Heider FD312 H2

The operational amplifiers are the pure heart of any preamp like the Heider® H2. We naturally wanted to stay as close as possible to the discrete Studio Systems opamps from the early '70's. In a current commercially available product, we strongly believe that our potted CA-0252 opamps are the closest thing alive. Each Heider® H2 contains two of these glorious discrete blocks of love.

Each and every Heider® FD312 H2 is hand assembled, burned in and tested at CAPI headquarters in Nashville Tennessee.

Key Operating Features:
In MIC mode, the stepped PREAMP GAIN ranges from +25dB to +60dB, with an

input impedance of 450 ohms.

In LINE mode (MIC pushbutton out or disengaged), the stepped PREAMP GAIN ranges from -14dB to +21dB, with an input impedance of 9K ohms.

Sliding the PCB mount Input Z switch to '200' when in MIC mode will decrease the gain by 3dB while decreasing the input impedance to 200 ohms. Since the upper ten PREAMP GAIN steps are also in 3dB increments, this allows for many creative tonal combinations.

The PAD pushbutton equates to 16dB of attenuation in either MIC or LINE mode. With the PAD pushbutton engaged while in MIC mode, the input impedance is 800 ohms.

The stepped CHANNEL FADER switch and 2nd stage booster amp provide a range of -16dB to +12dB in addition to the above-mentioned preamp gain ranges. This equates to a maximum gain of 72dB when in MIC mode with the Input Z switch set to '450' and 69dB when in MIC mode with the Input Z switch set to '200'.

Accurate metering of the final output signal is achieved using LM339 quad comparators in a 'console' style configuration.

Physically and electronically fully VPR compliant with current draw less than 101mA per rail (under typical operating conditions)