Heritage Audio '73 Junior 500 Series Microphone Preamp

Sku #J00704000000000

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Slimmed down version of the 1073/500 module.

Following the success of the 1073/500 module, the '73 JR is a mic preamp in a single 500 series slot with some added features that will cover all the recording needs for engineers and musicians that don´t find the need to track with EQ. Employing only discrete circuitry and conventional components, the '73 junior is a faithful 3 stage all class A 1073 preamp. Styroflex and tantalum capacitors have been used throughout. No corners were cut. A useful all discrete class A hi pass filter has been added, essential for recording everything with the exception of probably kick drum and bass. 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. Finally, special care has been taken with power handling, implementing internal +24v slow turn on regulation (about 20 seconds to reach full voltage ).This makes your lunchbox PSU healthier and makes the 73JR independent of the rest of the slots.

  • 80dB Class A Microphone preamplifier
  • HI-LO selectable minimum input impedance, balanced and floating
  • High gain positions show a higher impedance, ideal for old ribbon mics
  • 50Db Class A Line preamplifier, bridging input impedance, balanced and floating
  • All discrete Class A Ultra High Impedance J-Fet Direct Input on a high quality Neutrik Jack
  • Class A single ended, 2N3055 driven, high headroom output stage
  • PAD: 20dB Mic input attenuation ahead of the input transformer to avoid overloading it
  • HI PASS FILTER: Active all discrete Class A 3rd order Bessel, 80Hz Hi Pass Filter 18dB/octave slope
  • OUTPUT control to allow overloading of the preamp
  • Internal slow turn-on +24v power supply for lower inrush current, which improves your lunchbox performance
  • Carnhill Input and Output transformers
  • 3 gain stage, genuine modular card construction. All active circuitry is on pluggable cards for easier service

If you don't need to track with EQ, then the '73 JR is the right choice for you.


'73 Junior 500 Series Microphone Preamp Specifications:

  • Microphone input impedance: HI, 1200 Ohm minimum, LO, 300 Ohm minimum. Higher gain positions gradually have greater impedances, optimum for lo gain ribbon mics. Input is Carnhill transformer balanced and floating.
    Line input impedance: 10K Ohms bridging, Carnhill transformer balanced and floating.
    DI input impedance: Greater than 2 Megohms, unbalanced.
    Output impedance: Less than 75 Ohms, Carnhill transformer balanced and floating, to drive a load of 600 ohms (factory terminated).
    Maximum output: Greater than +26dBm into 600 ohms.
    THD: Less than 0.025% at 1 Khz, less than 0.05% at 100Hz.
    Frequency response: 20Hz ( +0.3dB ) to 20Khz (-0.2dB)
    Maximum gain: Slightly greater than 80dB
    Noise: Less than -100dBm.
    Power consumption: 88 mA per rail @+-16VDC.
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