GOLDEN AGE PRE73 MK3 Microphone preamp

The PRE-73 MKIII is a one-channel vintage style microphone-, line- and instrument preamplifier. The signal path uses only discrete components like resistors, capacitors and transistors. The in- and output is transformer balanced, using two different transformers, each one optimized for its purpose. This is the way audio components were built before integrated circuits became available.

The circuit used in the PRE-73 MKIII is similar to the preamp section in the classical 1073 module with a corresponding sound character that is warm, punchy, sweet and musical. These classic characteristics have been heard on countless recordings through the years and it is a versatile sound that works very well on most sound sources and in most genres.
The essence of this sound is now available at a surprisingly low cost, making it available to nearly everyone.

Features  :

• Vintage Style electronics. No intergrated circuits in the signal path.

• Maximum gain in MIC mode is 80 dB, enough to handle passive ribbon mics with quiet sound sources.

• GAIN switch range 20 - 80 dB. GAIN/LINE mode switch, gain is reduced by 30 dB in LINE mode.

• Selectable two position high frequency AIR boost eq, 3 or 6 dB @ 30 kHz.

• Selectable 6 dB/octave two frequency high pass filter at around 40 (HP1) and 170 Hz (HP2).

• Tantalum capacitors in the signal path.

• Switchable impedance in MIC mode, 1200 or 300 Ohms, will change the tone of most mics. The input impedance in LINE mode is 10 kohm.

• Switchable phantom power and absolute phase.

• A high-impedance instrument input for any sound module, electric guitar or bass.

• A simple but effective 4-step LED output level meter.

• The output level control makes it possible to make fine gain adjustments and also to overload the main gain stage(s) for more character and then lower the signal to a suitable level before the output stage.

• Combo XLR/TRS input jack and separate output XLR and TRS jacks for flexible connections.

• Insert jack for inserting EQ´s and other units.

• Selectable 600 ohm output termination.

• The pcb is prepared for the Carnhill input transformer.

• External power supply to avoid interaction with the audio circuits and transformers.

• A solid build quality that will last many years of normal use.

The MKIII has the following new features compared to the MKII:

• Tantalum capacitors in the signal path.

• Selectable two position high frequency AIR boost eq, 3 or 6 dB @ 30 kHz.

• Selectable two frequency high pass filter, 6 dB/octave at 40 or 170Hz.

• The pcb is prepared for the Carnhill input transformer.

• Revised and less complicated GAIN switch with a separate switch for MIC/LINE selection.

• All GAIN settings can also be used in LINE mode .

Designed for high-definition field production environments, the studio-quality MP-1 is an ideal line-driver for critical radio, television, and film applications.

The MP-1 is extremely durable and easy to use. With rugged mechanical and electrical construction and high-quality components it will provide years of superb audio performance under the most punishing field conditions.

• Superb audio specifications
• 66 dB of gain, in eleven discrete steps
• Transformer-balanced input and output
• Phantom power - 48 volt or 12 volt
• High pass filter @  80 Hz or 160 Hz, 6 dB/octave
• Limiter makes unit virtually "unclippable“
• High current line output drive
• Excellent immunity to RF interference.
• Battery power (two x AA)
• Durable mechanical construction

The AD2022 is Avalon's fourth generation of fully discrete, symmetrical Pure
Class A microphone preamplifiers. The dual mono AD2022 includes the original
sonic capabilities and transparency of the M2, M22 and M5 preamplifiers plus
several additional features, including selectable microphone source loading for
optimized cable/mic matching, improved high-voltage Class A regulated power
supplies, two high Z instrument inputs, variable-passive high pass filter, teflon/
silver wiring and doubled plated circuit boards for superior low level signal transfer.
 
AD2022 FEATURES
Symmetrical Pure Class A design, two channels
Microphone and hi-Z instrument inputs
Gain switched 4dB steps plus +/- 3dB fine output trim 
Selectable microphone input impedance matching 
Low noise -126dB EIN
Ultra high quality, low-ratio, balanced input transformer
Balanced, high-current Class A output to +36dB
Large illuminated analog VU meters and twin peak LED's
Regulated phantom power supply +48v 
Input polarity phase reverse 
High headroom +36dB input before overload
Input -20dB pad for high level signals
Sealed silver relays for all signal routing
External AC 150w toroidal power chassis
Fully discrete Class A regulated audio power supplies
Deep, musical sound-stage, transparent amplification

MICROPHONE INPUT
The AD2022 incorporates the most advanced high-performance microphone
transformer available. Split low-ratio primary windings are carefully combined
within a custom mu-metal core for extended smooth frequency response and
very low distortion.  Sealer silver relays are used for minimal signal invasion. 
The input signal selector, high pass filter, polarity-phase reverse, +48v power
and the 20dB input attenuator all utilize local sealed relay operation. A variable
passive high pass filter provides a minimum phase shift design while eliminating
low frequency rumble, wind noise and mechanical vibration at sub sonic frequencies.

SYMMETRICAL PURE CLASS A DESIGN
Two 100% discrete, high-voltage, symmetrical Pure Class A signal amplifiers
are utilized per channel. The first operates in a cascaded-cascode FET
configuration while the second stage amplifier is fully bipolar. The twin amplifiers
share the total available gain requirement. This shared architecture increases
the high level headroom capability, improves transient response and doubles the
internal bandwidth of the ultra-high performance pure Class A signal amplifiers.
OUTPUT and METERING
High-current DC coupled, Class A discrete amplifiers are utilized for the output
drive interface with +36dB capability into all known loads.  Two large, high-quality
analog VU meters indicate accurate signal readings while bi-color LED's offers
peak indication at 0dB and +20dB.

AD2022 PREAMPLIFIER SPECIFICATIONS
 
Circuit Topology:  Twin cascode FET and bipolar low level signal amplifiers,
high-voltage, 100% discrete, symmetrical Pure Class A 
Input Type and Load:  Transformer balanced low-ratio, 50, 150, 600 and 1k5
ohm input load selection  
Maximum Mic Level:  +36dB balanced XLR pin 2 hot (with -20dB passive
attenuator) 
Maximum Instrument Level  +18dB at 100k ohms instrument input level,
standard mono 1/4 inch jack 
Input Attenuator:  -20dB resistive pre transformer primary, sealed silver relay 
Phantom Power:  +48v regulated 50mA capability, sealed silver relay 
High Pass Filter:  Passive, variable from 30Hz to 185Hz @ 6dB per octave,
sealed silver relay. 
Polarity Reverse:  Sealed silver relay on microphone input 
Gain Range Input:  +20dB to +64dB in 4dB steps 
Gain  Output Range:  +/- 3dB variable conductive plastic potentiometer 
Maximum Output Level:  +36dB balanced 600 ohms, DC coupled, discrete
symmetrical Pure Class A 
Output Type:  XLR connector, pin 2 hot 
Noise EIN Unweighted:  -126dB 150 ohm 
Noise 20kHz Unweighted:  -102dB 
Distortion THD, IMD:  0.05% nominal 
Frequency Response -3dB:  1Hz to 120kHz transformer limit 
System Bandwidth:  DC to 1MHz 
Output Meter:  High quality, illuminated analog VU meter 0dB = +4dB. 
Peak Meter:  Bi-color LED's 0dB and +20dB peak detection circuit. 
AC power supply B2T:  External toroidal 100V to 240V, 50-60Hz selectable,
150 watts maximum. 
Cables:  90V ac, 4 pin male power input connector, B2T required, internal
DC regulation  
Dimensions:  19 x 12 x 3.5 in (482 x 305 x 89mm) 
Weight:  15lbs (6.8kg) 
Dimensions - Shipping Carton:  24 x 21.5 x 7.5 in (610 x 546 x 190mm)  
Weight - Packed:  25lbs (11.4kg) 

The PRE-73 Mk2 is the first one-channel low-cost preamp on the market that is using a fully discrete signal path with three separate transformers for the balanced mic input, the line input and the output.

The circuit is very similar to the classical preamp section of the Neve 1073 pre/eq module with a corresponding sound character that is warm, punchy, sweet and musical.
This classical sound has been heard on countless recordings through the years and it is a versatile sound that works very well on most sound sources and in most genres.

The PRE-73 Mk2 has a maximum gain of 80 dB on the mic input and the gain range on the Line input is -20 to + 10 dB. There is also a high-impedance instrument input.

The PRE-73 Mk2 is perfect for almost any signal source, no matter if it's a microphone with a high or low sensitivity (like a passive ribbon mic), a syntheziser or sound module or an electric guitar or bass.

The input impedance of the microphone input can be switched between 300 and 1200 ohms, which makes it possible to affect the tone of most microphones. There is also phase switch and an simple 4-step LED signal level meter.

The output level control makes it possible to make fine gain adjustments and also to overload the main gain stage for more character and then lower the signal to a suitable level before the output stage.

The Mk2 update consists of:
- An unbalanced insert jack (nominal level about 18 dBu) added on the back panel for inserting units like the coming GAP EQ-73, a three band eq.
-  LED meter levels adjusted.
- 600 Ohm termination resistor and jumper added to power supply board (accessible from the inside of the unit).
- Revised Gain switch, turning the know clockwise now increase the gain.
- Reduced noise at high gains by a change to the power supply grounding scheme.

Two channel classic Focusrite ISA transformer-based preamps Front panel, per channel:

• 1/4" instrument input
• Variable input impedance - Low, ISA 110, Medium, High
• Input selection - Mic, Line, Instrument
• 0 - 30 dB/30 - 60 dB gain switch
• Phantom power switch
• Phase invert switch
• 0 - 60 dB gain in 10 dB steps
• 0 - +20 dB continuously variable trim
• Variable high-pass filter with on/off switch
• Insert point on/off switch
• Eight-LED user-calibrated level meters
• Single power switch

• XLR-F mic inputs
• 1/4" TRS line inputs
• 1/4" TRS Sends
• 1/4" TRS Returns
• XLR-M line output
• Single peak meter calibration dial
• Single IEC power socket