Useful and/or obscure information:       New Approaches to Improved Tonal Reproduction, Pt 1 db Aug 73 1, 2, 3, 4, 5 Tube Types for Audio Use Radio & Television News Nov 56 1, 2, 3, 4 New Transformer Design for Power Amplifiers Radio & Television News Nov 56 1, 2, 3, 4 Presto Recording Corp Amplifier Model 41 A schematic 1