Hi fellow modders, diy enthusiasts, and hackers. I am ramping up on ideas to build exactly what the thread title states... A 12v powered system that monitors pre-amp line levels and integrates with or adds on to minidsp 2x4.
Basically the flow is set up as such:
Line in -> minidsp 2x4 -> clip analyzer & protection uc (controls minidsp pot volume and clip LED status)
There would be two LED's... one for clip, as well as one for "protection mode active" when clipped for a certain length of time. A reset button would disable the protection mode, slowly bringing volume back up over several seconds. (2 status leds, 1 reset button) Or, the system could be fully automatic and skip the reset button.
Clip warning sensitivity will be input with a potentiometer or programmed in the sketch, same for protection delay. (2 possible pots)
I am going to be using arduino uno as the clip analyzer & protection control unit. I have seen that people are using arduino with a DAC to control the minidsp volume pot, so that is the method of protection. Here is a link to the DAC setup I plan to use.
An optional neat addition would be a simple rms VU meter to gauge minidsp output, calibrated closely to minidsp 2way advanced s/w level meters. With arduino already receiving audio in, this seems easy enough, though I am unsure if it would require some kind of FFT... For stereo down to 20hz I am not sure if the arduino uno can handle it, so it may just test for voltage levels approaching 0 or 5v (0V line level centered at 2.5V at arduino analog input). Here is a link to a possible method for arduino audio input.
I would love to know what you all think, or if you know any tricks to communicate directly with the minidsp? Aka if one could communicate digitally from minidsp <-> arduino it would seem to make this very, very easy! I2C?
Basically the flow is set up as such:
Line in -> minidsp 2x4 -> clip analyzer & protection uc (controls minidsp pot volume and clip LED status)
There would be two LED's... one for clip, as well as one for "protection mode active" when clipped for a certain length of time. A reset button would disable the protection mode, slowly bringing volume back up over several seconds. (2 status leds, 1 reset button) Or, the system could be fully automatic and skip the reset button.
Clip warning sensitivity will be input with a potentiometer or programmed in the sketch, same for protection delay. (2 possible pots)
I am going to be using arduino uno as the clip analyzer & protection control unit. I have seen that people are using arduino with a DAC to control the minidsp volume pot, so that is the method of protection. Here is a link to the DAC setup I plan to use.
An optional neat addition would be a simple rms VU meter to gauge minidsp output, calibrated closely to minidsp 2way advanced s/w level meters. With arduino already receiving audio in, this seems easy enough, though I am unsure if it would require some kind of FFT... For stereo down to 20hz I am not sure if the arduino uno can handle it, so it may just test for voltage levels approaching 0 or 5v (0V line level centered at 2.5V at arduino analog input). Here is a link to a possible method for arduino audio input.
I would love to know what you all think, or if you know any tricks to communicate directly with the minidsp? Aka if one could communicate digitally from minidsp <-> arduino it would seem to make this very, very easy! I2C?
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I've been making some progress...
https://vimeo.com/108770161
I ditched the idea of FFT, using straight voltages (pulled the internal ADC voltage reference down to 1.1V instead of 5V for better resolution). Taking 48 samples across 5ms to get the highest value, and the LEDs are lit logarithmically.
The clip light comes on before actual clip, and the protection mode is enabled if the audio signal reaches the "maximum" or clip... which is still set to about 300 out of 512 possible adc steps. Instead of using a pot to trim/adjust the max input values I am just doing it with software.
Protection mode adjusts the volume down (not immediately but with a delay) and once the audio is no longer clipping (after a few seconds of wait time), the audio is brought back up to normal levels. I used a simple RC filter and an interrupt library to do a very simple DAC (from the link above).
For audio input, I somewhat matched what can be found here: Arduino project: Stereo Peak Program Meter - APC
..with the exception of larger caps and resistors on the input.
Next step is to test with minidsp, and solder it up to the protoboard.
https://vimeo.com/108770161
I ditched the idea of FFT, using straight voltages (pulled the internal ADC voltage reference down to 1.1V instead of 5V for better resolution). Taking 48 samples across 5ms to get the highest value, and the LEDs are lit logarithmically.
The clip light comes on before actual clip, and the protection mode is enabled if the audio signal reaches the "maximum" or clip... which is still set to about 300 out of 512 possible adc steps. Instead of using a pot to trim/adjust the max input values I am just doing it with software.
Protection mode adjusts the volume down (not immediately but with a delay) and once the audio is no longer clipping (after a few seconds of wait time), the audio is brought back up to normal levels. I used a simple RC filter and an interrupt library to do a very simple DAC (from the link above).
For audio input, I somewhat matched what can be found here: Arduino project: Stereo Peak Program Meter - APC
..with the exception of larger caps and resistors on the input.
Next step is to test with minidsp, and solder it up to the protoboard.
I have used a DAC to control the miniDSP volume. I found that it was not good as a volume control - the range is too limited. If you want to use it only for volume reduction in response to clipping, that would be OK.
I used a 12-bit DAC that is available on a $5 breakout board that can be purchased at a variety of online stores like Sparkfun and Adafruit:
https://www.sparkfun.com/products/8736
It's very easily controlled via I2C and 12 bits gives you fine control. It will have extra voltage output capability that you don't need, but with 12 bits you can afford to just throw a couple bits away and use only the 0-3.3V range out of 0-5V.
There is some more info on this in a build thread of mine on this forum, here:
http://www.diyaudio.com/forums/mini...-remote-volume-off-control-3.html#post4006036
I used a 12-bit DAC that is available on a $5 breakout board that can be purchased at a variety of online stores like Sparkfun and Adafruit:
https://www.sparkfun.com/products/8736
It's very easily controlled via I2C and 12 bits gives you fine control. It will have extra voltage output capability that you don't need, but with 12 bits you can afford to just throw a couple bits away and use only the 0-3.3V range out of 0-5V.
There is some more info on this in a build thread of mine on this forum, here:
http://www.diyaudio.com/forums/mini...-remote-volume-off-control-3.html#post4006036
Thanks charlie! I had actually checked out your thread before doing some preliminary research. I am going to see if I can't just get the super simple DAC to work, just a 10k resistor to pin 10 and a .1uF cap to ground, with the DAC output in the middle.. Just a simple RC filter. The trick is getting a higher frequency PWM with the TimerOne library. If it works, I will be able to save myself a few dollars and an extra board.
Unfortunately I don't have an oscilloscope to test, but it did appear to be working with just my multimeter. And yeah, I don't so much mind if I am not able to reach full attenuation... This is just to quiet things down if a drunk DJ thinks he can crank the levels for more star power
Unfortunately I don't have an oscilloscope to test, but it did appear to be working with just my multimeter. And yeah, I don't so much mind if I am not able to reach full attenuation... This is just to quiet things down if a drunk DJ thinks he can crank the levels for more star power
Hey Charlie- can you let me know which pins you hooked your DAC up to? The datasheet is not really that descriptive, and if I test continuity between grounds the way it seems it should be labeled, it is not coming out right.
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I feel like the top left pin in the diagram should be 1, the bottom left pin should be 14, top right 15, bottom right 28. Can you confirm that?
Thanks in advance!
I feel like the top left pin in the diagram should be 1, the bottom left pin should be 14, top right 15, bottom right 28. Can you confirm that?
Thanks in advance!
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