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Old 24th February 2005, 10:35 PM   #1
DaveM is offline DaveM  United States
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Default Aleph X power supply schematic?

I am a newbie and just got my main and driver boards from the group buy. I am now looking for a schematic for a regulated power supply +/- 25 to 30 VDC. Could someone please help. I've been searching the archives and can't seem to find one. I am fairly technically savvy, but I am not in circuit design.

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Dave
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Old 24th February 2005, 10:48 PM   #2
jleaman is offline jleaman  Belgium
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Old 25th February 2005, 12:59 AM   #3
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I never posted an "official" power supply for the Aleph-X because I figured most folks would rather roll their own. Regulated power supplies suit me just fine, but tend to give some people hives. The trick is to have plenty of capacitance after the regulator. Those who hate regulated power supplies usually (if not always) seem to be referring to regulators with little or no capacitance after the regulator. They claim (and if there's no capacitance, they're right) that regulators kill the dynamics.
But it doesn't have to be that way.

Grey
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Old 28th February 2005, 01:33 PM   #4
DaveM is offline DaveM  United States
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Thanks Grey.

I am a total newbie to amp design. I did a similar thing when I got into speaker building. I built a line array with 12 - 6.5's and a ribbon tweeter. Now I decided it was a good idea to build a Pass amp. Ha!! It will take me a while, but I will get there.

I have been re-reading the WIKI and am starting to get a grasp of why I am not finding the responce I was hoping for.

So now I have another question for those who are in on Kari's group buy. What are people intending with these boards. What kind of rail voltage? What power are you expecting? I haven't had time to mess with the excel spreadsheet yet, but this weekend I did get time to sit down with the schematic and find out where my elbow was in relation to my ... well you know.

Thanks

Dave
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Old 28th February 2005, 05:58 PM   #5
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It seems alot will build 100 watts into 8 ohms. It will require 22 volt rails. I will use a toroidal transformer with dual 17 volt secondaries @ 750 VA. I bought them from Victoria Magnetics for $100 each. I am using either some IXYS bridges or some bridges I bought in the fast recovery bridge rectifier group buy. I have not decided which yet. I am using a C only filter with two 75000 microfarad caps per rail, per monoblock.
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Old 28th February 2005, 09:08 PM   #6
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Rules of thumb (I do this to drive the pendants crazy...):
1-Decide your target RMS power into target load
2-Determine what RMS voltage this represents
3-Multiply this by 1.6 and put a plus and minus in front of it--this is your rail voltage
4-Assume as a bare minimum that the amplifier will dissipate three times the RMS output wattage as heat--this will increase if you start going for 4 ohm, 2 ohm, 1 ohm loads...
Double the quiescent heat dissipation--this is the minimum VA for your transformer
5-Use enough output devices to dissipate that heat reliably (corollary: have plenty of heatsinks on hand)
6-Build it and listen...hoist a drink in Nelson's direction
Anyone who wants to complicate things beyond this is welcome to do so. Some people like to sit down and calculate the Vgs losses against the available rail voltage and thermal transfer and cumulative Gate capacitance and...
Egad, I can calculate and build the confounded thing while they're still agonizing over the fifth decimal point. You'll be surprised how close the recipe I gave will get you compared to all the sixteen decimal floating point arithmetic with pepperoni and extra cheese on top spreadsheets. The beauty of my method is that--in a pinch--you can do it on a piece of scratch paper in a short period of time given nothing but your noggin and a few minutes of peace and quiet.

Grey
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Old 28th February 2005, 09:14 PM   #7
jleaman is offline jleaman  Belgium
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What kinda Regulated board do you need ? What is the regulated Voltage out ? I'm working on one right now almost done too..
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Old 28th February 2005, 09:23 PM   #8
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Mr. Rollins

Your no fun.........

Actually...If you can't calulate it in your head, it's not worth it......
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Old 2nd March 2005, 11:49 AM   #9
DaveM is offline DaveM  United States
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J,

I don't have any real power requirements in mind, so I am flexable. My present speakers (due to change with mood or weather) are 95 db efficient. But even with inefficient speakers I never push volumes that require more than 80 or 100 watts. My first inclination after reading the big thread was that 25 volts was where you wanted to be for best performance. At this point the most important thing to me is that it works without letting the smoke out, so any advice is helpfull.

Thanks

Dave
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