Heritage Audio decided to make exactly zero compromises on this 1073 in a 500 series package. This meant making a 3u wide module capable of holding all three vintage accurate transformers, dual concentric switches, quality push buttons and same exact PCB cards.
No downsized knobs. No transformers left out. No ICs in place of discrete class A circuitry. Just what the faceplate says: a 1073 in a 500 series format.
- 70dB 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.
- 10dB Class A Line Amplifier, Bridging input impedance, balanced and floating.
- Class A, single ended, 2N3055 driven high headroom output stage.
- High Frequency: +/-16dB shelving at 12 kHz, Baxandall type.
- Low Frequency: +/-16dB with selectable frequency shelving of 35Hz, 60Hz, 110Hz & 220Hz, Baxandall type.
- Mid Frequency: +/-18dB peaking, fixed 'Q' , selectable center frequencies of 0.36kHz, 0.7kHz, 1.6kHz, 3.2kHz, 4.8kHz , and 7.2kHz , dual inductor based.
- High Pass Filter: 18dB per octave slope, switchable between 50Hz, 80Hz , 160 Hz & 300Hz, inductor based.
- EQ Button: Switches the equalizer on or off.
- Phase Button: Flips phase 180º.
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 transformer balanced and floating.
Line input impedance: 10KOhms bridging, transformer balanced and floating.
Output impedance: Less than 75 Ohms, transformer balanced and floating, to drive a load of 600 Ohms.
Maximum output: Greater than +26dBm into 600 Ohms, greater than +32dBu into 10KOhms.
THD: Less than 0.025% at 1Khz, Less than 0.05% at 100Hz.
Frequency response: 20Hz (+0.3dB) to 20Khz (-0.2dB).