The EQ531T is a 3 bands tube equalizer plus High pass filter, built around a dual triode, adapted to the 500 series of API*.

The tube, the midband inductor and the output transformer add a beautiful vintage colour to the EQ.

Just install it in your API* compatible Lunchbox^TM and start recording.

Highlights

• 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).

Controls

1: High frequency Sets the High shelf center frequency. 5 frequencies are available. The first position disables this band.

2: - dB + Sets the amount of cut or boost of the High shelf, up to 12dB.

3: Mid frequency Sets the Midband center frequency. 5 frequencies are available. The first position disables this band.

4: - dB + Sets the amount of cut or boost of the Midband, up to 12dB.

5: EQ IN Activates the EQ.

6: Low frequency Sets the Low shelf center frequency. 5 frequencies are available. The first position disables this band.

7: - dB + Sets the amount of cut or boost of the Low shelf, up to 12dB.

8: High pass frequency Sets the frequency of the High pass filter. Continuously variable from 15Hz to 400Hz.

9: HPF Activates the High Pass filter.

What's in the kit?

Absolutely everything!

• Passive components (resistors, capacitors, inductors),
• Output transformer
• Tube
• Active components (diodes, transistors, ...),
• Front panel elements (switches, potentiometers, knobs),
• Connectors, relay,
• PCB's,
• Front panel and side panels,
• All hardware

You bring the solder (use good quality solder, 1mm diameter max) and the Lunchbox.

Difficulty level

The EQ531T kit is a medium difficulty build.