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Old 27th April 2006, 02:31 PM   #1
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Default Aleph X Power Supply Design. Needs Help

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I am going to use the same circuit as my power suuply of my Aleph X. If i want to have 20-0--20V coming out at the other end, what is the value of the secondary voltage of my transformer has to be?

Angus
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Old 27th April 2006, 02:46 PM   #2
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Nominally, the DC voltage will be 1/2 your secondary voltage x 1.4 - the diode drop of .6V. A 15-0-15 transformer will get you there with a little bit to spare.

What are you going to power with this? Your chosen diodes are good for 1A and 220 uF seems awfully light for anything audio.
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Old 27th April 2006, 03:30 PM   #3
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This is the newer design.
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Old 27th April 2006, 03:44 PM   #4
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That's the correct way to wire a dual secondary transformer to a single bridge and get split rails.

1.4x secondary - diode drop is what you'd get (nominally)
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Old 28th April 2006, 10:49 AM   #5
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Thanks very much. I will start my Aleph in 2 weeks time. I am scared that it won't work!

Angus
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Old 28th April 2006, 11:11 AM   #6
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Angus,

Is this PSU intended for the Aleph X?

If so, and as Bobellis was pointing out in post #2, the chosen diodes and capacity in the first schematic are not good.

Xavier
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Old 28th April 2006, 11:19 AM   #7
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I assume that you used that schematic and parts designations just as a wiring example, but if that schematic is intended to power an Aleph of any flavor, the diodes and caps need to be orders of magnitude bigger.

For the bridge, either use a 35 A or larger bridge or beefy discretes. NP said he is using BYW99W-200 in the XA series.

Aleph caps should total at least 100,000 uF on each rail. More is better(within reason).
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Old 28th April 2006, 12:22 PM   #8
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I am using a 25A Bridge in a single channel supply and i will use 4 X 47000 uf capacitor.
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Old 28th April 2006, 12:45 PM   #9
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That should be OK, but a little close to the rated current. I use heavier bridges just to be on the safe side, since peak currents will be quite high.

PSU designer says in my upcoming AX supply (68K uF, 0R1, 68KuF, bias at 6A) the peak current will be 30A (15.5A RMS) once steady state conditions are reached. The turn on spike is 165 A. Check your bridge's peak current rating.

PSU Designer is a real eye opener - The first Cap will see 23A peak/15.6A RMS. No more wonders why to use low ESR/ high ripple caps.
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Old 28th April 2006, 09:11 PM   #10
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Angus,

I suggest for your Aleph-X configuration the following :

1000VA toroidal transformer, 18V-0V-18V (ac). This would give you about +/-24V after the rectifiers. Use over-dimensioned rectifiers, as the transient current is very high. Many people here use BYW99W-200, for example. After the first 2 caps (47000uF is fine), use 4 LM338K (2 in parallel for +ve rail, same for-ve rail) to regulate the voltage to +/-20V, and then use the other 2 47000uF caps after that. This is probably the simplest solution to start you off, before you try something more fancy later. The LM338K only gives you 5A each, so you would need 2 per rail to be save. And they would need big heatsinks (dissipates something like 25W each).

Have the look at the following sites :

http://www.tcaas.btinternet.co.uk/jlhnewps.htm
http://www.tcaas.btinternet.co.uk/jlhcapmult.htm

Read all datasheets before you buy anything. : )


Happy building,
Patrick

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