During the late 70s \/ early 80s, experts such as Walter Jung and others published I.C. “cookbooks”.\u00a0 These were engineering publications that offered in-depth analysis of commercially developed integrated circuits and contained generic schematic diagrams of suggested applications.\u00a0 National Semiconductor, Motorola, and Signetics all published excellent product specification manuals.\u00a0 The 5532 chip was cheap, had very good performance, and could drive a balanced audio load to very high levels at low distortion, so we decided to make our own audio distribution amplifiers.<\/p>\n
As in the past, we submitted a work order to the excellent folks at the Physics Department.\u00a0 We provided a rough layout and our schematic, and the Physics department manufactured a blank circuit board per our specs.\u00a0We specified gold plated card-edge contacts and edge connectors to keep things “quiet” and used an off-the-shelf Vector brand enclosure for our boards.\u00a0 Each board had a master gain, and trim gains for each output.<\/p>\n
As in the past, the interns stuffed the circuit boards with the parts, soldered them in, and participated in testing their product.\u00a0 I made my one request:\u00a0 where possible, install the resistors with the color code facing the same direction, mount components with alpha characters\u00a0such that you can read them with the board oriented “up”.\u00a0 The above picture is a board I kept as a souvenir.\u00a0 Note that board was laid out as a 1 by 4. Despite the low cost of the parts, we stuffed this one for three outputs.\u00a0 I can’t recall why.<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" In the days before routing switchers, audio sources needing to appear on more than one mixer\u00a0had to be “split” through one of a couple of means.\u00a0 The absolutely cheapest and worst method was to simply wire them up in parallel. … Continue reading ![\"\"](\"https:\/\/johnfleetwood.com\/wp-content\/uploads\/2013\/04\/audio-DA1.jpg\" "\\"audio")
<\/a><\/p>\n