V3 Universal Power Supply Circuit Board

Maybe I am asking for too much here but could someone post an equation that could help calculate output voltages with variable values represented by the component identifier (for example: R1).

Output voltage ~ (1.4 * VAC) -1.2 (1.2 varies depending on the forward voltage drop of the diodes chosen and operating current, see the data sheets, but 1.2 will get you in the ballpark) Subtract a bit more if you go with the CRC option.

R1 (optional) etc. are your call. You probably want to keep the net of the paralleled resistors under 0.1R although there are bound to be some differences of opinion. If you don't want to go CRC, just jumper one or more positions.

R9, R18 (bleeder) again your call. Pick a value that will bleed off your caps in a reasonable amount of time without dissipating too much heat. Around 50-60V try 4.7K/4+ W.

R21, R28 LED current limiters. You pick to set your LEDs at desired brightness. R = (V-Vf)/I Where V is rail voltage, Vf is forward voltage drop of your LED and I is desired current. Typical values for Vf are blue=5V, green=2V, red=1.2V Probably close enough for calculating R without going into the datasheet. I find most blue LEDs are too bright at 5 mA, YMMV.

R11, R12, C17, C18 - Snubber, optional. The values on the board are general purpose, your needs may vary depending on your particular transformer, rectifiers and capacitors. You can feed your amp high frequency square waves at near max power and look for ringing on the rails as you adjust values. There are ways to calculate values, look for the snubberized thread.

There is a snubber on the rectifier board, also optional, as above.

Hope that helps.
 
Last edited:

brianhiatt

Member
2009-12-14 11:44 pm
Anyone willing to help out? Need help with the BOM template calculations. I am just learning so I have a few questions: I am using the following transformer: linberg transformer: Y236752 which is 330 va, 35 + 35 secondaries.

For D1-D8 lost here, if I go for the items indicated as the digi-key p/n they seem like they are enough for my intended 35v rails.

For RS1 & 2 any idea's on what value the resistors should be?
For C1-c8 same question.
Same for CX1 & 2
Same for CS1 & 2

any help would be great and yes I am new to this type of electronics work. Using 35v secondaries because thats what the old PSU I am replacing had. Should make it easier for me.
 
I have a question about the location of the snubber in the PS board circuit. See the circuit diagram at this link:
www.diyaudio.com/forums/images/diy/store/board-documentation/P-PSU-1V30/P-PSU-1V30-schematic.pdf

The purpose of the snubber is to damp ringing created in the diodes (correct me if I am wrong on this) when they abruptly stop conducting. In that case, wouldn't the snubber be better located closer to the diodes, e.g. before the "optional R" in between the two caps on each rail? If you use those optional resistors, you are forming a low pass RC network that seems to me would remove any high frequency ringing coming arising from rectification anyway.

So what's the skinny on this arrangement? What am I missing here? (not meant as a sarcastic question!)

-Charlie
 
Brian,
That transformer will get you closer to 48V rails. Caps and diodes should be selected for that.

Diodes rated 200V are plenty. Pick the package that suits you.

Caps, this is DIY, we go crazy and max out our cap banks. ;) Search for caps which fit the diameter of the footprint and a 63V rating. (Easy to do at Digikey, Mouser and Newark) 50V is too close to the rail voltage, you want some margin for reliability. If you are height limited, consider than dimension, too Then select caps with the highest capacitance that you can afford. There are other considerations such as current rating and ESR that can come into play. Read the datasheets.

Search for PSU designer 2 and simulate your supply under maximum load (one rail will do) Look at the capacitor currents, and be sure that your chosen caps will have some extra capacity. If you are building a class AB amp for home use, you can usually skip this step if you buy decent caps. High bias class A amps on the other hand deserve this consideration.

Realistically, with class AB you don't need as much capacitance and you can make some tradeoffs between capacitance and current capacity. I have a 30 year old Hafler DH-500 (250 WPC) that has been in nearly daily use, sounds good and has 20,000 uF per rail in large can caps. The caps are obsolete, but their format suggests high current capacity. Some would say that's not enough capacitance for a chip amp. So let your wallet be your guide choosing caps.

Read the snubber design article Charlie linked to, and see if you want to mess with adding snubbers CS1,2, CX1,2. These features are totally optional. You will have a working supply without them.

Charlie, I guess the output snubber is there in case you get ringing caused by capacitor self inductance and the capacitance. There are a full set of snubbers on the rectifier sections, too.
 

Bones13

Member
Paid Member
2006-05-12 3:58 am
Behind the times
As a newbie with SS DIY amps, I have ordered the ACA kit to give it a try. I aspire to build the Aleph J at some point.

My question would be, could I build a separately cased PSU with this set of boards, and use it to power either the ACA or the expected Aleph J. My question more goes to using the 18 volt bipolar supply (the Pass "standard" as far as I can tell for the ACA? Then I could have one PSU, and swap the 2 amps? (assuming I don't try others as well)
 
Yes, you could use this board set to make a pair of 18V supplies for the ACA and then reverse the connection on one side to make it a bipolar supply.

If you want to make an Aleph-J someday, start looking for jfets NOW. Appropriate parts are already very scarce.

As for whether you can make an amp with a separate power supply enclosure, Papa does it on a grand scale.
[IMGDEAD]https://passlabs.com/images/uploads/Product_images/124/xs_color__medium.jpg?1374853843558[/IMGDEAD]
 

Bones13

Member
Paid Member
2006-05-12 3:58 am
Behind the times
I ordered a quad of 2SJ74BL from Spencer just this morning. Are there others I should get nailed down now? I did pre-order the boards at the DIYAudio shop already as well. I am not sure if I will build a "universal" PSU for my projects, but would consider at least trialing it once with the ACA, and compare the 2 amps without a PSU compromise on the ACA side. I would have to overbuild on the transformer side if I want to use the PSU for any of the higher power amps I guess.

Just pondering, and trying to plan for re-use of components in a logical, efficient manner.

Thanks for the reply,
Michael
 
Yes, you could use this board set to make a pair of 18V supplies for the ACA and then reverse the connection on one side to make it a bipolar supply.

If you want to make an Aleph-J someday, start looking for jfets NOW. Appropriate parts are already very scarce.

As for whether you can make an amp with a separate power supply enclosure, Papa does it on a grand scale.
[IMGDEAD]https://passlabs.com/images/uploads/Product_images/124/xs_color__medium.jpg?1374853843558[/IMGDEAD]


Are there or will there be alternative components for the jfets?? Or will making these boards like the aleph j become obsolete/impossible? Thanks!