Discussion Will it smoke? 2x RPS-200, 1= picoPSU 1= GPU

jabcoebi

Chassis Packer
Original poster
Feb 6, 2019
15
22
www.reddit.com
Planning on using two MW RPS-200-12-C for a water cooling build, not the most compact at about 9~10L with 280 radiator support. The power supplies will sit under the radiator fans and be cooled that way.

Layout:
1x RPS-200 +12V -> picoPSU -> board + CPU
2x ground -12V -> picoPSU + GPU
1x RPS-200 +12V -> GPU

Is it a good idea to have the ground linked together or is better to keep them separate? And will the motherboard supply the GPU with power through the PCI-e socket?
My concern is for any conflicts between the two 12V supplies, technically a two rail PSU but with separate ground.

Is this achievable or I should just look for a more powerful 12V supply?
 

GuilleAcoustic

Chief Procrastination Officer
SFFn Staff
LOSIAS
Jun 29, 2015
2,967
4,390
guilleacoustic.wordpress.com
What GPU are you using ? Are you using a riser ? A powered riser ? If you need a PCIe power connector for your GPU there are solutions like the HDPlex DC-DC, instead of using multiple PSU (unless you already own them).
 

jabcoebi

Chassis Packer
Original poster
Feb 6, 2019
15
22
www.reddit.com
What GPU are you using ? Are you using a riser ? A powered riser ? If you need a PCIe power connector for your GPU there are solutions like the HDPlex DC-DC, instead of using multiple PSU (unless you already own them).

I'm using an undervolted 5700 (non XT) for the GPU, R5 3600 for CPU, no overclock and nothing high power, last time I checked the whole system was drawing 260W under stress test.

Thinking of not using a riser and going with the M1 layout style with some modifications and main reason for going with watercooling is low noise.

HDPlex is difficult to get in the UK.

Currently, the loudest part in my system is the PSU and would like to switch to a semi-passive solution where the PSU is cooled by the radiator fans, two 140mm fans in total for the whole system.
 

jabcoebi

Chassis Packer
Original poster
Feb 6, 2019
15
22
www.reddit.com
Just get the RPS-400-12-C?

Thanks for the sanity check! Upon further research I found the RPS-500-12-C which costs less than 2xRPS-200 and does not take twice the volume, even shorter than an FlexATX PSU. Rated at 320W with convection cooling it should have no issues with a 140mm fan spinning at 500RPM blowing air over it.
 

jabcoebi

Chassis Packer
Original poster
Feb 6, 2019
15
22
www.reddit.com
There are fully passive PSU, from Seasonic or Silverstone to name only 2 ;). HDPlex stuff are sent from US or Germany if you buy directly from them.

Yeah, there are many options like the Nightjar SFX-L from SilverStone, but it will take too much space and it will be wasted since this is not truly a fanless build. An RPS-500 + PicoPSU solution will take less space and I will not have to deal with all the cables. I prefer soldering a few wires here and there over using modular connectors, and not having to deal with that 24pin is a big plus for me.

I know that an off the shelf solution is better in every way, and less of a headache for me, but where's the fun in that. ?
 
  • Like
Reactions: Arboreal

GuilleAcoustic

Chief Procrastination Officer
SFFn Staff
LOSIAS
Jun 29, 2015
2,967
4,390
guilleacoustic.wordpress.com
  • Like
Reactions: Arboreal

smitty2k1

King of Cable Management
Dec 3, 2016
967
492
Thanks for the sanity check! Upon further research I found the RPS-500-12-C which costs less than 2xRPS-200 and does not take twice the volume, even shorter than an FlexATX PSU. Rated at 320W with convection cooling it should have no issues with a 140mm fan spinning at 500RPM blowing air over it.
Great! Make sure to post pictures! This going in a custom case?
 

jabcoebi

Chassis Packer
Original poster
Feb 6, 2019
15
22
www.reddit.com
Great! Make sure to post pictures! This going in a custom case?

Yes, custom case, not 100% decided on the layout, but a custom PSU will be necessary.

Vertical builds like the H1 have become popular lately, but I have already did a 280CLC 12L tower and other vertical builds.

With a custom PSU like this I have the option between a 10L H1 layout or a 6L A4 layout with better cooling. I’m leaning more towards the 6L build since I already had cases from 50L down to 8L, but never built something so small.

My idea is to have sandwich style layout but with the CPU and GPU fans being exposed and not sit under a grill to prevent any unnecessary noise.

concept case

It will definitely be a challenge.
 

smitty2k1

King of Cable Management
Dec 3, 2016
967
492
Yes, custom case, not 100% decided on the layout, but a custom PSU will be necessary.

Vertical builds like the H1 have become popular lately, but I have already did a 280CLC 12L tower and other vertical builds.

With a custom PSU like this I have the option between a 10L H1 layout or a 6L A4 layout with better cooling. I’m leaning more towards the 6L build since I already had cases from 50L down to 8L, but never built something so small.

My idea is to have sandwich style layout but with the CPU and GPU fans being exposed and not sit under a grill to prevent any unnecessary noise.

concept case

It will definitely be a challenge.
Great layout concept! I'd think a pair of 92mm x 15mm fans on top would be plenty. No need for anything thicker or additional fans
 

Valantar

Shrink Ray Wielder
Jan 20, 2018
2,201
2,225
Remember that the RPS-500-12 has a relatively high ripple spec (IIRC higher than what the ATX spec allows for), so while it will no doubt work, you can't expect your current undervolt to be stable.
 

smitty2k1

King of Cable Management
Dec 3, 2016
967
492
Remember that the RPS-500-12 has a relatively high ripple spec (IIRC higher than what the ATX spec allows for), so while it will no doubt work, you can't expect your current undervolt to be stable.
RPS 400 has better ripple IIRC
 

richi-123

Cable Smoosher
Jul 29, 2018
9
3
negative (black) wires have to be connected together for "interference", ground wires (green with yellow) go over metal parts of cabinet or psu

so you can use a low power picopsu, it does not need so much because the sources give maximum 50W in the 24 atx pins

gpu and cpu have their own 12v Molex that in this situation would come from the RPS-500 source

these two only need to have the negative cable in common, just in case not one because the current that passes through 12v and the negative is the same and if you have several 12v cables and a single negative that would have to withstand the current of several 12v

translated from google ??
 

jabcoebi

Chassis Packer
Original poster
Feb 6, 2019
15
22
www.reddit.com
Remember that the RPS-500-12 has a relatively high ripple spec (IIRC higher than what the ATX spec allows for), so while it will no doubt work, you can't expect your current undervolt to be stable.

Wow, totally forgot about output stability, thanks!
According to the datasheet:
RPS-500-12 = 200mV (peak to peak)
RPS-400-12 = 120mV (peak to peak)
RPS-200-12 = 100mV (peak to peak)

Meanwhile, something like the SilverStone Nightjar NJ450-SXL gets 26mV ripple at 12V 90% load and 45°C ambient temp, according to anandtech.com.
Going from ~20/30mV ripple to +100mV will definitely affect system stability.
Quite a difference, this changes things. Many thanks Valantar!
 

Valantar

Shrink Ray Wielder
Jan 20, 2018
2,201
2,225
Wow, totally forgot about output stability, thanks!
According to the datasheet:
RPS-500-12 = 200mV (peak to peak)
RPS-400-12 = 120mV (peak to peak)
RPS-200-12 = 100mV (peak to peak)

Meanwhile, something like the SilverStone Nightjar NJ450-SXL gets 26mV ripple at 12V 90% load and 45°C ambient temp, according to anandtech.com.
Going from ~20/30mV ripple to +100mV will definitely affect system stability.
Quite a difference, this changes things. Many thanks Valantar!
Even the technically put of ATX spec 500 is likely to be entirely stable at stock settings (at least for motherboards and GPUs with decent filtering in their VRMs, but any undervolt or overclock will inevitably be less stable with that kind of ripple. So yeah, it's something to look out for for sure. But also, remember that specs and actual performance don't necessarily match - at least for the lower power MW units their actual ripple is a good deal below the spec. MW publishes detailed test reports for their units on their site. Of course one should expect some variance, but they would have a serious QC issue if there were 2-3x ripple variance between units of the same model, so for the lower power units I tend to read the spec as a worst case scenario type of thing. The 400 still has a good deal more ripple than a top-end PC power supply, but whether it matters at all is another thing entirely.
EPP-500-12 report - 187mVp-p (spec 200)
EPP-400-12 report - 65mVp-p (spec 120)
EPP-300-12 report - 28mVp-p (spec 120)
 
  • Like
Reactions: smitty2k1

jabcoebi

Chassis Packer
Original poster
Feb 6, 2019
15
22
www.reddit.com
Even the technically put of ATX spec 500 is likely to be entirely stable at stock settings (at least for motherboards and GPUs with decent filtering in their VRMs, but any undervolt or overclock will inevitably be less stable with that kind of ripple. So yeah, it's something to look out for for sure. But also, remember that specs and actual performance don't necessarily match - at least for the lower power MW units their actual ripple is a good deal below the spec. MW publishes detailed test reports for their units on their site. Of course one should expect some variance, but they would have a serious QC issue if there were 2-3x ripple variance between units of the same model, so for the lower power units I tend to read the spec as a worst case scenario type of thing. The 400 still has a good deal more ripple than a top-end PC power supply, but whether it matters at all is another thing entirely.
EPP-500-12 report - 187mVp-p (spec 200)
EPP-400-12 report - 65mVp-p (spec 120)
EPP-300-12 report - 28mVp-p (spec 120)

Even the technically put of ATX spec 500 is likely to be entirely stable at stock settings (at least for motherboards and GPUs with decent filtering in their VRMs, but any undervolt or overclock will inevitably be less stable with that kind of ripple. So yeah, it's something to look out for for sure. But also, remember that specs and actual performance don't necessarily match - at least for the lower power MW units their actual ripple is a good deal below the spec. MW publishes detailed test reports for their units on their site. Of course one should expect some variance, but they would have a serious QC issue if there were 2-3x ripple variance between units of the same model, so for the lower power units I tend to read the spec as a worst case scenario type of thing. The 400 still has a good deal more ripple than a top-end PC power supply, but whether it matters at all is another thing entirely.
EPP-500-12 report - 187mVp-p (spec 200)
EPP-400-12 report - 65mVp-p (spec 120)
EPP-300-12 report - 28mVp-p (spec 120)

Thanks for the info! Any idea if an DC-DC convertor like the picoPSU XT-160 will amplify the ripple further? I’m assuming the 12V will not be greatly affected, but not sure how the ICs on the picoPSU will crosstalk back with the MW. Currently have an -96mV undervolt on an RX5700 with SGX-450 and it’s stable, but the city power is also relatively clean. Back home at the country side I have an R9 Fury with an -87mV undervolt and it’s not 100% stable. The power quality is very poor and fluctuates like crazy, I can also hear clicks and pops through some of my speaker amplifiers. Maybe a capacitor bank can help with filtering but it won’t fix the voltage fluctuations.
 

Thehack

Spatial Philosopher
Creator
Mar 6, 2016
2,800
3,650
J-hackcompany.com
Thanks for the info! Any idea if an DC-DC convertor like the picoPSU XT-160 will amplify the ripple further? I’m assuming the 12V will not be greatly affected, but not sure how the ICs on the picoPSU will crosstalk back with the MW. Currently have an -96mV undervolt on an RX5700 with SGX-450 and it’s stable, but the city power is also relatively clean. Back home at the country side I have an R9 Fury with an -87mV undervolt and it’s not 100% stable. The power quality is very poor and fluctuates like crazy, I can also hear clicks and pops through some of my speaker amplifiers. Maybe a capacitor bank can help with filtering but it won’t fix the voltage fluctuations.

You can use a pass-through design.

Search for the J-Hack M2426. It converts RPS-400/500 into regular ATX PSU. No need for a load switch.

If you have outlet power issue, you need a power conditioner. Many UPS also power conditions. But it may also just be just a function for Furys. They're known to have high transient power requirements.