Smart people of DIYSB. Can we learn something about PSUs from this ?

[scuzzphut]

http://www.arcfn.com/2012/05/apple-iphone-charger-teardown-quality.html

Lowish component count. Super small footprint - could a variant of this design deliver 9Vdc noise-free ?

[anchovie]

It's got a super-small footprint because of the super-small (machine-placed) components. And there are way more components than my transformer/bridge rectifier/filter cap/voltage regulator box that took less than an hour to build and is noise-free!

[Perrow]

Bet the iPhone ps is switched (haven't read it). Switched ps's are never noise free AND low part count.

[R.G.]

Lowish component count. Super small footprint - could a variant of this design deliver 9Vdc noise-free ?

Noise-free?

Aye, there's the rub. 

[Cliff Schecht]

I believe at this point I've shared designs for how to get clean 18V from 9V, -9V from 9V and +/-15V from a single 9V input (all switching power supplies) in about the size of a nickel or dime. These are usually very small circuits but you have to be used to working with tiny components or you'll be cursing everything this (or that) side of the Mississippi.

Visual Sounds sells a better power supply that is specifically intended for pedals at a very fair price. TBH I'd have a hard time designing a supply that beats theirs, but they've already done it correctly so I don't feel the need to .


As far as this charger specifically, it might not be as easy as changing the resistor feedback ratio to get 9V instead of 5V out. This supply (and most SMPS's) have a compensation scheme that is used to ensure stability and if this isn't taken into account when changing the output supply voltage, instability can occur. An easy way to "guarantee" stability is to increase the capacitance in the feedback loop of the compensation circuit which has the effect of increasing the phase margin of the supply (a good thing) while slowing down the feedback loop transient response (a bad thing although probably won't hurt us).

This would work, but we might be better off finding a way to do a boost/buck power supply that takes in whatever voltage from 5V to 15V (or whatever we specify) and puts out a clean 9V regardless of the input voltage. This is easier to design and gets us around the problem of having to work with wall voltage, instead you plug in whatever wall wart you have laying around and start jamming.

[cthulhudarren]

The only thing that would make the 1 Spot better would be to have it adjustable so you can simulate battery sag.

[Earthscum]

The only thing that would make the 1 Spot better would be to have it adjustable so you can simulate battery sag.

(stupid phone deleted everything and posted... 'smart' phone my a**!)

IMO, that is specific enough to each circuit that you may as well just incorporate it into the design.

However, if Visual Sound were to make, say... a "Sag Jumper" accessory that you could just plug inline, that would be pretty awesome. A trick with it could be to split out to 2 different fuzzes right after the sag jumper, and the more it sags the more the 2 fuzzes will interact (oscillations and feedback, you know... noisy stuff!). If one were to exist, of course... there is always Dano's De-Volt until then: http://www.beavisaudio.com/products/devolt/

This could be made small enough (with the right trimmer pot) to almost fit in a jack. Little screw hole, and it's set and forget.