[sdiy] Opionions on Switchmode PSUs for analog synths?

Ben Stuyts ben at stuyts.nl
Wed Oct 30 22:48:58 CET 2019


Hi Neil,

Depends if you can tolerate the noise. I’ve used quite a few products from Mean Well, and although their price if very good, their noise and EMC performance is terrible.

There is orders of magnitude in difference in noise between these kinds of DC/DC converters and a good low-drop-out analog regulator. I’m currently looking at a LT3088 LDO (3-pin, needs one ext resistor to set output voltage) at https://www.analog.com/en/products/lt3088.html#product-overview <https://www.analog.com/en/products/lt3088.html#product-overview>. It has 27 uV RMS noise. The Mean Well has 3 orders of magnitude more. So if you have the budget, go for some SMPS to generate pos and neg and followed with some analog regulators. Maybe even put a point-of-load regulator on each board.

BTW, do you have to use a wallwart? Regular transformers are plentiful.

On the other hand, there were similar awful DC/DC converters in Buchla 200e boats and nobody complained…

Ben


> On 30 Oct 2019, at 21:45, Neil Harper <metadata at gmx.com> wrote:
> 
> so i'm putting together a new diy modular system, it's been over a
> decade since i built my last ones. my knowledgebase is firmly in the
> horowitz & hill era, so my previous psu was an lm317/lm337 based affair
> that took a 16VAC wallwart to power.
> 
> that psu worked fine, but i'm noticing the 16VAC wallwarts are
> increasingly hard to find, almost impossible in europe. more of my gear
> is now coming with a switchmode dc wallwart and an internal switchmode
> power supply to generate internal bipolar (+/-12VDC) supplies.
> 
> i was always told that switchmode power supplies suck for audio, so
> taking a switchmode dc wallwart and then putting it into another
> switchmode powersupply seems like it would be a recipe for noise - but
> this seems to be what is inside almost every product now. the forgiving
> input voltage range (9 to 18VDC for example) is very appealing and so is
> the availability of dc supplies.
> 
> there's a lot of these encapsulated supplies, delivering +/-12VDC:
> 
> https://www.jameco.com/z/DKE10A-12-MEAN-WELL-Power-Supply-Encapsulated-DC-DC-2-Output-12-Volt-12-Volt-0-42A-0-42A-10W-5-PIN-DKE10A-12-MEAN-WELL_217092.html
> 
> anyone successfully using these things in synths? how are they comparing
> to old school rectified linear regulated power supplies? what's your
> favorite pizza toppings? are you doing anything special on the rails to
> filter for switching noise, etc?
> 
> 
> 
> 
> 
> --
> /// Neil Harper
> /// Every Wave is New Until it Breaks
> 
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