The 1975 issue 1 of The Audio Amateur is a technical treasure trove for the perfectionist, featuring elite speaker designs and advanced filter theory. Here are the highlights of this issue:
- A Proven Transmission Line Loudspeaker: Build a world-class four-speaker enclosure designed for the perfectionist. Using high-end KEF drivers and a specialized crossover, B. J. Webb details a transmission line system that achieves deep, extended, and non-resonant bass response that "thrown away" radiation designs simply can't match.
- Speaker Evaluation: Ear or Machine?: Part 1 of this series dives into the complex psychology of listening. Learn how physical and mental factors—and even the behavior of other people—can bias your perception of sound, and discover how to set up more reliable A-B comparison tests.
- A Test Bench Filter Set: Speed up your equipment checkups with these four "must-have" gadgets. This project includes a bias trap for tape recorders, a 20kHz noise filter, an ASA weighting network, and an inverse RIAA equalization network to help your measurements correlate better with human hearing.
- Op Amps for Audio: Active Filters: Master the art of frequency management with audio legend Walt Jung. This introductory guide explains the theory and practice of using modern op amps to build high-performance active filters that are easier to tune and more reliable than traditional passive designs.
- Multipath Revisited: Solve your FM reception woes. This follow-up and rebuttal provides a deep dive into the causes of multipath distortion and shows you exactly how to use an oscilloscope to detect and fix these signal-degrading reflections.
- Faith, Fidelity, and the Whatsis: Take a nostalgic tour of the audio "hi-fi go-round". Wailes Gray reflects on decades of audio trends—from early bass-reflex enclosures to the quadraphonic craze—finding that true musical satisfaction often lies in elegant simplicity.
- Classic Circuitry: The Audio Research SP-3A-1: Study the engineering of a modern masterpiece. This issue includes the complete schematic and parts list for the legendary SP-3A-1 preamplifier, a unit recognized even then as one of the few production pieces worthy of the "classic" label.
- Audio Aids: Discover ingenious DIY fixes from fellow readers, including a "Double Dub and Fader" for managing two tape recorders, tips for repairing snapped cartridge tapes, and instructions for building better tonearm pivots.
Table of Contents
- A Proven Transmission Line Loudspeaker: by B. J. Webb ................................................ 3
- Speaker Evaluation: Ear or Machine? Part 1: by Roger H. Russell ................................... 10
- A Test Bench Filter Set: by Fred M. Gloeckler, Jr. ........................................................... 16
- Op Amps for Audio: Active Filters, Part I: by Walt Jung ................................................. 22
- Audio Aids: by readers Hayward, Bayzer, Royer, and Gibbons ........................................... 28
- Book Talk: by Ronald H. Miller .......................................................................................... 31
- Faith, Fidelity, and the Whatsis: by Wailes Gray ........................................................... 34
- Multipath Revisited: by Fred M. Gloeckler, Jr. ................................................................ 36
- Classic Circuitry: The Audio Research SP-3A-1 ............................................................. 38
- Letters .................................................................................................................................... 40
- Ad Index ................................................................................................................................. 44
- Just Looking .......................................................................................................................... 45
- Classified ............................................................................................................................... 46