REGA Aura - Amplifier Manual

Introduction and Design Innovation

The function of a phono pre-amplifier is to match the output from a pick up cartridge to the input of a line level amplifier. It is required to amplify the very low signals produced by the cartridge and also to equalise the sound in accordance with the RIAA record cutting standard. Rega believes that moving coil and moving magnet cartridges require different types of phono preamplifiers to achieve optimum performance. The Aura is therefore dedicated to moving coil cartridges and stays clear of any compromises. We 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. For those interested in the technical details, these innovations are described more fully in the next section of this manual. Alternatively, you can simply switch on, sit back and let the Aura speak for itself.
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.

Earth Grounding

The Aura uses a Class I earth system, where the case metalwork is connected to the line safety earth, by means of the mains lead. The internal signal earth is linked to this earth by the use of a network to eliminate the risk of earth/ground loops. This earth method provides a safe and efficient discharge path for any static charge generated by the cartridge.

Installation

The Aura will work well on most surfaces, such as a shelf or a table, provided there is sufficient air around it to prevent overheating. To avoid any possible magnetic interference and increased hum levels, position the Aura as far away from the turntable as the tonearm lead will allow. If possible, try to place the Aura to the left of the turntable. Ideally equipment should be placed next to one another in a line. This keeps the most delicate electronics away from other transformers. Try not to stack other hi-fi components, on top of, or directly beneath the Aura. If this is unavoidable, use an equipment stand. The heat produced by the amplifier, although minimal, is dispersed to the air by the case, particularly the underside. Ensure that the case has an uninterrupted air passage around it.
The Aura weighs 13 kg, so take great care when lifting and please ensure the shelf or stand you are using can safely support this weight. Please refer to your stand manufacturer's manual for maximum load capacity.

Connections and Supplied Cables

Connections

The input can be made via RCA (phono) connectors and the output via either RCA (phono) connectors or balanced XLR connectors (pin2 positive and pin3 negative). The input and output sockets are marked by colour to indicate left and right channels, White for LEFT and Red for RIGHT. If your turntable has a separate Earth wire, firmly connect it to the terminal provided on the rear panel. N.B. Always switch both pre and power amplifiers off before changing the leads.

Mains Lead (Supplied)

A Rega designed, fully shielded, high current capacity mains power lead is included.

High Quality Interconnect (Supplied)

A Rega designed high quality RCA (phono), unbalanced interconnect is included. It was used throughout the design and development of the product and can be considered as a component rather than an accessory. The Rega cable is double shielded and exhibits an extremely low capacitance offering uniquely high levels of quality and performance.

Cartridge Selection

The Aura phono pre-amplifier is not suitable for use with any moving magnet (MM) cartridges; it can only be used with moving coil (MC) cartridges. The Aura has been designed to work with most manufacturers' moving coil cartridges.
There are five different input load and capacitance settings. Select the required load and capacitance to match to that specified by the cartridge manufacturer. Note: It is permissible to try different loading capacitance conditions as sometimes changing the resistive and capacitive loading gives a different sonic performance more suited to your personal taste. Your Rega dealer will be able to give guidance to help match your specific cartridge to the correct gain settings. It is worth noting some 'legacy' pre-amplifiers exhibit higher resistive and capacitive loading.

Powering Up

The Aura is activated by depressing the ON/OFF switch situated to the left of the front panel. Power on is indicated by the REGA LOGO in the centre illuminating red. It is recommended to activate the Aura before the power amplifiers and deactivate after they have been switched off. After switching off, the indicator will extinguish. This Rega pre-amplifier circuit has been carefully designed to work with a minimal "warm up" period. Some manufacturers and retailers may recommend leaving amplifiers permanently switched on. Rega cannot condone such practice in these environmentally sensitive times. We would recommend that your Rega amplifier is always switched off after use. Full sound quality is attained after less than ten minutes (a process speeded up by playing music).

Gain

Please note: mute or turn the volume control to minimum when changing the gain setting. The gain setting switch selects the voltage gain of the phono amplifier. Gain I selects 69.5 dB (switch out) and Gain II selects 63.5 dB (switch in); this will provide an input sensitivity of 67 µV and 131 µV respectively for an output level of 200 mV unbalanced and 400 mV balanced. The balanced output is effectively 6 dB higher than the unbalanced output. It is advisable to start with the lower gain setting II and if necessary; increase the gain level to I if more level is required for lower output cartridges. Because the balanced output is effectively 6 dB higher, it could be advisable to select gain II setting when using the balanced output; this will also depend greatly on the sensitivity of the connected amplifier.

Capacitance

There are five different input capacitance settings of 1000 pF, 2000 pF, 3200 pF, 4300 pF & 5700 pF. Select the required capacitance to match to that specified by the manufacturer in the cartridge specifications. It is permissible to try different loading conditions as sometimes changing the capacitance gives a different sonic performance more suited to your personal taste; this also applies if there is no loading capacitance specified by the manufacturer. To match some 'legacy' pre-amplifiers, select 5700 pF. The 1000 pF setting is optimised for the Rega range of MC cartridges.

Load Settings

There are five different input load settings of 50 Ω, 100 Ω, 150 Ω, 300 Ω & 400 Ω. Select the required load to match to that specified by the manufacturer in the cartridge specifications. It is permissible to try different loading conditions as sometimes changing the load gives a different sonic performance more suited to your personal taste. To match some 'legacy' pre-amplifiers, select 400 Ω. The 100 Ω setting is optimised for the Rega range of MC cartridges.

Mute

Allows you to mute the signal when changing the gain setting, in-between tracks or when changing records.

Mono

This function allows you to play mono recordings via a stereo cartridge.

Overview

Specifications

General Conditions
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

Input Load
50, 100, 150, 300 & 400 Ω

Capacitive Load
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.

Output Resistance
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

Frequency Response
13.5 Hz (–3 dB) to 100 kHz (–0.2 dB)

THD
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)

AC Supply
230 V & 115 V Nominal +/- 10 %

Power Consumption
15.3 W