3-stage 73-style mic preamp with all-discrete high-pass filter.
The Heritage Audio 73JRII is an update to the already classic 73JR, a true 73-style mic preamp in a single 500 Series slot with added features that cover all recording needs for engineers and musicians that don't find the need to track with EQ.cEmploying only discrete circuitry and conventional components, the 73JRII is a faithful 3 stage class A 73 preamp with Styroflex and tantalum capacitors used throughout and no corners cut. The useful all-discrete class A high-pass filter has also been updated, making it sweepable from 20 to 220 Hz. The smart switched DI (automatically switches from MIC to DI mode when inserting a MONO 1/4" 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 +24v slow turn on regulation (about 20 seconds to reach full voltage). This makes the power supply of the 500 series enclosure healthier and makes the 73JR independent of the rest of the slots.
Specifications
- Microphone input impedance: HI, 1200 Ohm minimum, LO, 300 Ohm minimum
- Line input impedance: 10K Ohms bridging, transformer balanced and floating
- DI input impedance: Greater than 2 Megohms, unbalanced
- Output impedance: Less than 75 Ohms, transformer balanced and floating, to drive a load of 600 ohms (factory terminated)
- Maximum output: Greater than +26dBu 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 -125dBu EIN
- Power consumption: 86 mA per rail @+-16VDC