It is also compatible with the Heritage Audio Frame 8 and Rack 2 powered enclosures. The 6673 is a 4 band equalizer in a 1073 sized module, combining the mid band of the vintage 1066 module and an expanded 1073 mid band. This fact allows a more complex equalizing whilst at the same time maintaining the same sonic qualities. Vintage connoisseurs already know how sweet the 1066 mid band sounds and how well it complements the 1073´s one. Additionally the 6673 features three frequency´s options for the high shelf, as opposed to the fixed ones on both the 1073 and 1066, covering both. Special care has been taken in sourcing the correct components that ensure performance will be as close to a 1070s unit as it is possible nowadays. Custom polystyrene and film tone capacitors have been developed to closely match the Siemens Styroflex and Mullard Mustard types of the late 60s and early 70s. Custom input transformers have also been co designed with Carnhill Transformers´ Oxford factory to our special requirements. The Heritage Audio 6673 is entirely handmade in our facilities in Spain, employing the same old-fashioned wiring and soldering techniques of the 70s. All its circuitry is held into five plug in cards.