In order to feed a pre-amplifier, I need +/-12 and +/-24 V power supply. The current requirements are very low (< 50 mA).

Is it possible to use two single power supplies (e.g. TDK-Lambda LS-75-12) and 2 power supplies[URL='https://www.conrad.be/p/tdk-lambda-ls-75-12-acdc-inbouwnetvoeding-132-vdc-6-a-75-w-511823']TDK-Lambda LS-75-24 to create the require power supplies?[/URL]

How should we connect the +/- V terminals? and how shall we make the ground (zero?).

For information the power supplies have +V, -V and GND terminals.

 

Here is how you can create a dual power supply from two 9V batteries.

You can use the same principle with bench power supplies as long as the outputs are "floating".

 

Another option would be to use switching regulators to generate the required voltages from a 12V supply.

 

Check out the various power supplies in the "power" section at the "schematicsforfree"website. Lots of downloadable circuits there. No helpful comments, but lots of circuits.

 

How should we connect the +/- V terminals? and how shall we make the ground (zero?).
For information the power supplies have +V, -V and GND terminals.

The ground connection is for the AC input if using a three conductor cable.
Connect V- of power supply #1 to V+ of power supply #2, this will be the common connection to "ground" on the amplifier circuit. V+ on supply #1 is your +12 vdc, V- on #2 is your -12vdc. Same connections for the 24 volt supplies. Definite overkill for a preamp that only needs 50ma though.
SG

 

Thank you fellows. One additional question. Is it possible to connect the grounds of the four power supplies together? something like on the schematics here? I have plenty of 5 pin amphenol connectors (and yes... more current cos I have 9 pre-amps and they have to work several .. tens of years ).

 

The above wiring is correct. The ground connection shown is the ground on the preamps.
SG

 

The circuit shown is indeed correct, but I need to add that in addition, the impedance of the ground connections from the power supplies needs to be quite low. Any resistance in the common ground line will result in some amount of interaction between the different loads connected, and that may cause problems that will be a challenge to solve.