Heritage Audio '73 JR II - 500 Series Mic Preamp Module

Heritage Audio '73 JR II - 500 Series Mic Preamp Module

The Heritage Audio '73 Jr II is a 500 series, 1073 style mic pre-amp that employs fully discrete, class A circuitry. The Jr has added features that will cover the needs for engineers and musicians who want to record without EQ. 

Employing only discrete circuitry and conventional components, the 73 JR II is a faithful 3 stage all Class A 73 preamp. Styroflex and tantalum capacitors have been used throughout. No corners were cut.

The useful all discrete Class A hi pass filter has been updated, making it sweepable from 20 to 220 Hz. Now it is even easier to make your low end tighter without affecting desired frequencies.

The Line mode allows for reamping of prerecorded tracks and it´s perfect for adding some Class A color to lifeless recordings.

The smart switched DI (automatically switches from MIC to DI mode when inserting a MONO ¼” jack) is an all discrete Class A JFET circuit ahead of the MIC transformer, so all the juice is there. Since its introduction in 2013, it has become a classic DI for bass.

Finally, special care has been taken with power handling, implementing internal +24 V slow turn on regulation (about 20 seconds to reach full voltage).This makes your 500 series enclosure´s power supply healthier and makes the 73JR independent of the rest of the slots.

Specifications

• Microphone input impedance: HI=1200 Ω  minimum, LO=300 Ω minimum. Higher gain positions gradually have greater impedances, perfect for lo gain ribbon mics. Input is transformer balanced and floating.
• Line input impedance: 10 kΩ bridging, transformer balanced and floating.
• DI input impedance: Greater than 2 MΩ, unbalanced.
• Output impedance: Less than 75 Ω, transformer balanced and floating, to drive a load of 600 Ω (factory terminated).
• Maximum output: Greater than +26 dBu into 600 Ω.
• THD: Less than 0.025 % at 1 kHz, less than 0.05 % at 100 Hz.
• Frequency response: 20 Hz (+0.3 dB) to 20 kHz (-0.2 dB).
• Maximum gain: Slightly greater than 80 dB.
• Noise: Less than -125 dBu EIN.
• Power consumption: 86 mA per rail ±16 V DC.