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xrk971 22nd February 2019 09:41 PM

GB for Simple Cap-Mx Regulated Low-Noise PSU
4 Attachment(s)
Have you ever found yourself making a basic circuit that is so simple, that you say to yourself, "it's so simple I will just make it from scratch on veroboard..." It works so well and is so useful, it becomes an integral part of many of your future projects. Before you know it, you have hand-assembled on veroboard the same circuit a dozen times. Well that's what I have been doing whenever I needed a source of ultra quiet (battery-like) single-rail DC power in the range of 5v to about 32v and current under 1amp. I use this countless times for low noise headphone projects, DACs, etc. Well, I sort of got tired of making them from scratch and worked with JPS64 to put it on a simple 50mm x 75mm board the following: a CLC filter, an Easy-Peasy Juma cap multiplier, and a 78xx regulator, and throw in some smoothing caps, snubbers, output bypass caps, and LED power indicator, and input/output terminal blocks. I typically use a 12v 1000mA Class 2 transformer wall-wart ubiquitous with routers and switches that we accumulate over the years. That then powers a clean DC-DC step up converter to about 4v+ regulator dropout (circa 2v) above our needed voltage. So for example, if you need a clean 18v supply, add 5v or 23v as the DC-DC stepup output. Put that into this unit, and let its cap CLC filter, cap multiplier, and voltage regulator give you a clean source of 18v with ripple as low as 4uVrms (if you use a TO-220 formatted TPS7A4xxx LDO regulator). If you can live with 50uV noise,a simple 7818 regulator will work fine. I have used this on countless headphone amps and the noise floor measures flat like a battery. Absolutely no mains hum gets through.

Thanks to JPS64 for a great layout with all the customary via stitching and double planes of copper for low impedance current paths.

So here is the circuit:

This is what it looks like built up in prototype stage v1:

And here is the board will look like for the v2 (will be 1.6mm thick, 1oz copper, green mask, and ENIG finish):

Here is the top view of the parts placement. BOM for the board is relatively cheap if you are going with just a 78xx. You need an N-channel TO-220 MOSFET such as an IRF610 or the Fairchild equivalent. IRF510 etc works well too. A few caps and resistors, some connectors, and a basic inductor to keep the DC-DC noise even more isolated.

If interested in this little PSU board as a GB, please add your name, number of boards, and country to ship to below.

Like this:
DIYJohnDoe - 2 boards - USA

Pricing will be about $10 ea and tracked shipping in a padded bubble envelope mailer is the usual $5 in US, $10 for CAN, and $15 everywhere else. Maximum 8 boards per order for the above shipping prices.


Some supporting info, you can see in the photo below, a hand-made variant of this PSU (without a voltage regulator) powering my Aksa Lender preamp, the DC-DC step up is visible as well. Here I was running 48vdc output so a 78xx regulator could not have been used as they max out at 35vdc input:

Here is the FFT from the Aksa Lender showing the typical clean battery like noise floor:

Another example is the PSU that is built into the DCA Single ended Class A HPA (also without a VR):

Here is the typical FFT from the DCA:

Finally, another example is the similar PSU built into the Aksa-Lender preamp GB:

And typical FFT of the Aksa Lender putting out 20vpp into 7kohms:

So you can see how well this supply works in general and how I keep coming back to it. Just use a $4 to $7 DC-DC step up to get whatever voltage you need.

These types of DC-DC work well, for example:

DC DC 250w Boost Converter Step-up 10a Constant Current Power Supply LED Driver | eBay

400W 15A DC Step-up Constant Current Power Supply LED Driver Boost Converter | eBay

400W 15A DC Step-up Constant Current Power Supply LED Driver Boost Converter | eBay

DC-DC Step-up Boost Converter Constant Current Power Supply 10A 250W LED Driver 6472005271954 | eBay

Edit Feb 25, 2019: Member Twocents was a beta tester for v1 and he installed an eBay 5v TPS7A4xx LDO board on it - nice work!

And use a 12v 1000mA Class 2 Wall wart like this, for example:
Class 2 Power Supply Unit FL41A20U120V120A1000 Adapter 12V 1000mA Charger | eBay

Edit Mar. 14, 2019:

You can use the Wurth 774701 Choke:

Version 2 of the board:

Vunce 22nd February 2019 11:20 PM

Hi X,
This little psu pcb would be very useful to have for many projects. I was just contemplating how I want to feed my Korg B1 Buffer/preamp a super clean regulated 24vdc. Since I have the dc-dc step up and class 2 wallwart, this psu board seems like a great match.:)

xrk971 22nd February 2019 11:31 PM

Yes, preamps are the primary use for these power supplies. Although I can see that they would work well for high end DACs needing 9v of RPi’s needing a clean 5v source.

drpro 23rd February 2019 02:52 AM

DIYJohnDoe - 2 boards - USA

I'm in for two.

xrk971 23rd February 2019 03:14 AM

Thanks for starting it off DrPro!

Ok here is the beginning of the list.

DrPro - 2 boards - USA

Vunce 23rd February 2019 03:32 AM

DrPro - 2 boards - USA
Vunce - 2 boards - USA

goldkenn 24th February 2019 05:46 AM

DrPro - 2 boards - USA
Vunce - 2 boards - USA
goldkenn - 4 boards - Hong Kong

xrk971 24th February 2019 05:57 AM

Cool - we are getting a little more interest finally. Thanks DrPro, Vunce, and Goldkenn.

Yatsushiro 24th February 2019 08:58 AM

DrPro - 2 boards - USA
Vunce - 2 boards - USA
goldkenn - 4 boards - Hong Kong
Yatsushiro - 2 boards - France

Mindfunk 24th February 2019 11:37 AM

Mindfunk - 4 boards - Germany

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