Hi all,
I've seen several older threads on this topic, but none quite get to this idea.
Like several others, I'd like to be able to provide phantom power via bettery to those that require 48v.
There are several schematics which are designed with this in mind, but they seem to involve essentially building a voltage converter. I was wondering if I could do something really simple like connect a decent 12v battery and a 12v to 48v step up converter and just wire that to the pins of an XLR cable.
Am I missing something here?
(And in case it isn't obvious, I'm definitely not an electrical engineer. I know enough to have built a bunch of PA systems and even made some portable ones thanks to batteries and voltage converters, but this is a step beyond some of that.)
This is for live use in a rock setting, so it doesn't have to be 100% noise free. I just want it clean enough and to ensure I don't do something stupid that might destroy a mic I actually like.
Thanks!
I've seen several older threads on this topic, but none quite get to this idea.
Like several others, I'd like to be able to provide phantom power via bettery to those that require 48v.
There are several schematics which are designed with this in mind, but they seem to involve essentially building a voltage converter. I was wondering if I could do something really simple like connect a decent 12v battery and a 12v to 48v step up converter and just wire that to the pins of an XLR cable.
Am I missing something here?
(And in case it isn't obvious, I'm definitely not an electrical engineer. I know enough to have built a bunch of PA systems and even made some portable ones thanks to batteries and voltage converters, but this is a step beyond some of that.)
This is for live use in a rock setting, so it doesn't have to be 100% noise free. I just want it clean enough and to ensure I don't do something stupid that might destroy a mic I actually like.
Thanks!
You mean a Voltage quadrupler 4*12=48V and of course there are several approaches to accomplish this.
The step up converter should work but there is always the switching HF noise question if it is SMPS or the like based.
As mics consume very small currents (7mA) , You must make sure the converter used works / starts with these. Some only work with higher currents say 100mA threshold.
Bear in mind there are several mixers which use the op-amp supply to provide 30V (15+15) or even 24 (12+12) for phantom power and they work.
Don't forget the coupling capacitors and the 6.8K resistors and You should be fine.
Try !!
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At least you will need two well-matched 6.8 kohm (or 6.81 kohm) resistors between the 48 V supply and the XLR. It could well be that you also need some filtering to get rid of any ripple coming out of the converter. The converter has to be able to work with a very light load without switching into a special mode that produces audible frequencies.
Can the microphone amplifier handle large common-mode voltage jumps without damage? If not, you may need to add some sort of protection circuit after the AC coupling caps.
Besides a microphone and a phantom power supply, you will need something that processes the microphone's signal. If that last circuit is not designed to have a 48 V DC phantom supply voltage at its inputs, you will need to insert something that blocks the DC while passing the AC audio signal from the microphone. Hence MAAC0's recommendation to use coupling capacitors, a.k.a. DC blocking capacitors. I wonder if that is sufficient, or whether you also need a couple of clamping diodes.
Have you got any information about the microphone preamplifier you want to use?
Have you got any information about the microphone preamplifier you want to use?
You cannot convert 12VDC to 48VDC without an oscillator. Any Dc -DC converter like Amazon.com: SMAKN Waterproof DC/DC Converter 12V (10-30V) Step UP to 48V/4A 192W Power Supply Module: Home Audio & Theater
is an oscillator +transformer +rectifier +filter.
Phantom power needs to be very clean and it is unlikely the raw output from this module is that clean, however, the noise may be super-audible, above 20KHz, so that the microphone pre-amp may do the filtering for you. In any case, I would add more filtering. This module does have a metal shield which is another path for the switching noise getting into your audio.
PS, note that a 48V@4A converter may demand over 16 Amps at 12vdc, as it starts up, and may not start up if the current from the 12V is limited to less.
is an oscillator +transformer +rectifier +filter.
Phantom power needs to be very clean and it is unlikely the raw output from this module is that clean, however, the noise may be super-audible, above 20KHz, so that the microphone pre-amp may do the filtering for you. In any case, I would add more filtering. This module does have a metal shield which is another path for the switching noise getting into your audio.
PS, note that a 48V@4A converter may demand over 16 Amps at 12vdc, as it starts up, and may not start up if the current from the 12V is limited to less.
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What is an in-decent battery?
"DC/DC Converter 12V (10-30V) Step UP to 48V/4A 192W"
Near 200 Watts for 30 bucks is cheap. Suspiciously cheap.
4 AMPS will support four hundred Phantom mikes. Do you have that many?
As said, it may have start-up problems unless the battery is very powerful.
The intended applications are mostly motors. Motors will eat very ugly "DC".
Yes, we know. You're missing the point here. The 48V power supply will capacitively couple up to a 48V spike into the preamp's inputs when you turn it on and off.
Use four 12 volts batteries in series - 48 V?
Your initial question basically says it: "There are several schematics which are designed with this in mind, but they seem to involve essentially building a voltage converter. I was wondering if I could do something really simple like connect a decent 12v battery and a 12v to 48v step up converter and just wire that to the pins of an XLR cable."
... how can I avoid converter by using a converter... ???
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Your initial question basically says it: "There are several schematics which are designed with this in mind, but they seem to involve essentially building a voltage converter. I was wondering if I could do something really simple like connect a decent 12v battery and a 12v to 48v step up converter and just wire that to the pins of an XLR cable."
... how can I avoid converter by using a converter... ???
//