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#Welcome to the I2C-Midi Audio-Controler, driving I2C Digital Potentiometers (DIGIPOTS), I2C Bargraphs used as Vu-Meters, I2C Analog Voltmeters for controls, LCD Display for parameters and see current values, using Rotary-Encoders as commands.
Can be used for lot of Audio, Hifi, Home Theater, Music Intrumentation projects. Mine is for a 19" x 1U electric guitar preamplifier rack, using only valves through all the audio path (7 12AX7 twin Triodes + 3 EF86 Pentodes), from my own schematic diagram, to have "the best guitar valve preamp of the world". ;-)
This "controler unit" will be used to replace all the "old" analog potentiometers by Rotary Encoders to access to parameters, having virtualy any number of channels, storing them, restoring/recalling them, playing from Midi Pedals or any Midi external software, etc...
2016-06-26 : As long as the local image cache at GitHub still corrupted, I recommand you to follow the links to see the complete images and animated GIF directly yo my own WEB site, at bottom of these uncompleted local images in this Wiki page.
Digital Synoptic Diagram (logic)
Audio Path Synoptic Diagram (analog) :
The limitations are only the Raspberry-Pi-2 I/O limitations (number of available GPIO I/O, number of I2C available buses, quantity of I2C addresses available for each component to plug on the bus, etc...).
Few Digipots checked :
You can see moving the LED bargraph wen I turn a rotary encoder which is 0dB Centered and Logarythmic, as for a Bass/Treble adjustment :
http://www.youtube.com/watch?v=5XO7_utQYqM
Wires... wires...
2016-01-03 : new feature : you can stack several digipots in serial to make a kind of virtual "SUPERDIGIPOT", offering more steps (more resolution for LOG) and more resistance value.
2016-01-05 : you can have PARALLEL stacked digipots grouped/synchronised in only one SUPERDIGIPOT with only one human command from a single rotary encoder, offering a stereo volume (2 digipots) or a bigger 7.1 volume (8 digipots) as exemple, one digipot for each audio channel.
2016-01-16 : digipots and rotary encoders manage now an optional resistance value added between digipot B pin and the analog ground. All "dB" values are corrected regarding that.
2016-01-31 : found the time to integrate the Raspberry Pi 2 and 4 new PSU regulators modules into the rack. How the mechanic is more difficult than programming !
2016-03-23 : animated GIF showing the valves compression effect
2016-04-29 : just terminated the rack integration before to show it at Maker Faire Paris tomorrow Saterday April 29th and Sunday May 1st. Hoping lot of visitors and lot of hands to shake ! :-)
Taken few pictures of the box :
2016-05-12 : Replaced the "old" Raspberry Pi 2 by the new Raspberry Pi 3. Now, my preamp is directly connected to my WLAN (WiFi) at starting, and a Bluetooth chip could permit nice things later, wireless music, wireless guitar link, or wireless remote as example. Is there another valves guitar preamp with wireless SSH included ?
Any questions, corrections, suggestions to f6hqz-m@hamwlan.net
Have fun and good music !