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UNPLANNED DOWNTIME: 12th Oct 23:45

48V DC Phantom power for acoustic guitar

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jaymenonjaymenon Frets: 761
edited August 2022 in Acoustics
A couple of years ago, I rigged up a 9V DC phantom power supply for my acoustic guitar.

It just struck me though, most mixers (and indeed acoustic guitar amplifiers) afford +48 V DC Phantom power. 

Certain pick up manufacturers offer an 18V option which gives apparently more “headroom“

If someone were to make an internal pick up/microphone system that would utilise this, wouldn’t it give a lot more headroom/better sound?
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  • Danny1969Danny1969 Frets: 9752

    No, not really because headroom is only a problem if the gain ratio applied by the circuit exceeds the voltage rails of it's own circuit. 
    A pre amp circuit in an acoustic is more about converting the high impedance of the pickup into a lower impedance signal that can drive into a lower impedance input without losing tone caused by capacitive loading of the cable and other things. In general you want the input to be 10 X higher than the impedance of the source so the ouput imedance of a good pre amp is quite low.  
    Even with 9V .... which is actually 4.5V on a lot of pre amps as the circuit has to be biased at half the available voltage in order to swing either side there's enough clean headroom with 6dB or so of gain as well as the required impedance change. 
    www.2020studios.co.uk 
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  • crunchmancrunchman Frets: 10961
    I must say I like the idea of preamps that run on phantom power so you don't need to worry about changing batteries in the guitar.  Better for the environment as well as you aren't creating battery waste. 
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  • Danny1969Danny1969 Frets: 9752
    crunchman said:
    I must say I like the idea of preamps that run on phantom power so you don't need to worry about changing batteries in the guitar.  Better for the environment as well as you aren't creating battery waste. 
    You could Just use a DI box then, there are plenty that will run off 48V and achieve some of the  benefits   ....  or you could mod the guitar with a TRS jack and voltage divider to run the pre amp from phantom power .. the current draw needed is tiny 
    www.2020studios.co.uk 
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