48vdc out of 12vdc?

[imloggedin]

Im trying to build a power supply for a hamptone preamp im making. So im searching digikey for transformers trying to figure out a cheap way to make a 24/48 power supply. OVERWHELMING! anyway, i looked at the wall wart on my yamaha i88x and its 12vdc output. how do they make 48vdc from that?????

 

[skipwave]

There are ways to ramp up DC voltage to higher voltages. The one that springs to mind is a Charge Pump.

http://en.wikipedia.org/wiki/Charge_pump

Many condenser microphones use some implementation of these to ramp the 48VDC phantom power to a higher capsule polarization voltage in the 60-80 range.

However, you probably cannot get very good performance at the current draw of the hamptone JFP design. You would be better served to find a 24VAC wallwart, then internally regulate it with a pair of LM317 regs, one for the 24VDC and the other with a voltage doubler in front of it to get 48VDC.

Schematic Link (PDF)

 

[guavatone]

re. http://www.diyfactory.com/data/TKpowersup.pdf

Does TK's 48 PS need a ground connection on below the reg?

It's grounded on the trippler side, but I would think you would need ground refereence on the reg output.

 

[Tekay]

I missed the ground symbol :? feed the ground to the neg side of the 10uF / 50v below the 48v regulator

 

[gyraf]

Sony makes a small module (for video recorders?) for 12V>48V - used by e.g. Kev..

Jakob E.

 

[tk@halmi]

Murata/CD Technologies fabricates DC/DC converter that make 24V, 48V and 72V out of 12V. 3W max. I have used the 5V input version to get phantom power from DC heater supply of tube amp. Must add RC filter to output though. Should cost $15 or less.
Part#: NMT1272SC

 

[rolo95]

[quote author="tk@halmi"]Murata/CD Technologies fabricates DC/DC converter that make 24V, 48V and 72V out of 12V. 3W max. I have used the 5V input version to get phantom power from DC heater supply of tube amp. Must add RC filter to output though. Should cost $15 or less.
Part#: NMT1272SC[/quote]
http://www.mouser.com/Search/Refine.aspx?Keyword=580-NMT1272SC

 

[SSLtech]

[quote author="rolo95"][quote author="tk@halmi"]Murata/CD Technologies fabricates DC/DC converter that make 24V, 48V and 72V out of 12V. 3W max. I have used the 5V input version to get phantom power from DC heater supply of tube amp. Must add RC filter to output though. Should cost $15 or less.
Part#: NMT1272SC[/quote]
http://www.mouser.com/Search/Refine.aspx?Keyword=580-NMT1272SC[/quote]
Am I mis-reading that, or is it a negative-24 Volt output? -Shouldn't he want a positive-48 Volt output?

Keith

 

[jdbakker]

[quote author="SSLtech"][quote author="rolo95"][quote author="tk@halmi"]Murata/CD Technologies fabricates DC/DC converter that make 24V, 48V and 72V out of 12V. 3W max. I have used the 5V input version to get phantom power from DC heater supply of tube amp. Must add RC filter to output though. Should cost $15 or less.
Part#: NMT1272SC[/quote]
http://www.mouser.com/Search/Refine.aspx?Keyword=580-NMT1272SC[/quote]
Am I mis-reading that, or is it a negative-24 Volt output?[/quote]
Blame marketing. The part is aimed at the telco sector, where they traditionally use positive ground in many circuits. The input and output are fully isolated, so you can connect it any which way you like.

[quote author="The Output Voltage Configuration section of the datasheet"]Although the output is described for negative rails, the input and output circuits are iternally isolated hence positive rails can also be generated, or a mixture of positive and negative. The output +VOUT rail reference can be taken from any of the output terminals to give the range of outputs as described in the Output Voltage Configurations table below.[/quote]
JDB.
[I've used similar modules in non-audio designs. They're very simple to work with, but quiet they're not]

 

[mikep]

[quote author="jdbakker"]
[I've used similar modules in non-audio designs. They're very simple to work with, but quiet they're not][/quote]

ditto and watch for the magnetic field that comes out of these things! there is likely to be highly asymetrical leakage, ie one side you do not want facing the input transformer, or some other sensitive circuit element. just clip the ground lead to the tip of a scope probe in a nice big loop. sniff around with that. important to do BEFORE you do a pcb layout. not usually on the datasheet.

mike p