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Analog Addict 15th January 2008 03:05 PM

48 VDC/10 A power supply looking for an Amp design
Greeting All!

Migrated over here from AK to see if someone might point me in the right direction to find an amplifier design to fit a power supply I recently bought....

here's the Beef...:D

I'm basically looking to try and build an amp to power the low end of a set of Infinity RSIIb's, which can drop to 1 ohm impedance during use. I have a Nak PA-5A II Stasis amp/Hafler DH-500 for the high end. As I understand it, this power supply is good for almost 500 Watts, but I'm really more interested in trading power for higher quality sound. I also have a friend who may be able to lend a hand, including making the PCB's etc....


taj 15th January 2008 04:49 PM

There are plenty of amplifier designs available here that work fine at 48 volts (assuming your supply is bipolar). But to drive a 1-ohm load it's going to require a lot of parallel output transistors (5 pairs?) to handle the current draw.

Is that 48v secondary AC or rectified DC?

Maybe the Delta Audio Leach amp (5 pair version).

FYI: I can't view your links as I'm not a member of that forum.


megajocke 15th January 2008 05:03 PM

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Analog Addict 15th January 2008 05:04 PM

Lemme try this....
Here's a commercial link...

Analog Addict 15th January 2008 05:50 PM

And a picture...(I hope)


Stuart Easson 15th January 2008 06:07 PM

I don't think...'s a bipolar design.

There are plenty of amps that can run from a single ended supply, but the Leach mentioned so far is not among them...

You can 'fake' a bipolar supply using a pair of huge caps and some bleeder resisters etc, but you would have a +/- ~24v supply. Not really a huge limitation if driving 1ohm speakers is your goal, but something to keep in mind.

Using a pair of bridged amps might be possible, since the outputs are then relative to each other, not ground, but AC or balanced input would then also be needed...AlephX springs to mind, or a pair of KSA50s.



ekaerin 15th January 2008 06:07 PM


Guess that supply will work just fine. It's quite large though.
Any single supply amp will work. (Do I dare mention FB-D-Amp).

-48V linear supply, sounds like some ancient telecom supply, in that case the output is likely to be slightly above 50V at lower loads and the output ripple and noise is very low.
Considering the size of the caps the above might be true.

/ Mattias

Analog Addict 15th January 2008 06:26 PM

3rd time the charm???
Some days it doesn't pay to get out of bed....

Analog Addict 15th January 2008 06:26 PM

Good guess...
The power supply came out of a lot of used telecom equipment, along with a couple of Kenwood PR70 -1 and 1A bench top regulated DC power supplies. 0-70 VDC up to 1A, and finely adjustable...

Analog Addict 15th January 2008 06:36 PM

The moderators have finally gotten tired of looking at my boring posts!

Here's another....

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