Specs and Operating Characteristics:

Low Pass Filter
• filter slope 9dB/octave at zero resonance
• filter cutoff sweep range 160 Hz to 22kHz
• resonant peaking from 0 to +12dB

Hi Pass Filter
• filter slope 12dB/octave at zero resonance
• filter cutoff sweep range 22 Hz to 2700Hz
• resonant peaking from +3 to +15dB

"Bax" Tone Tipper EQualization Curves: see CURVES

Rear Connectors: Line input and Line output on card edge (xlr i/o on standard "500" racks)

Input Impedance
• nominal 11,000 Ohms Balanced

Max Input Level:
• +28dBu

Output Impedance:
• nominal 130 Ohms Balanced

Output Clip Level:
• +25dBm

Power Consumption:
• +/-15Vdc 75mA

CurvOmatic Filter/EQualization module (FT501):

The CurvOmatic module is a versatile set of high and low pass variable resonance sweep filters combined with a very sweet sounding version of Peter J. Baxandall's classic 1950 tone control circuit.

Used in combination these provide a surprising amount of tone carving and shaping capability that is unlike anything you can get from standard equalizers and cutoff filters. Each section (lo pass, hi pass and tone tipper) has a switch that bypasses or removes that section. There is a "hard" bypass "BYP" that connects the module input directly to the output.

The frequency sweep ranges on the hi and lo pass filters overlap from 160Hz to 2,700Hz, and covering the entire audio spectrum of 22Hz to 22,000Hz between them. The resonance controls vary from 3dB to 15dB of peak at the Hi Pass filter cutoff and 0dB to 12dB of peak at the Low Pass filter cutoff.

The ganged ToneTipper EQualization circuit is a non-shelving tone control which is very organic and natural sounding. Turn its knob clockwise to boost treble while attenuating bass, and turn counterclockwise to boost bass while attenuating treble. The advantage of this type of tone control is that the curves are smooth and continuous so the rise or fall of energy is consistent across the entire spectrum as opposed to a shelving type control that simply lifts up a plateau of energy in one part of the spectrum or depresses a flat valley in another.

Look at the CURVES... They explain a lot about this device and we'll get some audio samples up as we get more units in hand to sprinkle around.

The CurvOmatic is transformer-balanced in and out. The output is capable of driving loads as low as 300 Ohms, while the input can take very high levels without overloading. Internal operating level is very low, allowing for max boost without clipping. All five rotary controls are continuously adjustable for fine tuning.

Front Panel Features and Controls - top down:

Provides continuous control over resonance from none (fully anti-clockwise) to 12dB of peaking at cutoff (fully clockwise).

bypasses or inserts the filter into the signal path.

Sets the filter cutoff anywhere from 160Hz (fully anti-clockwise) to 22kHz (fully clockwise). With resonance turned fully anti-clockwise (no resonance) the filter slope is 12dB /per octave. With resonance added, the cutoff slope above the resonant peak becomes steeper as resonance is increased.

Provides continuous control over resonance from 3dB (fully anti-clockwise) to 15dB of peaking at cutoff (fully clockwise).

bypasses or inserts the filter into the signal path.

Sets the filter cutoff anywhere from 22Hz (fully anti-clockwise) to 2700Hz (fully clockwise). With resonance turned fully anti-clockwise the filter slope is 12dB /per octave. With resonance added, the cutoff slope below the resonant peak becomes steeper as resonance is increased.

Activates the tip equalization control.

Tone Tipper control, when active, is roughly flat in it's center 12 O'Clock position... meaning that as soon as this control is active it is doing something... and as it's turned clockwise from center it will tip high frequencies up while tipping low frequencies down. Conversely, as the tip control is turned anti-clockwise from center will tip low frequencies up while tipping high frequencies down. This done in a smooth organic sounding curve... see the CURVES

Engages CurvOmatic signal path and activates an orange LED when pointing up. Connects input to output for system bypass when pointing down.