48v phantom power from 12v power supply!?

fretless

fretless

New member
hi,

i own a boss br-1180 and was wondering how it is possible that this recorder with its ac adaptor delivering 12v is capable of providing 48v phantom power for its 2 mic preamps?!?

does anybody know?
does it really work or is this just some kind of hype and i don´t really get 2x48v but maybe some lower voltage?

thx for any ínsight!

fretless
 
The same way you can get 40,000 volts at the back of the cathode ray tube in your television set when the supply in your house is only 110V. Step-up-transformer.
 
I don't think they use a transformer. Most likely it is a DC-DC converter--simple oscillator working on high frequencies, which converts DC to AC, followed by a voltage multiplier, which converts AC back to DC, and then filtering stage. Very simple and much cheaper and smaller than a transformer.
 
Just to butress Marik's point, these DC to DC converters are (or at least use to be) available at Radio Shack. They take the form of a chip with generally three or four leads. If you are putting a good (read "no ripple") DC voltage on the input, you generally need no further filtering on the output. Some even come with a variable output, adjustable with a potentiometer. These chips are cheap. They cost all of $3-5 as I remember. For low current applications (under 1 amp) they can't be beat.

If you need to do this, make sure you know the current required as you may need to attach the chip to a heat sink.

Good Luck!

Steve
 
i was wondering this recently when looking at a friend's Tapco mixer which was running of 9 or 12 volts. it still sounds like cheating to me!
 
Step up transformer...gives you higher voltage but proportionately less current...you can have 10,000 volts running through you and not feel a thing...one volt can kill you theoretically.
 
Hi, Fretles.

Is it 12VDC or 12VAC?

If it's 12VAC, all it takes are a few capacitors and diodes to make a "voltage quadrupler" circuit, thus giving you a rectified +48V RMS. Filter and regulate that, and vo-la! You've got +48V phantom power.

If it's 12VDC, then they have to jump through a few extra hoops like Marik said. But, to answer your question, yes it's do-able.
 
But I belive its the other way arround...what you discribed was a rectifier...12VAC can be stepped up with a simple 4:1 transformer...a quadrupeler circut works on DC.
 
Darrin,

The voltage multiplyer works with AC only, so there is no reason to put additional transformer. Once again, if it is DC, you need to have an oscillator to convert it into AC, first.

Guitarlover,

We need to filter an output, otherwise you will clearly hear the oscillator frequency, even if it is beyond audible range, as it can create resonances and harmonics.
 
darrin_h2000 said:
But I belive its the other way arround...what you discribed was a rectifier...12VAC can be stepped up with a simple 4:1 transformer...a quadrupeler circut works on DC.
Click to expand...
It multiplies and rectifies. Here's a link to what I'm talking about: Voltage multipliers

You could use another transformer, but the diode/cap circuit's cheaper and commonly used for this type of thing.
 
there's a thread like this in another board, maybe the newbies one. it's called 'tiny stereo preamp' or something. can't find it right now but that's because it's 2:10am and i'm knacked!
 
Yes there is a behringer battery powered mixer...so that wouldnt wash because an inverter would be required to bump it up according to some only to be converted back to 48 volts DC to run those mics.;)


Im an electronics enginering technology grad from DeVry...hell I learned Multiplier circuts before the units on AC were taught to us. If I remember correctly...it was 10 years back.
 
darrin_h2000 said:
Yes there is a behringer battery powered mixer...so that wouldnt wash because an inverter would be required to bump it up according to some only to be converted back to 48 volts DC to run those mics.;)


Im an electronics enginering technology grad from DeVry...hell I learned Multiplier circuts before the units on AC were taught to us. If I remember correctly...it was 10 years back.
Click to expand...


i've just visited the behringer site and it's called the EURORACK MXB1002, however this baby only gives 18 v or 23 v phantom!!!

http://www.behringer.com/MXB1002/index.cfm?lang=ENG
 
Marik said:
Darrin,

The voltage multiplyer works with AC only, so there is no reason to put additional transformer. Once again, if it is DC, you need to have an oscillator to convert it into AC, first.

Guitarlover,

We need to filter an output, otherwise you will clearly hear the oscillator frequency, even if it is beyond audible range, as it can create resonances and harmonics.
Click to expand...

Please Note, I said "clean". Or at least I think I did. Either way, you're probably right. I'm used to working with applications that don't concern themselves with anything out of audible range. So, slap a few capacitors on the output and your off to the races! :D

Regards, Steve

PS The "tiny stereo preamp" thread is mine. It's over on The Rack. I'm the one who just made one for a portable application I have
 
DC-DC converters yes, super versatile wee things.

Aimtec are one of the main manufacturers and they are available in a vast range of power ratings from 1W up to many tens of watts and many different input and output voltage ratings.

I used two 1W devices to derive 10volts from usb 5V to power some guitar pedals (peeps are never more than 10mtrs from a rat or a computer!) .I had to use two because my local Maplin's did not have the 5V to 10V I needed so I had to have 2x 5in and series the outputs. The output is very clean and at least as well regulated as the input.

The ready availability of these converters no means that no longer do pedal/AI etc, makers need to supply a model specific wall rat. Two DC voltages should suffice, 12 and 24. AC rats of course will soon be outlawed in the EU.

Dave.
 
I take it that an AC "rat" is a plug pack (or wall-wart) that provides AC.

The more compelling question to my mind is, why did Dave feel the urge to resurrect an 8 year old thread :rolleyes:

Paul
 
PRHunt said:
I take it that an AC "rat" is a plug pack (or wall-wart) that provides AC.

The more compelling question to my mind is, why did Dave feel the urge to resurrect an 8 year old thread :rolleyes:

Paul
Click to expand...
Even more compelling is WTF is an eight year old thread still there! And Moresound didn't notice either.

Dave.
 
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