Hi everyone,
I’m currently working on a compact audio device and I’m looking to design a dual-rail ±17V power supply. The current demand is fairly low (~500 mA), and the whole build needs to remain low profile and as noise-free as possible for audio use.
The idea is to use a single-rail SMPS as the primary power source, then derive both positive and negative rails from it, whether through DC-DC converters or another topology is still open at this point.
I’ve been following Mark’s contributions on power supply filtering for some time, especially the AmyAlice designs, and I plan to integrate a similar filtering stage at the output. I’ve gone through a number of previous threads and feel fairly confident about that part, but I’d love to hear your ideas or experience when it comes to:
Would be great to hear what’s worked well for you, or any pitfalls to avoid.
Thanks in advance for any input you’re willing to share!
Best,
Ahmed
I’m currently working on a compact audio device and I’m looking to design a dual-rail ±17V power supply. The current demand is fairly low (~500 mA), and the whole build needs to remain low profile and as noise-free as possible for audio use.
The idea is to use a single-rail SMPS as the primary power source, then derive both positive and negative rails from it, whether through DC-DC converters or another topology is still open at this point.
I’ve been following Mark’s contributions on power supply filtering for some time, especially the AmyAlice designs, and I plan to integrate a similar filtering stage at the output. I’ve gone through a number of previous threads and feel fairly confident about that part, but I’d love to hear your ideas or experience when it comes to:
- Choosing an appropriate SMPS module (PCB or chassis mount) for this kind of setup
- Approaches to generating dual rails (±17V) from a single supply input
- Layout or integration tips when combining regulation and filtering for audio-sensitive applications
Would be great to hear what’s worked well for you, or any pitfalls to avoid.
Thanks in advance for any input you’re willing to share!
Best,
Ahmed
If you're going to use an SMPS anyway, why not just use a dual-rail SMPS?
The two main approaches for generating dual rails from a single rail are going to be either a DC/DC converter, or a rail splitter.
Nearly all SMPS manufacturers have dual rail DC-DC converters. For example, I am using a small module from Traco Power for prototyping. They're very convenient when you don't want to mess with mains wiring.
This model (Traco TEN-8-1223) does not meet your particular requirements, but they have many others...
The two main approaches for generating dual rails from a single rail are going to be either a DC/DC converter, or a rail splitter.
Nearly all SMPS manufacturers have dual rail DC-DC converters. For example, I am using a small module from Traco Power for prototyping. They're very convenient when you don't want to mess with mains wiring.
This model (Traco TEN-8-1223) does not meet your particular requirements, but they have many others...
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+-17V is a bit of unusual output voltage where it is harder to find ready-to-use modules as it is a bit outside the typical +-10% adjustment range (if adjustable, that is) for both 15V and 24V models.
If you afford it I'd certainly suggest using two (medical) isolated 15V DC/DC modules like TRACO THM10 15V single output which have a +20% adjustment range (18V). Give each of them a 17V/500mA post-regulator with an LT3045 and it will be as good as it gets.
That said, it is not too hard to design a SEPIC-CUK dual rail SMPS with 5V or 12V input: https://www.analog.com/en/resources/app-notes/an-1106.html
I recently did a design where I needed +-7.5V/200mA and +-17V/50mA from a 5V input voltage in an extremely compact form factor. I went for a stacked SEPIC-CUK converter based on the LT1935 and it works really well (reality fully matching the simulation). Of course the layout is absolutely critical with a 1.2Mhz switching frequency, I used 6 layers to realize a ultra-compact "zero loop area" layout...
If you afford it I'd certainly suggest using two (medical) isolated 15V DC/DC modules like TRACO THM10 15V single output which have a +20% adjustment range (18V). Give each of them a 17V/500mA post-regulator with an LT3045 and it will be as good as it gets.
That said, it is not too hard to design a SEPIC-CUK dual rail SMPS with 5V or 12V input: https://www.analog.com/en/resources/app-notes/an-1106.html
I recently did a design where I needed +-7.5V/200mA and +-17V/50mA from a 5V input voltage in an extremely compact form factor. I went for a stacked SEPIC-CUK converter based on the LT1935 and it works really well (reality fully matching the simulation). Of course the layout is absolutely critical with a 1.2Mhz switching frequency, I used 6 layers to realize a ultra-compact "zero loop area" layout...
This is what I did for my headphones amp.
It encompasses an input filter and a 317-based regulator à la Mark's Tuba, duly denoised as per Elvee's Denoiser, https://www.diyaudio.com/community/...o-retrofit-upgrade-any-317-based-vreg.331491/ and finally split in two creating a virtual ground. The result is: the amp is absolutely silent, the two rails are perfectly balanced (even in case of an unbalanced charge). Credits in https://www.goldpt.com/virtual_ground_circuit.html
Nothing new from my part, I just "glued" (or even copy-pasted) other's ideas
Guido
It encompasses an input filter and a 317-based regulator à la Mark's Tuba, duly denoised as per Elvee's Denoiser, https://www.diyaudio.com/community/...o-retrofit-upgrade-any-317-based-vreg.331491/ and finally split in two creating a virtual ground. The result is: the amp is absolutely silent, the two rails are perfectly balanced (even in case of an unbalanced charge). Credits in https://www.goldpt.com/virtual_ground_circuit.html
Nothing new from my part, I just "glued" (or even copy-pasted) other's ideas
Guido
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Thanks a lot everyone for your valuable insights, it's really helpful to hear different real-world approaches.
I really like the idea of using isolated DC-DC modules trimmed with LDOs, it feels like a clean and quiet solution, and aligns well with the direction I'm exploring (stip on budget but will look at different modules). That said, I’m curious: why would one choose an Elvee denoiser with a virtual ground instead of something like the AmyAlice filter (or A²CMx) for audio applications? Is it mostly a space/power tradeoff, or are there sonic advantages in that topology?
Also @GuidoR just to clarify, are you confident that asymmetrical load won’t be an issue in your setup? From what I understand, a headphone amp is typically quite balanced in current draw, but in my case the load may lean more to one rail, so I’m cautious.
Thanks again to everyone who’s shared so far, I really appreciate the thoughtful input 🙂
I really like the idea of using isolated DC-DC modules trimmed with LDOs, it feels like a clean and quiet solution, and aligns well with the direction I'm exploring (stip on budget but will look at different modules). That said, I’m curious: why would one choose an Elvee denoiser with a virtual ground instead of something like the AmyAlice filter (or A²CMx) for audio applications? Is it mostly a space/power tradeoff, or are there sonic advantages in that topology?
Also @GuidoR just to clarify, are you confident that asymmetrical load won’t be an issue in your setup? From what I understand, a headphone amp is typically quite balanced in current draw, but in my case the load may lean more to one rail, so I’m cautious.
Thanks again to everyone who’s shared so far, I really appreciate the thoughtful input 🙂
Hi Ahmed, indeed current draw is typically balanced for my headphones amp, but the circuit appear tolerant to the imbalances. You can try the splitter part alone on a breadboard, it's a handful of inexpensive and common components.
Re. Denoiser, I started from Mark's TUBA (including the input filter - not as refined as the AmyAlice but effettive anyhow), adding Elvee's "trick" to the regulator part, with the aim for a reduced noise. At this point I added the 317-based splitter.
I can't report any actual measurement, nor express any opinion on sound, I only can say that the amp is dead silent, and this is enough for me. 😉
But there are many ways to skin a cat, that's DIY😁
Re. Denoiser, I started from Mark's TUBA (including the input filter - not as refined as the AmyAlice but effettive anyhow), adding Elvee's "trick" to the regulator part, with the aim for a reduced noise. At this point I added the 317-based splitter.
I can't report any actual measurement, nor express any opinion on sound, I only can say that the amp is dead silent, and this is enough for me. 😉
But there are many ways to skin a cat, that's DIY😁