Design Changes

Just after I finished the first PCB I moved to London to start a industrial year working at a pro audio repair shop. It was a great year, but it meant the project slowed down quite a lot as I had less free time. I also started the rethink some of the design choices.

I decided to change to virtual earth summing at this point as I wanted every individual channel to be switchable, as opposed to having just 2 groups of 4 channels hard wired to the 2 different buses. Although this could still have been done, it would have meant doubling the number of switch poles (due to needing to back-ground the resistors on a passive mix amp) and therefore increased the cost considerably.

I also reconsidered using a tube gain stage, partly due to my total lack of tube experience and the added cost of having a separate HT PSU.

I made this block diagram and started to plow on with the schematics.