ZeroZ30o dit: also, are the FACE and BEAST capes meant to be expansions to the bela or are they added on top of the beaglebone black directly? In either case, is the sampling rate for them the same? And is it possible to have more inputs than outputs on them instead?
FACE and BEAST can work with the Bela cape but do not require it.
Number of I/O is fixed: 4in 8 out for the FACE, 8 in 16 out for the BEAST
LiamDonovan >Phantom power is only required by certain microphones.
I found a mic I'm interested in that requires phantom power -is the bela able to supply this or do I need some special kind of wiring for power on top?
Edit: the data sheet is not specified but it's a condenser mic with no other power sources, so I assume it must use phantom power?
ZeroZ30o Edit: the data sheet is not specified but it's a condenser mic with no other power sources, so I assume it must use phantom power?
maybe it is an electret condenser and it only requires plug-in power (2.5V) ? The latter is provided by the Bela cape, while the Bela Mini provides 3.3V (which is normally just fine), however both will require you to install an external resistor.
giuliomoro How much voltage can the bela supply for each microphone?
And is there a recommend output impedance range for microphones plugged in?
What happens if the output impedance of the microphone is too high/low for it?
ZeroZ30o How much voltage can the bela supply for each microphone?
2.5V or 3.3V. So that is really only good for electret capsules that require "plug-in" power
ZeroZ30o And is there a recommend output impedance range for microphones plugged in?
the microphones will have a recommended minimum load impedance. The audio inputs have 20k ohm input impedance.
ZeroZ30o What happens if the output impedance of the microphone is too high/low for it?
It's the other way round: "what happens if the input impedance of the device is too high/low for the microphone?" It depends on the mic and it normally happens only if the input impedance of the device is too low. The effects could be a combination distortion, change in the frequency response, low volume.
giuliomoro So, I've found a microphone with 2.2k Ohm impedance. So if I understood right this is fine, since the bela's inputs have 20k impedance which is way higher than 2.2k? Or is it the other way around?
that should be fine. Does it mention the minimum load impedance?
giuliomoro Not that I can find, no -in fact it only says "Impedance: 2.2k" and "Power: 3v" aside from the sensitivity and the frequency response range
it's going to be fine.
giuliomoro So if I plug in microphone's jack outputs to the bela I must also add an external resistor (if the microphone requires phantom power)? If so, how?
For speakers, I'm assuming the bela can't supply their power, is this correct?
Is there a recommended resistance for speakers (should it be as low/high as possible, or close to a certain value?)?
Thanks again!
ZeroZ30o So if I plug in microphone's jack outputs to the bela I must also add an external resistor (if the microphone requires phantom power)? If so, how?
Yes, to provide plug-in power (not phantom). How you fit it depends on your configuration. It could involve a bit of (careful!) soldering on the Bela cape.
ZeroZ30o For speakers, I'm assuming the bela can't supply their power, is this correct? Is there a recommended resistance for speakers (should it be as low/high as possible, or close to a certain value?)?
You can drive passive 8ohm(no lower than 8ohm) speakers directly from the on-board amplifiers, which can provide 1.1W(max 1.1W) (though these will only work if Bela is powered through the barrel jack). If you need different/more powerful speakers, they will have to be externally powered.
giuliomoro So regarding the microphone, which specifies that it is "plug and play, no need for an external power source", do I need to worry about anything extra?
The impedance and voltage are also mentioned: 2.2Ohm and 3V. Nothing else.
Knowing all that, if I only connect these microphones to the bela, will it be able to handle them correctly? If so, how many?
After that I should be set for hardware specs since I'm already set for speakers. Thanks again by the way.
ZeroZ30o do I need to worry about anything extra?
by the sound of it, they should be fine, but I cannot be sure if I don't see the datasheet.
ZeroZ30o 2.2Ohm
That is probably 2.2k ohm?
ZeroZ30o 3V.
That is weird, what is that meant to be?
Can you send a link to the microphone page?
ZeroZ30o If so, how many?
There are two audio inputs, so two microphones, I suppose.
giuliomoro You can drive passive 8ohm(no lower than 8ohm) speakers directly from the on-board amplifiers, which can provide 1.1W(max 1.1W) (though these will only work if Bela is powered through the barrel jack).
Forgot to mention: this powered output is only available on Bela (not Bela Mini)
giuliomoro Here is the "datasheet", that is all the info available on amazon's description of the microphone:
https://i.imgur.com/Bqb0Zdv.png (it's in French though)
The microphone itself is called "XIAOKOA PC condenser microphone"
Thanks for the rest though
Yes it will be fine. Use a 3k3 resistor from 3.3V (pin P9_03) to the input your mic is connected to.
giuliomoro I don't have the bela yet, and I'm not very familiar with how the jack-to-whatever cable looks so I'll have to ask for either pictures or again when I do have it
Sure, I can send some pictures when the time comes. You will need to buy a 3k3 resistor (they typically are very cheap, for instance you can get 100 for less than 1£ here http://cpc.farnell.com/unbranded/mcf-0-25w-3k3/resistor-0-25w-5-3k3-pk-100/dp/RE03809?st=3k3%20resistors ).
giuliomoro I want to connect loudspeakers to the Beast. The loudspeaker outputs on the starter kit work fine into my 16Ohm speaker - would their circuits be available or might you have a recommendation for a similar speaker amplifier that would run off 5V?
Hmmm maybe this is not the best thread for this. See relevant details about your issue here .
