A multi-purpose PCB: Mic preamps, summing amps, line channels, mixer..?
- Thread starter ramshackles
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ramshackles
Well-known member
The very first module is almost ready:
http://groupdiy.com/index.php?topic=55189.20
It's an EQ...
The connector pinout/backplane has been designed and the first backplane PCB's are on the way...
The thinking now is not for a single 'do-all' PCB as it makes the amount of handwiring much more and hence the build less simple.
But, I would like to be able to offer something where you could get a simple mixer up and going with a very small number of modules and then have the ability to add preamps/eq's etc if desired...
At the moment, I have 1 eurocard which provides a line receiver & gain, fader and some auxes, and another eurocard which gives you a passive panpot and group-select.
The idea is to be very simple (something like 'The Box' or other 'desktop' mixers) and provide a choice of discrete or IC amps...
4 mono aux buses (but only 3 available on a single eurocard - aux 3/4 is selected via a switch. Saves a pot and knob and crucially real estate).
4 stereo mix buses (including the master).
So the absolute simplest mixer would be 2 modules on each channel (input module and switching module) and 4 summing cards...
http://groupdiy.com/index.php?topic=55189.20
It's an EQ...
The connector pinout/backplane has been designed and the first backplane PCB's are on the way...
The thinking now is not for a single 'do-all' PCB as it makes the amount of handwiring much more and hence the build less simple.
But, I would like to be able to offer something where you could get a simple mixer up and going with a very small number of modules and then have the ability to add preamps/eq's etc if desired...
At the moment, I have 1 eurocard which provides a line receiver & gain, fader and some auxes, and another eurocard which gives you a passive panpot and group-select.
The idea is to be very simple (something like 'The Box' or other 'desktop' mixers) and provide a choice of discrete or IC amps...
4 mono aux buses (but only 3 available on a single eurocard - aux 3/4 is selected via a switch. Saves a pot and knob and crucially real estate).
4 stereo mix buses (including the master).
So the absolute simplest mixer would be 2 modules on each channel (input module and switching module) and 4 summing cards...
gar381
Well-known member
ramshackles said:I updated the PCB connector layout to reflect the changes suggested here: 0V for the 5V connection, 58V and 48V GND.
I have not managed to find Jensen or Cinemag transformers which have the same footprint for both a 1:2 (or 3) mic transformer and a 1:1 line transformer...
Hi ramshackles
Just ran across this thread.. VERY NICE IDEA !!
Please double check your V- and output pins on your DOA sockets.
(I think you may have them flipped .)
All the best with this project!!
GARY
ramshackles
Well-known member
You are right - the first prototype I did of that design I had to install all the DOA's upside down :S...
I am now thinking that a single 'do-all' PCB is too complex and prone to mistakes, but a simple line-level mixer, with auxes and groups could be made with just 3 different module types.
You could then expand it to something more complex by adding your EQ's/Preamps/Compressors/whatever...
The first 4 in this table would be the 'base modules'
The summing PCB would be the most like a 'do-all' PCB as it would incorporate stereo/mono and probably balanced/unbalanced summing depending on how you put it together. Wiring it as a preamp wouldn't be too hard either, although I dont think I will document it. The summing PCB is based off that initial design you've quoted...
- the first prototype I did of that design I had to install all the DOA's upside down :S...I am now thinking that a single 'do-all' PCB is too complex and prone to mistakes, but a simple line-level mixer, with auxes and groups could be made with just 3 different module types.
You could then expand it to something more complex by adding your EQ's/Preamps/Compressors/whatever...
The first 4 in this table would be the 'base modules'
| Module | Concept | Design | Prototyping | Docs | On sale |
| Backplane | x | x | o | ||
| Receiving | x | o | |||
| Routing | x | x | |||
| Summing | x | o | |||
| Monitoring | x | ||||
| Easy69 (EQ) | x | x | x | o | |
| ISAish | x | o | |||
| S**tec-ish | x | o | |||
| Eurocard PS | x | x | o | ||
| External PS | o |
The summing PCB would be the most like a 'do-all' PCB as it would incorporate stereo/mono and probably balanced/unbalanced summing depending on how you put it together. Wiring it as a preamp wouldn't be too hard either, although I dont think I will document it. The summing PCB is based off that initial design you've quoted...
