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After nearly 10 years of existence, the modern classic Heider® FD312 has gotten a rework! We are pleased to present the
Heider® FD312 H2.
Besides the immediately apparent monochrome front panel and controls, here are the main differences:
A custom exclusive CAPI version of the RE-0887 input transformer
A pair of exclusive Litz wire 2503 output transformers
A pair of our potted CA-0252 discrete opamps
The impedance load switch was moved to the PCB and its front panel position replaced with a crowd favorite 80Hz High Pass Filter
The impedance load switch is default set to 450 ohms and does not affect level in Line mode
Phantom power is defeated when Line mode is selected
Sonically all of the changes add up to capturing a more 3D space surrounding the microphone. It appears more clear than the OG
version while also sounding more analog. Bigger, deeper, sweeter.
The Heider® FD312 H2 is a special and unique preamp module that stands out in today's crowded 500 series market. The preamp
stage has been carefully modeled after the preamps in the famous Wally Heider Recording Studio 4 console custom built by Frank
DeMedio circa 1972. The original pre's were stock 312 cards modified by DeMedio. Frank removed the AP2622 input transformer and
replaced it with a custom wound Ed Reichenbach RE-0887. The RE-0887 has a very special tonal quality with some of the most buttery
smooth mids you will ever encounter! This tone has been retained with our CA-0887.
To enhance this special preamp circuit even further, we chose to employ a stepped 'fader' and active booster stage, very
reminiscent of our popular 2-stage VP28 preamp. This is essentially the same booster circuit that was used in the early to mid
'70's vintage API consoles. In remaining true to the Heider® circuit, all AC coupling capacitors have been removed from
the audio path. We don't think coupling caps are evil, they are just not needed in this particular circuit. This fader booster
stage has 12dB of gain 'in hand', exactly like a real console. This allows for many different gain combinations. You can
crank the fader and reduce the preamp gain or in contrast, attenuate the 2nd stage and crank the preamp gain for some sweet,
additional harmonic content.
The original Heider/DeMedio preamp cards used stock AP2503 output transformers. With the desire to have something unique, we are
using our 2503-Litz wire outputs. The very same that we use in our Platinum line of preamps.
In trying to be loyal to the console signal path, both gain stages have a 2503-Litz output transformer. The first or preamp stage
output transformer provides +6dB of gain, blocks DC from the stepped fader and imparts a little more character into the overall
circuit, as compared to a 'direct' output.
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)
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