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DIY Eurorack Power Supply - New and Improved
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author DIY Eurorack Power Supply - New and Improved
Metatronic Mods

It's been a year since I started selling my original power supply design PCB's, and I've been very pleased both with the test results and the customer feedback I've received for it. But there were a few adjustments I wanted to make (mostly convenience features) and I'm now ready to announce Version 3 of the design.

You can read the full specs on my site linked below, but the major improvements over the last version are:
    Increased output power +12/-12/+5V @ 3/1.5/1A
    Double thickness copper clad PCB
    Included mounting for toroidal transformer
    Total of 8 outputs which accept pin headers and tab connectors for doepfer style bus boards
    Even lower ripple & noise on the outputs (2.53mV at full load)


If you're interested you can find full specs, pictures, and purchase PCB's here: http://www.metatronicmods.com/store/p9/Ver._3_Analog_Power_Supply_for_ Eurorack_Modular_Systems__12%2F-12%2F_5v_%40_3A%2F1.5A%2F0.5A_%28Linea r_3-Pole_PSU%29.html
AonFLuX
Could not contain myself - and bought my first euro-rack stuff. This PSU PCB...


So it begins... sad banana
Metatronic Mods
AonFLuX wrote:
Could not contain myself - and bought my first euro-rack stuff. This PSU PCB...


So it begins... sad banana


applause
BugBrand
How hot do the heatsinks get if you're drawing full load? They look suspiciously small for 3A/1.5A, but then I never looked too much at LDO regulators.
Metatronic Mods
BugBrand wrote:
How hot do the heatsinks get if you're drawing full load? They look suspiciously small for 3A/1.5A, but then I never looked too much at LDO regulators.


That will depend heavily on ambient temperature and convection in your case. On my test bench exposed to ~22C ambient temperature they sit at around 47C under full load.

A lot of the design was meant to minimize inefficiencies of the regulators by ensuring that the electronics ahead of the regulators provide just enough voltage to overcome the regulator dropout at full load and worst case external conditions of 90% nominal mains voltage. This is why the design implements such a large reservoir capacitor bank, discrete 5400 diodes and NTC thermistors.
Metatronic Mods
Also to be clear, it's not that LDO regulators are more efficient per say, they'll put out the same amount of heat as a non-LDO regulator operated in the same conditions.

What they do allow for is a lower minimum input voltage which, done right, allows for a smaller voltage drop across the regulator input and output, and thus less heat dissipated.
AonFLuX
So, looking to score all the parts for the board i just purchased (thanks!).
But the +12V reg seems to be hard to get (factory special order on Mouser).
As an alternative I found this: http://www.mouser.com/ds/2/149/KA378R12CTU-1010659.pdf

It has instead 4 pins with the 4th being an on/off for the output, that shuts the output if voltage on that pin drops below about 2V. Could I simply jumper this pin with the input-pin (which should be above 2V any time you have the PSU running)?
Some additional small pin-bending will probably also be needed to fit it in the PCB.
Graham Hinton
Metatronic Mods wrote:
A lot of the design was meant to minimize inefficiencies of the regulators by ensuring that the electronics ahead of the regulators provide just enough voltage to overcome the regulator dropout at full load and worst case external conditions of 90% nominal mains voltage.


Worst case conditions are nominal mains +10%, not -10%. All mains designs should be able to cope with the variations that will be found in real use which is +/-10%. LDO regulators are intended for regulating a DC voltage that has less variance, e.g. one that is already regulated to some extent.

Quote:
What they do allow for is a lower minimum input voltage which, done right, allows for a smaller voltage drop across the regulator input and output, and thus less heat dissipated.


They might save 1 or 2W in a 100W PSU. Do the maths.
Metatronic Mods
AonFLuX wrote:
So, looking to score all the parts for the board i just purchased (thanks!).
But the +12V reg seems to be hard to get (factory special order on Mouser).
As an alternative I found this: http://www.mouser.com/ds/2/149/KA378R12CTU-1010659.pdf

It has instead 4 pins with the 4th being an on/off for the output, that shuts the output if voltage on that pin drops below about 2V. Could I simply jumper this pin with the input-pin (which should be above 2V any time you have the PSU running)?
Some additional small pin-bending will probably also be needed to fit it in the PCB.


I can't recommend that course of action since I haven't tested it personally. My recommendation would be to check another vendor, though as I say that I see Digikey is currently out as well. Perhaps someone else though. Or if you want to PM me I can arrange to have one sent to you.
Metatronic Mods
Graham Hinton wrote:


Worst case conditions are nominal mains +10%, not -10%. All mains designs should be able to cope with the variations that will be found in real use which is +/-10%. LDO regulators are intended for regulating a DC voltage that has less variance, e.g. one that is already regulated to some extent.


Yeah, you're right. I meant worst case on the performance side, as in before loss of regulation. Of course worst case, supply side, would be +10%. I have given her a hot supper without any problems. But I would definitely be concerned if it were a tight enclosure, full load and 110% mains input. I've said before, a little convection cooling goes a long way, and conversely this really isn't the right design for compact skiff cases.

Quote:


They might save 1 or 2W in a 100W PSU. Do the maths.


I have, and you're more or less right. As I recall the savings weren't quite so modest, but the biggest provision they allowed for were the inrush limiting thermistors without needing to increase the transformer output voltage to maintain regulation at load. I explained it better in an earlier build doc.
AonFLuX
Metatronic Mods wrote:

I can't recommend that course of action since I haven't tested it personally. My recommendation would be to check another vendor, though as I say that I see Digikey is currently out as well. Perhaps someone else though. Or if you want to PM me I can arrange to have one sent to you.


Thanks for the offer and considerations - and there is always the Ebay/China-option, of course. But it just seems like the 3-pin version of +12V/3A regulators are hard to get. Maybe they are being phased out?
Metatronic Mods
AonFLuX wrote:


Thanks for the offer and considerations - and there is always the Ebay/China-option, of course. But it just seems like the 3-pin version of +12V/3A regulators are hard to get. Maybe they are being phased out?


I don't know. I've seen large volumes go in and out of Mouser and Digikey, seems to me someone found a popular use for them.
jmsiener
Bringing back an old thread. Shout outs to this PSU - has had all 16u of my case humming perfectly with no issues. About the only sad thing is that the spring tanks in the case are prone to him from the transformer. Otherwise all of my modules are noise free, except for the ones that are supposed to be. razz
Jarno
Move the reverb tanks somewhere else? And also, try different (better) cables to and from the reverb tanks.
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