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Old 15th February 2006, 08:07 PM   #1
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Default Does a really big PS in an Aleph 30 help drive low impendence loads?

I just finished an Aleph 30. Because I had at hand two Signal 28v by 12a transformers, I used them in the power supply. Since the transformers’ voltages were so high, I implemented a choke input filter which bucks the voltage down to 26.5v rails under load of the Aleph 30. The inductors are 2.5 mh followed by 400,000uf of capacitance.

I took the amp over to a friend’s house and connected it to four pairs of 1970’s vintage (and refurbished) Advent two way speakers. These were the large speakers. To my delight, the Aleph 30 drove all eight speakers effortlessly and to concert hall levels in the small living room. The Aleph 30 was driven by a Norm Tracy X-DAC whose AD811 output buffers were set to a gain of 5. Four speakers were connected in parallel to each channel.

I note that the 60 watt Mcintosh amp which my friend had been using on these speakers was not nearly up to the task…no volume, distortion, out of control speaker cones and thermal cutoff after 15 minutes.

I am wondering if the larger than necessary power supply helped in the driving of four pairs of speakers. Would I have gotten the same results if the power supply was only just adequate to power the Aleph 30?

Thanx Nelson for giving us the plans, what an amp!!
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Old 15th February 2006, 08:19 PM   #2
tja is offline tja  Netherlands
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I don't know what impedance these speakers have, but wouldn't it have been better to parallel two series pairs per channel?

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Old 15th February 2006, 08:53 PM   #3
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Both of those approaches will improve the performance,
the caveat being that as you parallel lots of outputs, the
character of the amp shifts a bit of emphasis to the bottom
from the upper mid and top.
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Old 15th February 2006, 09:20 PM   #4
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thanx for your replies...

but did the large power supply help drive these loads? or do I have a lot of excess power supply capacity.
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Old 15th February 2006, 10:18 PM   #5
Zen Mod is offline Zen Mod  Serbia
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Originally posted by audionut
thanx for your replies...

but did the large power supply help drive these loads? or do I have a lot of excess power supply capacity.

when you do something like this to your amp-there is no "excess power supply capacity".

answer is pretty obvious,or you just like to boast ?

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Old 15th February 2006, 10:38 PM   #6
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Default excess?


You have excess power supply capacity for sure, the nature of these amps is to naturally limit the maximum output current, hence they can't trivially be damaged by driving very low impedance loads, they just don't double up their output power as the load impedance halves. For sane speaker loads this is not a problem, and makes the amps more or less bulletproof.

If you wanted to be able to use more of your huge current reserve you'd need to 'tune' your amps differently. This could be achieved, as previously mentioned, by paralleling more output FETs and then adjusting the idle current and perhaps the AC gain. Of course even bigger heatsinks are then necessary...or perhaps fans...

You don't mention if your amp was already overbuilt, but if you already have large numbers of output FETs on a massive heatsink, you may not need to do more than increase the idle current and AC gain.


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