SP502 - Preamplifier TK Audio - Free user manual and instructions

USER MANUAL SP502 TK Audio

500-series Class A preamp

1K 35 40 45 50 55 30 25 20 15 60 65 70 Gain -30 A HPF Sat Pol Dir In Output Hi-Z SP502

SP502 is a new single slot 500-series preamp with a unique hybrid design including both vintage and modern circuits.

A new transformerless input stage forms a clean and transparent front-end, together with the two selectable output stages you can get the low mid punch and thick sound associated with British Class A from the early 70's as well as a more modern clean tone from the 80's and 90's. SP502 is also equipped with a saturation stage that can be selected to add some extra harmonics to the signal. The sweepable HPF from 30Hz to 400Hz allows precision crafting of the low end.

If you select DI direct mode the Hi-Z input will be feeded directly to the output stage without passing the preamp stage (the saturation circuit and HPF can still be inserted).

Together with the vintage Class A stage activated you'll get a very nice discrete sound path for bass recording with lots of character.

By activating the saturation circuit the THD will raise to around 1% and add more color to the sound.

The DI gain from input to output is +15dB in direct mode.

Always lower the output level when you activate or deactivate the 48v phantom power to avoid loud clicks and pops!

graph LR
    A["+48v phantom power"] --> B["Hi-Z on"]
    B --> C["Pad"]
    C --> D["+15-70dB Gain Switch"]
    D --> E["DI-direct"]
    E --> F["Saturation"]
    F --> G["HPF"]
    G --> H["Output level"]
    H --> I["Class-A"]
    I --> J["Polarity"]
    K["+48v phantom power"] --> L["Hi-Z on"]
    L --> M["Pad"]
    M --> N["+15-70dB Gain Switch"]
    N --> O["DI-direct"]
    O --> P["Saturation"]
    P --> Q["HPF"]
    Q --> R["Output level"]
    R --> S["Class-A"]
    S --> T["Polarity"]
    U["+48v phantom power"] --> V["Hi-Z on"]
    V --> W["Pad"]
    W --> X["+15-70dB Gain Switch"]
    X --> Y["DI-direct"]
    Y --> Z["Saturation"]
    Z --> AA["HPF"]
    AA --> AB["Output level"]
    AB --> AC["Class-A"]
    AC --> AD["Polarity"]

Gain control. Phantom power on indicator. Phantom power on/off. -30dB input pad. -30 48V HPF 30-400Hz, 12dB/oct. Activates class-A output stage. A HPF on/off. Saturation on/off. Saf Output polarity flip. Pol Direct DI in/out. Dir Output level. DI input (through pre amp) in/out. In HI-Z DI input 1Mohm. SP502

Specifications:

Power requirement: +130mA / -130mA

Input impedance: 2400 ohm

Instrument input impedance: 1Mohm

Max output level: electronically balanced +25dBu, Class A +24dBu

DI direct gain: +15dB

THD+N @ +20dBu electronic balanced output: 0,0008%

THD+N @ +20dBu Class A output: 0,007%

THD+N @ +20dBu saturation active: 0,9%

Frequency response electronic balanced: -0,6dB @ 80kHz

Frequency response Class A: -0,5dB @ 20kHz

The output transformer is only used when Class A is selected and is normally terminated with a 600 ohms resistor to get a flat frequency respons in Class-A.

If the preamp has Class A selected and is connected to gear with 600ohms input impedance you should remove the termination jumper as the signal will otherwise loose hi frequencies and get overheated.

Close-up of a green printed circuit board with capacitors, resistors, and multicolored wires (no readable text or symbols)