Golden Age Project | PRE-73 DLX MKII Microphone Preamp

A VINTAGE STYLE MIC PREAMP
THE DE LUXE VERSION OF THE
PRE-73 MKIII

"It was hard to find ways to improve our classic top-of-the-line PRE-73 DLX preamp that has stayed the same since 2011.
The MKII version uses almost the same circuit design but has classic style white rectangular switches and sturdy toggle switches, a reduced number of internal circuit boards and connectors, a beefed up power supply, a revised 48V phantom power supply design that can deliver the full 10 mA current according to the standard and a two position AIR EQ."

The PRE-73 DLX II 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 preferred over the one delivered by modern units, a situation that is even more obvious now when music is recorded with clean-sounding digital audio equipment.

The circuit used in the PRE-73 DLX MKII 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.
•  Custom made mic and line input and line output transformers and highpass inductor. The circuit board is prepared for the Carnhill transformers and high pass inductor.
• Traditional 1073-style gain switch that is also used to select the mic or the line input jack.
• Two combo XLR/TRS mic and line input jacks and separate output XLR and TRS jacks for flexible connections.
• Maximum gain on the mic input is 80 dB, enough to handle passive ribbon mics with quiet sound sources.
• Switchable impedance on the mic input, 1200 or 300 ohms. Changing the load impedance will change the tone of many mics.
• Gain range on the line input: -20 to + 10 dB.
• An active instrument input for guitar and bass that passes the signal through the mic input transformer, with selectable input impedance, hi-Z or 100 kohm, by an internal jumper.
• Switchable phantom power and absolute phase.
• Gain switch plastic knob and metal knobs for the other controls.
• The phantom power can deliver up to 10 mA according to the specification standard. The 6.8 kohm phantom power resistors are matched to within 0.1% to maintain good common-mode rejection in the circuit.
• Selectable 1073-style inductor based highpass filter at 50, 80, 160 or 300 Hz with a slope of 18 dB / octave.
• Selectable two position AIR EQ with a boost of about 3 or 6 dB at around 30 kHz.
• An output pad allows the user to add character by attenuating the output signal after the output transformer by -7, -14, -21 or -28 dB for overdriving the output stage and the output transformer by adding gain and then lower the output signal to a suitable level with the pad.
• A simple but effective 4-step LED output level meter.
• Tantalum capacitors in the signal path.
• Switches on the back panel for 600 ohm output termination and ground lift.
• Relays are used to control internal switching for phantom power, mic low-Z, insert and DI for shorter circuit board signal paths. The relays are controlled by front panel switches.
• Circuit board star grounding scheme.
• Power supply with separate regulators for the audio circuit and the relay and LED circuit.
• External power supply to avoid interaction with the audio circuits and transformers.
• A solid build quality that will last many years of normal use.

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