GB for Simple Cap-Mx Regulated Low-Noise PSU

[xrk971]

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.

Thanks,
X

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:
https://www.digikey.com/product-detail/en/7447017/732-1418-ND/1638823/?itemSeq=289294179

https://katalog.we-online.de/pbs/datasheet/7447017.pdf

Version 2 of the board:

 

[Vunce]

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]

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]

DIYJohnDoe - 2 boards - USA

I'm in for two.

 

[xrk971]

Thanks for starting it off DrPro!

Ok here is the beginning of the list.

DrPro - 2 boards - USA

 

[Vunce]

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

 

[goldkenn]

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

 

[xrk971]

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

 

[Yatsushiro]

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

 

[Mindfunk]

Mindfunk - 4 boards - Germany

 

[Mindfunk]

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

 

[xrk971]

Thanks for the continued interest folks. It has just come to my attention that a 3A 5v 4.4uV LDO VR just came out from TI:

http://www.ti.com/product/TPS7A84A

Interesting for RPi

 

[drpro]

X that would be really nice. I am interested in RPI power. Having 3amps would be great.

 

[xrk971]

The 3A 5v regulator is a separate project - but let me see how we can make one. 3A at 5v is 15w upstream.

 

[Roundtoit]

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

 

[xrk971]

Thanks to member Twocents for being a beta tester on v1 - nice build with an eBay TPS7A4xx LDO regulator.

 

[maartn]

DrPro - 2 boards - USA
Vunce - 2 boards - USA
goldkenn - 4 boards - Hong Kong
Yatsushiro - 2 boards - France
Mindfunk - 4 boards - Germany
maartn - 3 boards - Netherlands

 

[Lo_Tse]

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.

Thanks,
X

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

Hi there

Would you mind telling me what is the value of the inductor in the CLC section? I am checking to see what components I already have and what I need to purchase for this PSU before deciding whether to join this GB. Thanks!

Regards,

 

[xrk971]

It’s very flexible what size inductor you can use. The characteristic cutoff frequency of an LC filter is 1/(2 pi sqrt(LC)). If you use a 1000uF cap and say 10uH inductor, you have 1.6kHz filter cutoff - well below the switch frequency of the SMPS by many octaves so the filtering should be steep. You could even use a much smaller cap like 100uF and it would be fine as that is 16kHz and switchers are 200kHz to 400kHz.

Make sure you have a resistor in parallel with the inductor to prevent oscillation. Something like 33R to 47R or 51R works.

The inductor specified in the schematic is a Wurth 7447017 22uH. Or 1072Hz cutoff frequency.

7447017 Wurth Electronics Inc. | Inductors, Coils, Chokes | DigiKey

 

[Lo_Tse]

Thank you for the fast response!!