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16  Using Arduino / Audio / Re: TL082 preamp: help please! on: October 16, 2013, 06:26:53 pm
biasing always confused me when i was first getting started.  im working on an online tool to help out with this:

it may or may not work, making webpages is not really my thing.  actually, using computers must not be my thing, considering i can no longer view much of anything on this webiste since they updated it.

basically, you take 2 equal value resistors, and connect one to 5V, the other to ground, and the juncture between them goes to the positive input of your amplifier.  the TL082 needs about 3V of headroom, so the +Vcc pin (postive powersupply) wil need more than 8V, and the -Vee pin (negative power supply) will need at least -3V.  otherwise they make different opamps that can go all the way to the rails, so you can just use +5V and ground as your supplies.
17  Using Arduino / Audio / Re: Problem using op-amp in audio system on: September 29, 2013, 01:53:15 am
the ts922 is a rail-to-rail opamp, whereas the tl072 is not.  this means that the tl072 can not amplify signals that get too close to ground or the powersupply rail, either at the input or the output (which happens in this circuit).   the ts922 also has a higher max output current.
18  Using Arduino / Audio / Re: i want to record audio in real time to matlab just record by any program on: September 27, 2013, 01:58:08 pm
its been a decade since i last did this, but here are some matlab links that seem to be useful:
19  Using Arduino / Audio / Re: Suggestions for Audio DSP? on: September 25, 2013, 01:14:24 pm
one other, completely different pathway, would be to get small computer and put a usb sound card on it that has the io you want.  a raspberry pi might get you most of the way there.
20  Using Arduino / Audio / Re: Suggestions for Audio DSP? on: September 25, 2013, 01:11:43 pm
i would also reccomend looking into devboards from the major manufacturers.  TI has some stuff, Analog has its sigmaDSP line which is pretty interesting.  it has a nice GUI for doing filters and such easily.  Freescale also inst bad.  if you want something quick, you might try looking into the old tonecore pedals from line6.  they have stereo in and out, and an onboard dsp and microcontroller.  otherwise you will have to roll your own.
21  Using Arduino / Audio / Re: Suggestions for Audio DSP? on: September 24, 2013, 02:22:53 pm
1. how many analog ins/outs do you want?  you mention mixing 32 channels, but im guessing those are digital channels.

2. what aspects do you want to control with the arduino versus do on the DSP processor?

3. what language do you want to use to program the DSP side of things?
22  Using Arduino / Audio / Re: i want to record audio in real time to matlab just record by any program on: September 24, 2013, 02:20:35 pm
you can use an arduino to capture sound, but matlab has a function which can capture straight from your soundcard, so you that would probably be a better route.  there are shields that can give you high quality audio from your arduino, but these are more work/more money that just using the computer. but, they might be good for a portable application.
23  Using Arduino / Audio / Re: Audio Sampling Rate on: September 11, 2013, 01:23:23 pm
200kHz is the reccomended fastest ADC clock speed, not the ADC sample rate.  the ADC needs at least 13 clocks to take a sample, so its more like 15ksps.  but, you can go faster with slight bit depth/resolution tradeoffs.  these are all documented here:

i find the 38ksps rate to be the sweet spot for best audio performance.
24  Using Arduino / Project Guidance / Re: Expanding the Repatcher on: August 14, 2013, 06:58:57 am
they do make shift registers that can switch between parallel to serial, and serial to parallel, but i dont think that helps in this case.  you need one shift register to hold a voltage, while the other shift register clocks the data in.
25  Using Arduino / Project Guidance / Re: Expanding the Repatcher on: August 13, 2013, 04:04:20 pm
you will want to change the code so the connection information is stored across a number of bytes.  so rather than put them all in a long, just do 4 bytes.  you then setup Pure Data to repack them, or just use them as they come in.
26  Using Arduino / Programming Questions / Re: Improving FHT resolution on: August 12, 2013, 11:30:56 pm
to sample slower, you can either setup the ADC to sample on a slower interrupt, or just use analogRead().  the latter is probably easier to get started with.  you can call analogRead(), and then put a delay in for the right amount of time.  be sure to comment out all the ADC setup code before using analogRead().
27  Using Arduino / Project Guidance / Re: Expanding the Repatcher on: August 12, 2013, 04:45:07 pm
this is possible, and shift registers are probably the way to go.  the only thing to watch out for, is that it will end up needing a lot of diodes.  each output needs a diode.  so if you make a 16 x 16 patch bay (and want to have 16 outs per row) you will need 256 diodes  the speed will be fine as well, it doesnt take much processing to scan the array.  look around for a project with shift registers and see what they used for code.
28  Using Arduino / Programming Questions / Re: Uncooperative code: FHT vs Display on: August 11, 2013, 09:23:22 pm
get rid of the lines:

TIMSK0 = 0;

and see if that helps.
29  Using Arduino / Audio / Re: Convert analog input from mic to decibels on: August 11, 2013, 04:05:24 pm
yes, this is possible, but you will need to calibrate your microphone in some way (at least if you want the decibels for comparison to other data).  you should look around and see if anyone has written an RMS function for arduino.  it wouldnt bee too hard to implement elsewise.  then its just 20*log(value).  i have a fast log(sqrt()) i can dig up if necessary.
30  Using Arduino / Audio / Re: Storing data in an audio channel on: August 10, 2013, 02:58:51 pm
i made a mod/demod for transmitting data over the audio channel in skype (which uses lossy compression).  but, i found that it would drop continuous tones more often than varying tones.  so making sure the signal is chaging a lot might help.  dont send lots of FF or 00.
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