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SPL PQ 2050 Mastering EQ - Used  From SPL

Fully parametric stereo mastering-grade glory from SPL!


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What We Think

Condition: Used, Excellent


Serviced by Focal Naim America 09/13/2021:

SPL Knob, K22 Silver, metal w/ screw

Motorized potentionmeter - LMF Boost/Cut of Channel

OPX Boards (2)


Full report included in shipment.

Original components pictured in bag

Manufacturer's Description from SPL

Key features

• Pure analog, discrete Class A equalization circuitry

• Digital storability and total recall with motorized controls and 800 presets

• Constant Q and proportional Q modes, selectable per filter band

• 124 V internal operating voltage for clean, consistent audio

• Discrete SPL SUPRA op-amps with 150 dB dynamic range

• Channel link mode for stereo applications

• Master/slave unit link mode for surround applications or subgroup processing allows remote control of up to four PQs via optional remote unit (still in development)

• As with all SPL products, the PQ is conceived, designed and hand-built in Germany


Constant Q and proportional Q modes

Each frequency band consists essentially of two fully parametric equalizers: one for constant Q mode and one for proportional (or variable) Q mode, selectable per band. The PQ is the first equalizer to offer both modes, endowing it with double equalization power for demanding corrective and creative applications.

In constant Q mode, the selected bandwidth remains unaffected by the amplitude setting, making it the best choice for corrective applications (e.g. to eliminate unwanted frequencies). In proportional Q mode, the amplitude is reduced as the bandwidth is raised and vice versa. With the smallest bandwidth setting, the maximum amplitude reaches +/- 11.5 dB, while it is reduced to +/- 2.5 dB with the broadest bandwidth setting. The Proportional Q mode is better suited for creative, sound-shaping applications, as a bandwidth-related amplitude allows for sensible, musically suggestive operation – with raising bandwidths, higher amplitudes are increasingly less useful.



All variable controls are motorized and all keys are digitally controlled to provide the same programmability and repeatability of digital units. Individual settings can be stored in up to 800 presets.


Link mode

Channel 1 and 2 can be linked for coherent stereo operation and either channel can be designated as master. In link mode, coupled bands can be activated/deactivated simultaneously, while single bands may also be released from link mode if required for individual adjustment.


Master/Slave (unit link) mode

The PQ offers a Master/Slave mode for surround applications or subgroup processing, in which the settings on the master unit are precisely duplicated on the slave units. Thus the PQ is the first EQ system that provides up to eight channels for coherent analog equalization of surround recordings.


Remote Control Unit

SPL offers a remote control unit with an identical user interface to the PQ, which will be able to control up to four units—individually or in common.



A central display clearly indicates all information relating to preset, storage and control functions. The control logic is clear and intuitive without menu layers, guaranteeing quick and easy operation and a minimal learning curve.


Motorized potentiometers

All of the PQ‘s potentiometers are motorized to accommodate the channel link and unit link functions. The adjustment range of the Frequency, Bandwidth and Amplitude potentiometers is evenly dispersed throughout the 300-degree movement area, ensuring smooth and continuous adjustments and extreme operational security. The high resolution of each respective value (e.g. Q from 0.1-3.7, evenly distributed over 300 degrees) allows extremely precise adjustments as well as accurate repeatability.

We intentionally avoided unnecessary or confusing functions such as frequency range switching or frequency, bandwidth or amplitude multiplicators.

Important note: The motorized potentiometers should NEVER be manually moved or held while being controlled by the motors, e.g. in channel or unit link mode.



Amplitude settings are freely adjustable from -11.5 to + 11.5 dB. The lower range between 0 and 2.5 dB offers extremely high resolution, allowing delicate adjustments with maximum precision.



Each channel provides five fully parametric frequency bands covering 10 Hz to 28 kHz. Each band overlaps its neighbor by one octave and can be independently activated and deactivated.

The following frequency bands are provided:

LF (Low Frequencies): 10 Hz - 235 Hz

LMF (Low Mid Frequencies): 35 Hz - 720 Hz

MF (Mid Frequencies): 330 Hz - 7.1 kHz

HMF (High Mid Frequencies): 670 Hz - 16 kHz

HF (High Frequencies): 1.2 kHz - 28 kHz



Bandwidth is adjustable between 0.1 and 3.7 Q in proportional Q mode and between 0.9 and 15 Q in constant Q mode. The extremely high maximum bandwidth in constant Q mode enables tight, selective control in precision applications.


Illuminated keys

The PQ features illuminated keys that illuminate brightly when activated. The final software version will provide dimly lit keys (25% brightness) when deactivated for ease and security of operation. The current software version (240H) switches illumination off when keys are deactivated.


LF, LMF, MF, HMF and HF keys

These keys activate (key lamps lit) or deactivate (lamps off) the 10 filter bands.


Con. Q key

This key switches the 10 filter bands between proportional Q mode (lamps off) and constant Q mode (lamps off).

Please note: It is impossible to activate the “ON” for a specific band and the Con. Q button simultaneously. Please always press one of these buttons after another. 


About Manufacturer

Sound Performance Labs! Full Range of Analog, Tube, and Digital rack gear with an innovative twist. With their most famous transient designer product, SPL has quickly become a household name in both the recording and live sound arenas.


• Frequency Range: 10Hz - 40kHz

• CMRR (1 kHz, +34 dBu, Band 1-5 ON, B/C = 0 : › -82dB

• Transmission Bandwidth: (3 dB, Band 1-5 ON, B/C = 0): 10 Hz-100 kHz

• THD & N (@ 24dBu, Constant-Q) › 107dB

• THD & N (@ 24dBu, Proportional-Q) › 106dB

• Noise (unweighted, at 24 dBu, Band 1-5 ON, B/C = 0) - 91dBu

• Noise (A-weighted, at 24 dBu, Band 1-5 ON, B/C = 0) - 94dBu

• Noise (CCIR, at 24 dBu, Band 1-5 ON, B/C = 0) - 86dBu

• Harmonic Distortion:

        0,2% @ 1kHz/-30dBu

        0,05% @ 1kHz/-20 dBu

        0,01% @ 1kHz/0 dB

        0,002% @ 1kHz/+10 dBu

        0,0005% @ 1kHz/+30 dBu

• Input Inpedance: 20kOhm

• Max. Input Level: + 32,5dBu

• Output Inpedance: ‹ 600Ohm

• Max. Output Level: + 32,5dBu

• Power Consumption: max. 61W

• Fuses

        230 V/50 Hz: 3,15 Amp

        115 V/60 Hz: 6,3 Amp

• Dimensions: 482 x 177 x 311,5 mm / approx. 19“ x 7“ x 12,25“

• Weight: 15,2 kg / 33,5 lb

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