48 volts from a wall wart?

[Bear]

I'm bad with power supply stuff, but I think I've seen that this is a possibility. I'm interested in tossing together the Hamptone JFET Stompbox kit with some available iron in a new box as a single channel mic preamp. I wouldn't mind just using it for dynamics and DI, but I wanted to ask about the feasability of grabbing a 48 volts without adding a more substantial transformer. Some kind of voltage doubler?

Bear

 

[kato]

Did you see mnats reinterpretation of the hamptone jfet pre? He gets 24v for phantom which is sufficient for some condensers.

http://mnats.net/hamptone_jfp.html

 

[gemini86]

a lot of the newer mics use zeners to knock the 48v down to 12v, which run the circuit, then use an internal booster converter to pump 12v up to whatever voltage they want for the capsule. 48v isn't really needed anymore for most mics. Give 24v a try and see how it works for your mics, then worry about that problem, once it's actually a problem.

 

[JohnRoberts]

With an AC lump, you can use a cap doubler/tripler to make 48V. With a DC lump you can use a DC-DC convertor to make anything from anything.

Think of it as an opportunity to expand your design horizons.

JR

 

[PRR]

It's trivial if you find 24VAC warts. They are used in alarm and cable systems.

www.jameco.com
AC-to-AC ADAPTER, 24V @ 500mA, BLACK, STRAIGHT 2.1mm FEMALE PLUG
Part no. 87581
$8.95 each

 

[kato]

Also somewhere on the Rane website once was a schematic for getting bipolar power and 48v from a wall-wart. I believe I saved it somewhere if it's no longer available. Also I think rlaurey posted something similar at one point.

 

[buildafriend]

How can I see a cap doubler or tripler? Is it a circuit or a single component?

 

[gemini86]

the upper portion of this schematic is a voltage doubler, note the caps in series from the transformer to the upper bridge rectifier.

http://www.jlmaudio.com/ACDCVer2sch.pdf

See also: http://en.wikipedia.org/wiki/Voltage_multiplier

 

[zapnspark]

MPJA.COM has a 48 VDC wall wart power supply:
MFG: AULT
P/N: SC102TA4803B01
Input: 100-240VAC 47-63Hz
Output: 48VDC @ 0.38A
Specifications/Features:
Wall mount switching supply. Non-polarized 2 blade input, 6ft. ZIP cord
with 10mm long X 5.5/2.5mm coaxial power plug Center +. ULus/canada listed.
L: 3" W: 2" T: 1-5/8" WT: .46
Stock No.:  18559 PS Price: $6.95

Cheers.

ZAPNSPARK

 

[gemini86]

take that .38A and cut it in half for +-24V. I don't know how much current the hamptone fet amps use...something you should probably find out before committing to a PSU.