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Old 19th March 2005, 11:59 PM   #1
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Default Please Help! PSU Question

Its my first time out trying to build a PSU and I really would like some feedback on the following, are they safe? Will they work well? etc. etc.

Click the image to open in full size.

Click the image to open in full size.

I need to power 3 amps from a toroid.

Any advice would be appreciated, I can then go back implement the suggestions and then repost the new design ready for further commment and suggestions.
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Old 20th March 2005, 12:49 AM   #2
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The bottom Pic looks good to me..pretty standard setup..

What's up with the "floating" caps on the first pic?
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Old 20th March 2005, 01:00 AM   #3
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Quote:
Originally posted by DigitalJunkie
What's up with the "floating" caps on the first pic?
That would be my mistake.

I'll go back and fix it.

Are the rectifiers wired correctly?

EDIT: Fixed:
Click the image to open in full size.
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Old 20th March 2005, 01:11 AM   #4
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Click the image to open in full size.

What I'm trying to do is to adapt certain aspects of this design by Dejan Veselinovic, into a 3 channel version.

Am I heading in the right direction with the above wiring diagram? I know its missing his RC filter but I thought that would make the diagram look even more messy.
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Old 20th March 2005, 01:21 AM   #5
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Just for simplicity, couldn't you use a bus bar to respectively tie the positive and negative supplies together?

I'm learning myself but it seems to me you're simply tripling the capacitance to accomodate the extra channels. Do you really need to tie each channel to a different cap?
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Old 20th March 2005, 01:38 AM   #6
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Quote:
Originally posted by ultrachrome
Just for simplicity, couldn't you use a bus bar to respectively tie the positive and negative supplies together?
Like this?

Click the image to open in full size.

Quote:
I'm learning myself but it seems to me you're simply tripling the capacitance to accomodate the extra channels. Do you really need to tie each channel to a different cap?
Would something like this be better then?

Click the image to open in full size.

I'm in the same position as you I'm still learning all this and simply experimenting and trying to get things right before I start proper.
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Old 20th March 2005, 01:45 AM   #7
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Default Re: Please Help! PSU Question

Hi,

Quote:
Originally posted by ShinOBIWAN
I need to power 3 amps from a toroid.
That's difficult (ground loop hum and noise).
Make sure you ground them appropriately.


Quote:
Are the rectifiers wired correctly?
Yes, they are.

But I wouldn't bolt all three capacitor sets to the same ground bar.
This joint (between the caps) actually is not the amplifiers ground point.

At first, it's not a point (and it should be).

Furthermore, by connecting all three cap groups together, you have the charge/discharge currents of the right one flowing through the return path of the others, etc.

I think it's better to split the bar into three sections. You could then join them at the ground star point. And where's your PE connection?

Cheers,
Sebastian.
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Old 20th March 2005, 01:50 AM   #8
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You've been posting while I was.

Quote:
Originally posted by ShinOBIWAN
Would something like this be better then?
Yep, this saves splitting the ground bar. You can now directly connect it to the star ground (via a single, thick connection). Perhaps it could improve crosstalk performance to split the three groups, but then you would also need three sets of rectifiers, and then you would actually have built three power supplies...

But still no PE connection? It should either be at the ground star point, or at the input terminals, depending on the rest of your amplifier configuration.

Sebastian.
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Old 20th March 2005, 01:52 AM   #9
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If you're using only one set of rectifiers, your three channels will effectively be in parallel, which means your supply caps will all be in parallel also. This is not necessarily a Bad Thing, since you can now consider a CRC supply circuit. The Pass crowd seems to favour those, so you can search for more info there. A bit of simulation with PSUD shows some benefit in ripple amplitude and spectrum at the cost of a fraction of a dB of maximum power output, a worthwhile tradeoff in my book.


Francois.
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Old 20th March 2005, 01:58 AM   #10
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Quote:
Originally posted by sek
You've been posting while I was.



Yep, this saves splitting the ground bar. You can now directly connect it to the star ground (via a single, thick connection). Perhaps it could improve crosstalk performance to split the three groups, but then you would also need three sets of rectifiers, and then you would actually have built three power supplies...

But still no PE connection? It should either be at the ground star point, or at the input terminals, depending on the rest of your amplifier configuration.

Sebastian.
Thanks Sebastian!

I'm unsure what you mine by a PE connection? Could you eleborate, I'm new to all this so please go steady.

So is this design suitable?
Click the image to open in full size.
Also, I do put the star ground on the ground bar don't I? Then I connect the GND's from all the amps to this point?
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