It was on the way back from London. John Wood and I had stopped in the hotel at South Mimms for a coffee. It was about four o’clock on a Friday afternoon. We were sitting in a, then, modern, airy coffee shop. Mixer sales had dropped off. We were talking about the problems of making and installing the type of mixer we were making. All this contributed to the cost. If we could find a better way of making them, we could reduce the cost substantially. We went through the stages of manufacture. The wiring of each frame took about two man weeks. On a largish desk, the jack bay had to be wired on site. This would take another week or so. What we needed, was a frame that needed very little wiring. This led us to think about bus bars. If the frame just had a long row of printed circuit connectors, bussing the pins together would be fast.
So came the concept of each input channel being built as a complete unit, on one printed circuit board. The front panel would be a length of 1 3/4" section of extruded aluminium channel. Such channel would also ease the tolerance problems, being extruded and not cut. The printed circuit board would then plug into its own, single, connector at the back of the frame. Then, we discussed the jack bay. Much of this wiring was associated with inputs, outputs and the monitoring requirements. If we extended the single module per channel to the output as well, why not use the top part of each of these as a section of the jack bay? We must have been there for nearly two hours. We had drawn on all the paper napkins on our table, and from those tables near us.
That night, and on the Saturday and Sunday I worked on some designs. John had thought about the mechanics. By Monday morning, we had a rough design for a new range of mixers. We even had come up with a name in the coffee shop on the Friday - System 12. I decided that, with the exception of the input transformers, ICs, faders, knobs, and VU meters, we would get all the parts from the RadioSpares catalogue. Although there components weren’t always of the best quality, they did have every item in stock, and they came the next day. (Later, they were to change there name to RS Components, and their quality is now excellent.) Now, there were op amps available in small, 8 pin packages (DIL). Some experiments that week with op amps had convinced me of their value in professional audio equipment. We still had to use a couple of low noise transistors for the microphone amplifiers, but now, that was the only area where transistors were used. The op amps were quiet at line levels, had very high input impedance, very low output impedance, and could drive up to +18dB into 600 ohms. They did have two disadvantages. First this limit of +18dB, rather than the +20dB to +24dB we had previously worked to.
Second, their output was unbalanced. Again, we looked at what was happening in the States. Despite there having less dependable earths, they seemed to be managing with unbalanced signals. The decision to use unbalanced signals had advantages. The omission of transformers (except for mic input) meant less space, less distortion, and less cost. John was now busy, sessions and trips to New York allowing, on the engraving drawings, and choice of knobs. Three weeks later, the prototype was finished.
So came the concept of each input channel being built as a complete unit, on one printed circuit board. The front panel would be a length of 1 3/4" section of extruded aluminium channel. Such channel would also ease the tolerance problems, being extruded and not cut. The printed circuit board would then plug into its own, single, connector at the back of the frame. Then, we discussed the jack bay. Much of this wiring was associated with inputs, outputs and the monitoring requirements. If we extended the single module per channel to the output as well, why not use the top part of each of these as a section of the jack bay? We must have been there for nearly two hours. We had drawn on all the paper napkins on our table, and from those tables near us.
That night, and on the Saturday and Sunday I worked on some designs. John had thought about the mechanics. By Monday morning, we had a rough design for a new range of mixers. We even had come up with a name in the coffee shop on the Friday - System 12. I decided that, with the exception of the input transformers, ICs, faders, knobs, and VU meters, we would get all the parts from the RadioSpares catalogue. Although there components weren’t always of the best quality, they did have every item in stock, and they came the next day. (Later, they were to change there name to RS Components, and their quality is now excellent.) Now, there were op amps available in small, 8 pin packages (DIL). Some experiments that week with op amps had convinced me of their value in professional audio equipment. We still had to use a couple of low noise transistors for the microphone amplifiers, but now, that was the only area where transistors were used. The op amps were quiet at line levels, had very high input impedance, very low output impedance, and could drive up to +18dB into 600 ohms. They did have two disadvantages. First this limit of +18dB, rather than the +20dB to +24dB we had previously worked to.
Second, their output was unbalanced. Again, we looked at what was happening in the States. Despite there having less dependable earths, they seemed to be managing with unbalanced signals. The decision to use unbalanced signals had advantages. The omission of transformers (except for mic input) meant less space, less distortion, and less cost. John was now busy, sessions and trips to New York allowing, on the engraving drawings, and choice of knobs. Three weeks later, the prototype was finished.
The first Sysyem 12. On the beach"
Output and monitoring. Note the integrated patch panel at the top. This used 3.5mm jacks
The 8 track mounted in a Conran office desk
Input module
Livingston studios was the first customer. The main change they wanted was to have PPM meters in place of the VU meters. Installation now was a “plug in job”, and took about an hour.
System 12 Compact desk
