Golden Age Project PRE-73 DLX MKII

Description

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 MKII 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 products, 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 separate 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.

– Insert jack for inserting EQ´s and other units. The insert jack can be switched in/out from the front panel. An internal jumper can select if the insert jack always has an output signal or not.

– 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.

– 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.

PRE-73 DLX MKII manual

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In resonse to a customer asking about the difference between the PRE-73 DLX MKII and the PRE-73 DLX PREMIER:

“This is basically a matter of taste regarding what sound one prefers, not taking the outer design into account.
Many users think that the UK-made Carnhill transformers sound better, some just think they sound different. Some users wants “the real thing” and are prepared to pay some more for the Carnhill components that also include the high pass inductor. The Chinese made transformers are actually very good though.

The Premier version also has the benefit of all soldered internal connections (except for the GAIN switch connector), polystyrene capacitors in the gain stages, 0,1% matched phantom power resistors and a Neutrik Mic input combo jack. Some users will also prefer the classic look and the metal knobs.

The new DLX design is my best so far and I am very proud of it. Both versions offers a set of features and a design quality that is, as far as I know, not found in any other product on the market, regardless of price.

Check out the PRE-73 DLX PREMIER here

To sum it up, if you have the budget for the Premier version, buy it. If your budget is lower, the PRE-73 DLX MKII is also an amazing product offered at a very low price that you will most certainly be very happy with.”
Bo Medin, December 2019

PRE-73 (Project and Premier) vs the DLX models:

– Traditional 1073-style gain switch that is also used to select the mic or the line input jack.

– Two separate Combo XLR/TRS mic and line input jacks and separate output XLR and TRS jacks for flexible connections.

– 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.

– 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.

– The insert jack can be switched in/out from the front panel. An internal jumper can select if the insert jack always has an output signal or not.

– 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.

– 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.

Additional information