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
Distortion
- < 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)