Simple mixer project (one mic, one line inputs)


2003-09-03 12:17 pm
Most active speakers today have a small integrated mixer section... but sadly not my RCF ART310A which just have one input. Which is a bit short even when all I need is one speaker.

So I've been looking at compact commercial mixers and I'm not impressed with what's on offer. I got a A&H Zed-6 which is great but way too big. A particular dislike of mine is that most small mixers use an external power pack and aren't very robust.

What I wanted :

- compact and robust (something you can easily strap to a speaker stand);
- IEC 230VAC input;
- impedance balanced output;
- one mic preamp (for dynamic mics);
- one stereo line input summed to mono (for a phone, a computer, etc.).

I attach the schematic of what I'm considering:

- the mic preamp is based on the THAT1512. Gain control by a revlog pot (attached to the front plate above the level controls). It's followed by a level control and a buffer in front of the active summer.
- the stereo input is passively summed and dc coupled. The gain of the input buffer can be changed, to use it as an instrument input (an input buffer is thus required for high input impedance). It's followed by a level control and a buffer in front of the active summer.
-3 peak detectors are on board and can be assigned to various points (based on the ESP's website circuit).
- the power supply used a small 4w smps module with universal AC input to +/-12V.
- the whole thing fits into a hammond 1455n1601 (16*10*5 cm).

Sadly, there's not much room left on the endplates for a tone section.

A first attempt at a pcb is attached, just to show how it all fits.

If anyone has ideas on how to improve this thing (or spot an error), please do tell ;)


  • micpre.png
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  • micpreboard.png
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