An output transformer has its own frequency response, but the amplifier’s final response depends on the complete circuit. Negative feedback extends the bandwidth and improves low-frequency performance beyond what the transformer data alone suggests.
A reader asked why the power transformer isn’t mounted at 90° to the output transformers in my 1955 build, and whether that close spacing causes induced hum. Here’s why the layout works in practice.
Pair of Mullard 3-3 printed circuit boards designed to simplify assembly of the 1955 Model vacuum tube audio amplifier, including schematics and PCB layouts.
This document aims to serve as a guide for building the 1955 Gen2 vacuum tube amplifier. It can also be used for assembling the simplified wiring version, the 1955 Gen1.
In the original Mullard 3-3 design the operating point of the EL84 tube is highly dependent of the amplification factor of the EF86 tube.
It’s now been more than a year and a half since I first put the original 1955-model tube audio amplifier into regular use in my living room, and I’m pleased to report that it has operated reliably every day without a single breakdown. Over this period the amp has typically been in service for two
A new set of measurements for the Model 1955 Mullard 3-3 tube amplifier, including frequency response, phase shift, distortion, operating voltages, power consumption and sensitivity.