The Tektronix Type E is a low-level differential amplifier plug-in for 500-series scopes. The sensitivity ranges from 50 μV/div to 10 mV/div. The input is an XLR connector feeding directly into the grids of a 12AX7 differential amplifier.
Despite the DC-coupled input stage, the Type E is an AC-coupled amplifier. It has front panel knobs for selecting the low-frequency and high-frequency cutoff. It achieves a 50,000 to 1 common mode rejection ratio. Maximum bandwidth is 60 kHz. It has seven tubes, three of which are on a shock-mounted subchassis.
The Type 53E/54E was introduced in 1955. Along with Types G and K, it was the first plug-in offered after, not during, the original 531/535 introduction in 1954. The nomenclature was revised after just a few months, to 53/54E. In 1959, when the A-suffix mainframes came out, all plugins dropped the "53/54". Type E was dropped after 1968; its replacement, Type 1A7, had been available for a few years.