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The Fredenstein F603 B is a high performance four band equalizer for tracking and mixing (Model B for Low Q=0.8).


The F603B features passive LC (Inductor/Capacitor) filters combined with a very short signal pass. The low and high frequency filters are shelving types, while the mid frequencies are band pass filters. Each shelving filter has four different frequencies while the band pass filters offer six. The active filter range is indicated by LEDs. To facilitate sound comparisons, a true “hard” bypass is available.

The gain range for each filter is +/- 16 dB. The F603B exhibits unrivaled silkiness, but at the same time an extremely detailed sound stage. The high power output stage with an impedance of less than 20 Ohms and a driving capability of up to +/- 200mA ensures no loss of performance with even the most demanding complex loads.


The Features

4-band equalizer for tracking and mixing

Low-Q=0.8 is ideal for overall sound sculpting

LC (inductor/capacitor) filters

Short, purist signal path

Silky, yet highly detailed sound stage

Low and high frequency shelving with 4 frequency centers

Two mid range peaking filters with 6 frequency centers

LED indicates the desired filter range

Each filter offers a +/-16 dB gain range

Filters are relay-switched for highest sound quality

High-power output stage drives even the most difficult loads

True hard bypass facilitates instant wet/dry comparisons

Requires compatible 500 Series chassis


The Specs

Frequency Response

20 Hz – 20,000 Hz, +/- 0.2 dB


< 0.01%

S/N Ratio

- > 90 dB at 0 dB Gain

Input Impedance

> 10 K Ohm

Max. Input Level

+ 24 dBu Balanced

Output Impedance

20 Ohm

Max. Output Current

- +/- 200 mA

Max. Output Level

+ 26 dBu Balanced

High Shelving Filter

- 9 KHz – 13 kHz in 4 Steps

High Shelving Gain

- +/- 16 dB

Hi Mid Band Pass Filter

- 1000 Hz – 5000 Hz in 6 Steps

Hi Mid Band Pass Gain

- +/- 16 dB

Hi Mid Filter Q

- 0.8

Low Mid Band Pass Filter

- 200 Hz – 800 Hz in 6 Steps

Low Mid Band Pass Gain

- +/- 16 dB

Low Mid Filter Q

- 0.8

Low Shelving Filter

 60 Hz – 230 Hz in 4 Steps

Low Shelving Gain

- +/- 16 dB

Power Consumption:

+/- 16 V, +/- 200 mA (600 Ohm Load)

Fredenstein F603B 500 Series Low-Q Equalizer Module

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