24Vdc DIY power supply?

audioclass · 19802

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Offline earwaxxer

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Reply #15 on: July 14, 2012, 12:41:48 PM
I was thinking that too. I have a t-amp that comes with a 30V laser printer switcher. It sounded pretty darn good compared to battery. I bit more of an 'edge'. Kind of like good redbook vs. the same in 24/96, although about half the difference.

Eric
Emotiva XPA-2, Magnepan MMG (mod), Quickie (mod), JRiver, Wyrd4sound uLink, Schiit Gungnir, JPS Digital power cord, MIT power cord, JPS Labs ultraconductor wire throughout, HSU sub. powered by Crown.

Offline Grainger49

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Reply #16 on: July 15, 2012, 11:27:39 AM
Ok, I finished the sketch and scanned it.  Hopefully it is not too big for this page.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi244.photobucket.com%2Falbums%2Fgg7%2FGrainger49%2FFor%2520Posts%2520Private%2F24voltsupply.jpg&hash=95f7913c69c93442d18fecf3c609a0b1298e9cf2)


Offline audioclass

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Reply #17 on: July 18, 2012, 07:12:30 AM
Thanks a bunch for the schematic.  I'll be trying this in the next couple of weeks once I get back from vacation!

Beau G.

Offline Grainger49

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Reply #18 on: July 18, 2012, 07:40:23 AM
The capacitors can be anything from 220uF to 22,000uF.  The caps after the regulators smaller (I would go with a nice low ESR 220uF maybe just 100uF) because the regulator smooths.


Offline audioclass

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Reply #19 on: July 18, 2012, 08:02:55 AM
Perfect.  Also one question on schematic.  I can't quite tell if there is a connection from the center-tap on the transformer to the center of the rectifier circuit or not.

Should it be this?
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi1248.photobucket.com%2Falbums%2Fhh493%2Fbeaugagne%2Frectifiercircuit1.jpg&hash=f384894721db3dd79760bef7bae40676fcd69289)


Or this?
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi1248.photobucket.com%2Falbums%2Fhh493%2Fbeaugagne%2Frectifiercircuit2.jpg&hash=926b4438744633aa5a6ad4b4452cc465bed721f3)

Beau G.

Offline Grainger49

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Reply #20 on: July 18, 2012, 08:08:36 AM
The first one.  

You are right, the schematic is wrong.  I should have the line to the center of the two bridges eliminated.  I'll correct it and change the link.  (OOOoooo  I get to use my erasing shield again after all these years, I was trained on a drawing board, then Intergraph, Cadam and AutoCad). 

Thanks!
« Last Edit: July 18, 2012, 08:13:33 AM by Grainger49 »


Offline audioclass

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Reply #21 on: July 18, 2012, 08:10:51 AM
Well I think you have it on there correctly, but looks like there might be some eraser marks there and it made it difficult to tell.  No biggy thanks for the quick reply and of course thank you for drawing up the schematic for me in the first place!

Beau G.

Offline audioclass

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Reply #22 on: July 18, 2012, 11:27:39 AM
Is this along the lines of what I'm looking for in a transformer?

http://www.digikey.com/product-detail/en/241-5-24/595-1056-ND/952926

Beau G.

Offline Paul Joppa

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Reply #23 on: July 18, 2012, 11:32:22 AM
You only need one bridge (four diodes).

Paul Joppa

Offline audioclass

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Reply #24 on: July 18, 2012, 11:42:28 AM
I'm no EE so could you elaborate on that a bit?  I'm going off of Grainger's design here using a 12-0-12 transformer and my knowledge bank is pretty empty beyond understanding some BASIC (just enough to troubleshoot simple circuits) DC theory and reading schematics.

Beau G.

Offline Grainger49

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Reply #25 on: July 18, 2012, 11:50:37 AM
Paul is saying you can use a 24V transformer and create a virtual ground.  A pair of matched 1/2 Meg ohm resistors, in series between the two DC legs will create a virtual ground.  Then attach the capacitors and regulators to the positive and negative rails, ground is between them.

Your transformer is 24V rated at 1/2 amp.  So if that is enough current for the load it is fine.


Offline audioclass

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Reply #26 on: July 18, 2012, 12:16:58 PM
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi1248.photobucket.com%2Falbums%2Fhh493%2Fbeaugagne%2Frectifierfullwave.jpg&hash=5a3e7159e42f6172db1e814e2b7241f483a3da82)

This is the design then?  Are there any disadvantages to using this method to rectify instead of the two bridges?

Beau G.

Offline Grainger49

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Reply #27 on: July 18, 2012, 12:22:08 PM
Ok, I looked up the unit and it uses a chip that draws 4.2mA quiescent.  So any power supply you build will be more than it needs.  The above transformer you linked will do well.

What you have drawn will be fine.  The dual rectifiers might have more separation, might not.


Offline audioclass

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Reply #28 on: July 18, 2012, 12:24:50 PM
Oh wow, so I could go to a smaller transformer in an attempt to save some space then?  Say 100mA or less?  The 500ma would be considered overkill then most likely?

As for the bridges, maybe I'll build both and see which sounds better.  I'm sure I could find a buyer for the second one :D

Beau G.

Offline Paul Joppa

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Reply #29 on: July 18, 2012, 12:54:50 PM
The dual bridges will go up in smoke. You don't need a "virtual ground" - the center tap is the ground, assuming you are looking for +12v and -12v.

I can't believe it - I googled a half dozen different sets of keywords and couldn't find the simple design - and found lots of incorrect stuff. It's crazy.

Here's the circuit.

Paul Joppa

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