24V AC power supply for MAX.


2006-11-18 11:36 pm
I'm considering building a Millet Hybrid MAX headphone amplifier, but since i am allergic to wall warts, i need another solution. The recommended in voltage to the MAX is 24V AC. I'm in Norway, which means 230V mains, and if i understand correctly i can get my AC from a simple toroidal transformer. I have one that is 230V in and 2x24V out. 10VA on each secondary. I gather i can use this. Couple the two secondary windings in series and get 20VA. Does this seem right?

The case i have for the PSU has a chassis contact with a built in fuse holder and on/off switch. (I also have another case, but without the chassis contact, that i will put the MAX into) So if my assumptions are correct I'll just need a way to get the 24V from the secondary windings to the MAX. Here I'm thinking some kind of Neutrik chassis contacts and a piece of cable with corresponding Neutrik plugs to put between the two cases.

I would also like to have an indicator of some sort in the PSU case that tells me when it is active. An LED for example. What is the easiest way to attach a LED when only 230V and 24V AC is available? Some sort of rectifier on the 24V side and a resistor in series with the LED?

Any help is greatly appreciated.


2007-03-19 8:41 pm
No, connect them in parallel. Make sure the phase is correct. An easy way to check is with a voltmeter. Connect one end from each coil together and measure between the two free ends. If the phase is correct, there should be little or no voltage. Switch one end of a coil if there is about double the voltage between the ends.

For the LED, use a resistor and rectifier diode.