[G.Michael]

I wanted a low-noise power supply to run my 4th gen iMod (the Red Wine Audio modification to the iPod).  The mod to the 4th gen iMod takes the output from the headphone jack, so the port in the bottom of the unit can be used to power the unit and charge the battery while the unit is playing. 

I'm running Rockbox software instead of iTunes, and Rockbox seems to suck up more current, hence the need for a good power source in addition to the battery, while the iMod is playing.

I went with an Acopian linear regulated power supply module, as you see in the photo.  These modules retail for $126, but can be found on eBay for a lot less.  (I paid about $25 for mine.)  The 5EB150 model number means 5 VDC output, 1.5 Amps max.







I got the chassis at Radio Shack.  Ouput connectors are the common 2.1 mm jacks.  Simple switch and an LED with series resistor.  IEC inlet has an EMI filter built-in; not necessary, but I had one on the shelf, so I used it.   

Since I used 2.1 mm output jacks, I needed to come up with the adaptors and cables to get the power to the iPod.  It took some internet searching, but here’s what I got:



[As I mentioned above, the Acopian modules can be found on eBay.  Since I built this 5 VDC supply I bought a few extras.  A couple of ‘em appear to be NOS.  So, if you want one and don’t want to go the eBay route, PM me.]

So, how does it sound?  I hear no added noise when I use the power supply + battery instead of battery only.  If anything, the sound is a little more dynamic.

[jtwrace]

This is great!  I've been looking at linear power supplies.  I'm wanting to get rid of my switching power supplies for my external HD's.  They have a dual output linear.  I've got to check the specs...

Are these linear supplies any good?  Anyone else have experience with them?

[G.Michael]

To test the Acopian power supply module, I put a high wattage 8 Ohm resistor across the output.  I'm not sure of the exact number, but I know there was very little voltage sag.  5 volts, 8 Ohm means 625 mA of current, which is considerable for one or two USB devices.  With the same load, I measured the AC... in theory my meter is accurate to within 1 mV, and I measured 0.000 VAC.  I don't quite assume that the ripple is that low, but I think it's pretty low.

[jtwrace]

To test the Acopian power supply module, I put a high wattage 8 Ohm resistor across the output.  I'm not sure of the exact number, but I know there was very little voltage sag.  5 volts, 8 Ohm means 625 mA of current, which is considerable for one or two USB devices.  With the same load, I measured the AC... in theory my meter is accurate to within 1 mV, and I measured 0.000 VAC.  I don't quite assume that the ripple is that low, but I think it's pretty low.

Good to hear.

[jtwrace]

Oh one more thing.  Is there any audible noise from the PS?  Power supply noise not line noise through the source. 

[G.Michael]

I've built two of these power supplies.  I can hear noise from one of them when I put my ear up to it.  But basically it's very quiet.  You'll notice from the first pic that I wired it so that I can easily replace the module--just in case it does get noisy.

The bottom of the module has four machine screw inserts built in... it takes four #4 machine screws to hold it in place.  The hardest part of building the supply was drilling the four holes in the bottom of the chassis such that they lined up with the screw holes.