RMS
Balanced Output Connections
Balanced XLR connectors pin2 positive and pin3 negative.
The positive pin2 connection on the balanced output is the same connection as the unbalanced output.
Unbalanced 100 Ω
Balanced 200 Ω
Absolute Minimum Output Load Resistance (for a –3 dB roll off @ 20 Hz)
500 Ω Unbalanced
1000 Ω Unbalanced
RIAA Accuracy (Better Than)
0.2 dB 100 Hz to 50 kHz
13.5 Hz (–3 dB) to 100 kHz (–0.2 dB)
Typically 0.03 % @ 1 V 20 Hz 20 kHz (Bandwidth 100 Hz to 22 kHz)
Output Noise Level (Unbalanced Output, A-Weighted and 15 Ω Input Load)
-77 dB V (69.5 dB Gain Setting I)
-82 dB V (63.5 dB Gain Setting II)
Read what The Ear has to say about the Rega Aura.