The EAR 864 preamplifier is designed to meet a wide variety of needs, from the most demanding of audiophiles to the professional seeking high quality monitoring equipment in the studio field. It is based on the circuit designs used in the highly successful EAR 834P phono stage and 834L line preamp, with a few additional refinements and features including balanced outputs and one balanced input, all coupled via high quality transformers. It has facilities for one phono input (MM/MC) and five line inputs, and offers a genuine tape monitoring circuit, making a total of seven inputs. A high quality volume control is fitted, as well as a panel mounted power switch. Input and output terminals are gold plated.

Power supply is a unique arrangement; a high quality toridal transformer feeds a double DC power supply, that provides the low-tension (LT) heater current, and the high-tension (HT) anode voltage. It is critical in a preamplifier that both the HT and LT supplies are pure DC, and free from AC ripple. This is the case with all EAR products, not just this preamplifier.