First PSU, got a question

[lnh]

I'm building a PSU that will run multiple boards eventually, but I'm wondering at what point do I NEED to split the PSU into multiple parallel units (if at all)? Each board will of course have it's own set of power supply decoupling caps. The power supply is a regulated, snubberized +-30V.

These are the options I've come up with:
1. Run all boards in parallel after the PSU (after the snubber network)
2. Run all boards in parallel with their own snubber networks (after the regulators)
3. Run all boards in parallel with their own regulator circuits, but with one set of rectifiers
4. Run individual power supplies, just paralleled off the transformer


What would be the best way to do this, and what are the problems associated with the other options listed above (why wouldn't you choose them)?

[AndrewT]

Decide first on how you plan to create your Main Audio Ground (MAG).
This may determine which of those options for PSU cannot work.

Now decide how you plan to connect all your exposed conductive parts to the Safety Earth. This may rule out all your other options, or if you are lucky only one remains.

Read Davenport !!!!!!
The information is already on the Forum.
Get used to using "search".

[lnh]

Andrew:
I did try searching, but it's not exactly a standard phrase that's easy to search for...I went through a couple hundred returned threads before deciding to just post in here.
For the grounds: each amp will have it's own central grounding point, which in turn will be connected together at a star ground point coming off the power supply. Off of the star ground will come the connection to the Safety Earth through the standard rectifier/cap/resistor network. The input connections and speaker ground terminals will go to the star ground too (independently).


In thinking about this more I really should rephrase my question:
Using 1 psu to power multiple boards, are there any obvious noise issues that I will possibly encounter if proper star grounding is used? It is a snubberized, regulated psu:



The only big difference is I used different values for the UAR and LAR, and prebuilt rectifiers.

[AndrewT]

If you adopt "G" as your MAG or star ground then all your amps must share this common point. That severely limits your choice of connecting multiple channels together. They are not isolated, as in a pair (or more) of Monoblocks.

Note the length of wire between G and the connection between the smoothing/stability enhancing/decoupling caps.
This "length" is very important. Do not take your Audio Ground nor any Audio Ground to the connection between the caps.

I think according to a detailed article on the Forum on wiring up PSUs that the main smoothing C1 & C2 are connected to the wrong location.
My interpretation is that bottom of C1 goes to the bottom of C7. You then need to break the -ve connection between C1 & C3.
Similarly C2 goes to C8 after you break C2 to C4.
Unfortunately I can't recall the author's name.

[lnh]

Ok. I'm searching for the article that you're referencing...haven't found it quite yet.

Each board's IC does have decoupling capacitors on the input and output (0.1uF and 100uF on each side). Does this provide enough isolation from the other boards?

For the star ground...I will not be making the star ground on the psu per se, it will most likely be about 2-4inches away from the psu pcb.


In the mean time, I'll keep reading

[idjoel2000]

hello, maybe this is off topic but i don't want to make a new thread just for asking one question. so here we go

let say i have 12VAC 1.25A output dual secondary transformer, and i connect the outputs like this:


will i get a single output of 12VAC 2.5A on the secondary stage? thanks in advance

[lnh]

Yes you will.

[AndrewT]

But, be very careful.
With 4windings (8 ends) on that transformer, just one pair of ends swapped and the transformer could appear like a short circuit.

You must use some form of protection to prevent you doing damage.
The bulb tester is ideal for checking out a transformer and whether it is correctly wired up.

[buzzforb]

i I believe Andrew wrote the grounding article.

[AndrewT]

Don't be silly. I never invent anything worth publishing.

I research and throw away the chaff. What's left becomes useful, eventually.