- Nov 10, 2006
- Norfolk - UK
I am working on a new design of tube mic pre that I hope is going to become a standard building block for my mixers. Two identical amplifiers, a mic input transformer and 12V heater regulator fit onto a single Eurocard which connects to the outside world via a nice meaty 32 way connector that we talked about on another thread. Each amplifier can have its gain set from 6dB to 40dB. The first amplifier plus the input transformer give up to 60dB mic gain and I am thinking of including tracking for a 1pole 12 way PCB mounting Grayhill switch for gain setting. The second amplifier has enough gain make up for the poor man's or posh man's EQ. I am currently using 1mm pins directly onto the PCB for the tube sockets as this saves having to mount tubes at right angles. This means the card can be made into a module 2.4 inches wide by attaching a suitable front panel and you can get exactly six of them into a standard Euro sub-rack. Mic gain and a simple EQ should fit on a 3U high panel but I have checked that a 6U front panel can fit without compromising the mechanical strength so that would give plenty of room for a three band poor man's EQ. At present I have been able to leave a 30mm blank space on the PCB immediately behind the front panel so there is room for panel mounted PCBs. I have a rough amplifier prototype working on the bench but the PCB layout is not yet complete and I need to thoroughly test this before freezing the PCB. So, at this stage I thought I would just mention what I am doing and put out a feeler to see if anyone might be interested in the PCB when it is done.