The EQ531T is a 3 bands tube equalizer plus High pass filter, built around a dual triode, in the 500 series format.
The top and bottom bands are Baxandall shelving with 5 frequencies each,
The Midband is based on a multi-tap inductor, with 5 frequencies,
Each band and filter can be deactivated,
12dB boost or cut in each band,
Low shelf frequencies: 60, 100, 180, 270 and 450 Hz,
Midband frequencies: 240, 500, 1k1, 2k3 and 5kHz,
High shelf frequencies: 2.5k, 4k, 6k, 9k and 12kHz,
High pass filter continuously variable from 15Hz to 400Hz,
Transformer balanced output,
Bypass by hardware relay,
Available assembled or as a full kit (everything included).
More details here: EQ531T