Golden Age Project PRE-73 DLX User Manual

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Vintage Style Pre Amplifier
PRE-73 DLX
INTRODUCTION
Congratulations on choosing the Golden Age Project PRE-73 DLX microphone preamplifier!
The PRE-73 DLX is a one-channel vintage style microphone-, line- and instrument preamplifier. The signal path uses only discrete
components like resistors, capacitors and transistors. The line and microphone input and the line output are transformer balanced, using
three different transformers, each one optimized for its purpose.
This is the way audio components were built before integrated circuits became available. The subjective sound quality delivered by
vintage equipment is often prefered over the one delivered by modern units, a situation that is even more obvious now when music is
recorded with cleansounding digital audio equipment.
The circuit used in the PRE-73 DLX 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 integrated circuits in the signal path.
- Maximum gain on the mic input is 80 dB, enough to handle passive ribbon mics with quiet sound sources.
- Gain range on the Line input: -20 to + 10 dB.
- Switchable impedance on the mic input, 1200 or 300 ohms, will change the tone of many mics.
- 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 jacks and separate output XLR and TRS jacks for flexible connections.
- Insert jack for inserting EQ´s and other units.
- External high power power supply to avoid interaction with the audio circuits and transformers.
- A solid build quality that will last many years of normal use.
The PRE-73 DLX has a number of improvement and new features compared to the PRE-73 MKII:
- Tantalum capacitors in the signal path.
- Selectable 1073-style high pass filter, 50, 80 , 160 and 300 Hz.
- Output Attenuator -7, -14, -21 and -28 dB (located after the output transformer) allows overdriving the output stage and the output
transformer for added character by lowering the output signal to a suitable level.
- The circuit board is prepared for Carnhill Mic and Line transformer and high pass inductor.
- The Insert jack can be switched in/out from the front panel. An internal jumper can select that the Insert jack always has an output
signal.
- Switchable 600 ohm Output Termination and Ground Lift on the back panel.
- Selectable Active or Passive DI input and selectable input impedance in active mode, Hi Z or 100 kohm, by internal jumpers.
- The DI signal can be selected to pass or bypass the mic input transformer by internal jumpers.
- Relays are used to control internal switching for DI input, Phantom power, Mic Low Z, Insert and Phase for shorter circuit board signal
paths. The relays are controlled by front panel switches.
- Revised gain switch for added headroom.
- Circuit board star grounding scheme.
- Revised power supply with separate regulators for the audio circuits and relay and LED circuits.

Golden Age Project PRE-73 DLX Specifications

General

Type	Microphone Preamp
Channels	1
Polarity Switch	Yes
EQ	No
Maximum Output Level	+26 dBu
Phantom Power	48V
Low Cut Filter	80 Hz
THD	< 0.1% at 1 kHz
Power Supply	24V
Input Impedance	1200 Ohms

Summary

Introduction to PRE-73 DLX

Product Overview and Core Technology

Details the PRE-73 DLX as a one-channel vintage style preamplifier using discrete components and transformer balancing.

Sound Character and Vintage Circuit

Describes the circuit's similarity to the classical 1073 module, offering a warm, punchy sound at a low cost.

Key Features of the PRE-73 DLX

Vintage Design Philosophy

Highlights the use of vintage-style discrete electronics without integrated circuits in the signal path.

High Input Gain and Impedance Options

Features up to 80 dB mic gain, switchable mic impedance (1200/300 ohm), and a high-impedance instrument input.

Line Input and Output Controls

Specifies line input gain range (-20 to +10 dB) and details output level control for gain adjustment and character.

Connectivity and Signal Routing

Includes combo XLR/TRS inputs, separate outputs, an insert jack, and Phantom Power/Phase control.

Metering and Power Supply

Features a 4-step LED output level meter and an external high-power supply for audio circuit isolation.

PRE-73 DLX Improvements Over MKII

Signal Path Enhancements

Incorporates Tantalum capacitors in the signal path and revised gain switching for headroom.

Advanced Filtering and Output Attenuation

Features a selectable 1073-style high pass filter and a multi-step output attenuator for added character.

Customization and Connectivity Features

Includes options for DI input impedance, output termination, ground lift, and relay-controlled switching.

Using the PRE-73 DLX

Basic Setup and Signal Flow

Guides on connecting power, audio sources, and outputs, and selecting MIC/LINE inputs.

Achieving Desired Tone and Character

Explains how to use the output level control and PAD to drive stages for more character.

Specialized Features and Controls

Details the use of the DI input, LOW-Z switch, high-pass filter, phase switch, and unbalanced insert jack.

Output Transformer Loading and Grounding

Discusses the 600 ohm output termination switch and the ground lift switch for noise reduction.

Customizing the PRE-73 DLX

DI Input Impedance and Mode Selection

Guides on changing the active DI input impedance to 100k ohm or converting it to passive mode.

DI Signal Path Routing

Explains how to route the DI signal directly to the gain stage, bypassing the mic input transformer.

Insert Jack and Optional Upgrades

Details disabling the output to the INSERT jack and mentions optional Carnhill transformer upgrades.

Warranty and Registration

Troubleshooting and Fuse Replacement

Advises on checking the fuse and trying a different adapter if the unit fails.

Repair and Distributor Information

Instructs users to contact resellers or distributors for repairs and warranty support.

Product Registration

Encourages users to register their unit online at the official website.