Crane Song Insigna 500 Series Tube 3-band EQ

The Cranesong Insigna is a 500-series module tube EQ designed by Dave Hill and comes from a long line of industry standard, high quality audio hardware.

The unit is based around a dual triode circuit with a 12AX7 tube, featuring 2 shelving EQs, a parametric band and a low and high pass filter set. 

The filters are both 24 dB/Octave with 7 frequencies each.

The high and low frequency bands are both shelving with 8 frequencies a piece.

The mid frequency band is a peak EQ containing 8 frequencies.

All three bands employ buffered RC circuitry in the negative feedback path around the tube amps.

The output stage features a shielded Lundahl high level line output transformer, all the stepped frequency

pots are high quality Grayhill series 56 Rotary Switches and Bourn pots for the gain.

The Frequencies

Let's have a closer look at the frequency ranges you'll get to work with.

The high pass filter ranges from 25 Hz to 150 Hz (25 - 40 - 50 - 60 - 90 - 120 - 150) and the low pass filter from 6kHz to 20 kHz (6 - 7.5 - 9 - 10.5 - 12 - 15 - 20).

The filters will give you enough power to clean up low rumble, tidy up the low end on LF centric instruments and control harshness at the top like guitars for example. We'll cover some more application examples a little further on in the manual.

The HF shelf gently ranges from 3.2 kHz to 20kHz (3.2 - 5 - 8 - 10 - 12.5 - 15 - 20) with the addition of an ultra high AIR band centred around 40kHz.

On the other side of the spectrum, the LF band shelves from an extremely low 10 Hz up to 200 Hz.

Straddling the middle, the MID peaking band deals with anything from 150 Hz to 7.2 kHz and is centred around a proportional Q (bandwidth).

All three bands give you +/- 12 dB boost and cut.