Tony Waldron, CADAC, UK

Back in 1994, CADAC Electronics PLC, decided to make sure that all of its products would meet the forthcoming EMC regulations. Since we knew nothing about EMC - or how to design equipment to meet the regulations - we looked for a suitable consultant. We chose Keith Armstrong of Cherry Clough Consultants because Keith had experience with audio system design, working for many years with the famous Neve company that designed and built similar high performance audio control systems for recording studios.

Our initial EMC training course from Keith helped solve many system problems that had plagued me for many years. Unfortunately, some of the CADAC engineers could not accept that their understanding of the grounding principles that they had  used for many years required updating. I had to put up with arguments about the principles of grounding for several weeks. Finally, I persuaded the management to use the EMC design techniques that we had learned for the design of our latest mixing console system called the F-Type, which was a low cost version of our very successful J-Type mixing console that was being used world-wide on musical theatre productions

When the final audio tests on the F-Type were complete, the results were totally amazing. We had become SO used to the fact that the microprocessor control circuits would inevitably ruin the audio noise figures, that the (almost complete) absence of digital processing noise was somewhat of a shock. Several engineers suggested that the computer control system was not working, which was why the noise figures were so good. The whole system was demonstrated to be fully working and that the total system noise had been reduced by 10dB

Subsequently, our audio testing showed that the RFI input & output filtering improved the audio performance so significantly, that customers would call me to ask what we had done to improve the sound quality. The very successful  J-Type was then redesigned using Keith's EMC system design techniques to bring it into line with its lower cost companion product.

When EMC design techniques are used at the beginning of a design, the overall cost is minimal. But we soon found that there was huge cost savings to be made during final testing and installation of our console systems. The time taken for console final test was reduced by 50%. During the installation of two of our consoles for a concert at the Royal Albert Hall, the staff complained about finishing too early and not getting paid triple time for working on the Sunday!

Anthony Waldron

Technical Manager, CADAC Electronics PLC, 1989 to 2014