Psidex Audio Laboratory PEQ-1 Manual

The PSIDEX PEQ-1 is a modern version of the famous "Pultec" equalizer popular during the
1950– 1960 period. Like the original, this design employs vacuum tube gain stages and a high
quality passive LCR equalizer network, long known for it's robust, low distortion performance.
This modern design offers lower distortion and noise over the original, in addition to more
frequency choices. A dual regulated high voltage power supply is used to provide plate voltage
along with a regulated heater supply. This power supply uses toroid magnetics to reduce magnetic
noise both internally and externally.
Modern features include conductive plastic potentiometers for high frequency boost and width
along with stepped switch controls for low frequency boost and cut and high frequency cut.
Polypropylene and polystyrene capacitors are used in the signal and frequency determining
circuits. The input and output line transformers are hand-wound for low capacitance and leakage
inductance and use modern high quality core materials and are magnetically shielded.
The makeup-gain line amplifier is a minimal feedback single ended Class A design. This approach
allows for a minimum parts count, which contributes to low noise and low distortion. Two vacuum
tubes are used in the amplifier. Signal input and output modes are independently switchable for
600 ohm balanced or high impedance, unbalanced, operation.
BOOST FREQUENCIES
L.F
20, 30, 60, 100, 150 Hz, 14 dB in 1 dB steps., shelf
H.F
1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18 kHz, 20 dB +/-1 dB peaking, continuously variable with
variable peak width.
CUT FREQUENCIES (ATTENUATE)
L.F
20, 30. 60, 100, 150 Hz, 18 dB in 1 dB steps., shelf
H.F
5, 10, 15, 20 kHz, 16 dB in 1 dB steps., shelf
DESCRIPTION
SPECIFICATIONS
EQUALIZER SECTION
1