Raw State Decca EQ 1960s

Decca Passive Precision EQ

Re-racked 2025 by local LA Tech.

Amazing Condition - In Working, Smoke Free Studio

Unit is big! 3U - 24" deep

Description from website

Two channels of very special and rare Eq, based upon late 1960’s Decca ‘Tone Control’. These units appeared in their disc-cutting and duplication consoles, and were built by hand and in very limited numbers. In fact, every module is somewhat different!

Raw State has collected these Decca units over a period of 12 years; therefore, the total run is rather limited. In fact, only 10 chassis have been built.

The design is passive circuitry based upon the classic R – C – L components ( resistors, capacitors, large multi-value inductors ). As they are passive there was a need to build associated circuitry to correct insertion losses, match impedances and provide balanced input and outputs.

Raw State has spent considerable design and listening time to ensure the original units’ great quality was not compromised. With carefully matched input and output impedances to ensure the Eq characteristics are well controlled and musical.

A custom designed discrete Class A gain stage is used to restore gain to unity. 40 db of overall gain was needed. For good noise and sonic performance, the four input devices are selected for gain match and used in a parallel configuration.

Balancing is naturally by transformers, as it was felt the addition of audio transformers is so much a part of classic- sounding vintage equipment.

Marinair LI 31267/ T1442 input transformers with LL63RB vintage output transformers were used..

The power transformers are run in parallel to help reduce hum pickup, by positioning them to radiate their magnetic fields out of phase.

Careful selection and auditioning of components were carried out. This includes using audio grade solid aluminium capacitors and small value bypass caps. Signal wiring is Oxygen free, connectors are Gold Plated.

Typical Performance:

Shelving and Resonant ( Bell ) type Eq.

The low-frequency  Eq range extends from 12 Hz to 240 Hz.

The high-frequency Eq range extends from 1 kHz to 32 kHz.

Max. Boost and Cut 8 db. Switched in 2 dB steps.

Eq cut at position ‘R’ offers very deep notch filter.

Maximum level into 10K better than +26 dB @ 1 kHz

Noise ( Eq controls flat )  better than -83 dB unweighted / -88 dB with 10 Hz —-10 kHz filter

-3 dB Lf and Hf points better than 10 Hz — 40 kHz