The EM 1A from Tube Tech is a modular passive tube equalizer based on the original Pultec design, for use in the company's RM8 tabletop enclosure. The filter has a low frequency boost/attenuate section with 4 selective frequencies, a high frequency boost section with a variable bandwidth and 10 selective frequencies, and a high frequency attenuation section with 3 selective frequencies. The filter is placed directly after the input transformer thus eliminating noise from the amplifier.
The amplifier consists of two tubes (valves) in push-pull configuration (one ECC 83 as the pre-amp and phase splitter, and one ECC 82 as the output stage), and an output transformer. Both input and output are transformer balanced (600Ω) and fully floating. The in/out key switches the filter in and out without clicks, while the amplifier remains in the signal path. A red LED shows when output clipping is approached. The input and output transformers come with a static screen between the primary and secondary wirings.