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How to Modify SMPS Output Voltage

I’ve got a number of iFi iPower and iPowerX power supplies with factory set voltages of 5V, 12, and 15V. I’m tying to power two devices that require 3.6V and 7.6V. Currently I am using some cheap store bought voltage regulators to take the iFi 12V power supplies down to the desired voltages. I got to thinking that if I could modify the iFi output voltages to the desired voltages, then I wouldn’t need the cheap voltage regulators - fewer lower quality devices in the power chain should improve sound quality. Does anyone know how to do this? I contacted iFi and they said their devices aren’t adjustable nor will they sell me custom voltage units. On some power supplies, it’s as easy as opening the device and adjusting a pot. In other cases, you can switch out a resistor to modify the voltage. I’m okay with voiding the warranty. Does anyone know if this can be done and if so, how to do it? Thank you.

128x128mkgus
mkgus's avatar
mkgus OP
324 posts
 

I’m trying to power a Sony PlayStation 1. The 7.6V is for the motor and the 3.6V is for the chips. I tried using 5V on the chips but the PS1 wouldn’t boot properly. 
 

Concerning using a simple resistive voltage divider, I have learned that there are a number of issues with it such as poor voltage regulation under load. However, if I have a decent power supply directly upstream of that, does that issue go away?

erik_squires
16,258 posts
 

Why are you getting so expensive / exotic with these supplies?  An off the shelf wall wart would be $30 or less.  You don't need super low noise supplies.

You are right.  A VR would be a much better solution than a R divider, but depends on current draws. 

mkgus's avatar
mkgus OP
324 posts
 

Erik - I have had excellent results upgrading the power supplies for my digital sources. Both my CD player and my DAC love these iFi low-noise, switch mode power supplies with active noise cancellation. Unlike the cheap wall warts, these were designed specifically for audio with attention paid to where it matters - low noise, low ripple, adequate capacitance, etc. My latest adventures have seen the version 2 iPowerX paired with a dedicated pure sine wave inverter powered by large SLA batteries. I have found power upgrades done right to provide massive payback and these iFi power supplies punch way above their weight class, doubly so when fed low noise pure sine wave 120V AC isolated from all the other components and the grid.

erik_squires
16,258 posts
 

I guess my big question was why a PS1 needed to be upgraded. :-)

As a hobbyist though you may have a lot more fun/success if you built your own linear power supplies.  A good pi filter and regulators can do marvels for noise.

mkgus's avatar
mkgus OP
324 posts
 

That’s a good question. I definitely enjoy DIY and tweaking things. I am somewhat on the fence about upgrading the PS1 power supply as a long term solution. Right now I am comparing the stock power supply vs. my DIY SMPS dual power supply solution. While I can clearly hear areas of improvement with my solution, I think the stock power supply might be more “musical.” I am wondering if the “magic” of the PS1 sound is partly caused by the stock power supply. The PS1 doesn’t measure that well yet many people will say it sounds great. Perhaps it’s shortcomings just so happen to be psychologically pleasing and I should leave it be. 

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