Axiom Home Page Forums General Discussion The Water Cooler Gonna Try Building a 1kW Class D Amp for Only $396

I have fabulous resistance to buying toys, mainly because I can never decide which toy to buy, and oh, it might go on sale, but now it's on sale, maybe I should, maybe I shouldn't, oh look, it's not on sale again...

But he said above even in unbridged mode it would still cut out because of overheating. I guess I'm just confused on if Class D is supposed to be 85-90+ efficient over A or A/B designs which are in the 50% or less range, no case for trapping the heat, and 4 ohm compatible, why the issues?

If there is a good sound improvement, for the price it still is a great dealeo.

Oh, I missed that bit.

Are the heatsinks those little strips of silver metal in the pictures, or were the real heatsinks removed for the pics ?

A class AB (typical amp) with that power rating would have heatsinks the size of your head (ie a lot more than 10x the size of the heatsinks in the pics) wouldn't it ?

Yup, the little strips are the heatsinks.

Yeah, I'd say at least the size of your head, if not two heads.

Looks like the design's been changed a bit on the shipping amps--I see in his pictures that it has RCA jacks (maybe?) on the boards, but yours has screw terminals in those locations.

How'd you wire up the plug to the outlet? That would probably be the thing that would make me the most nervous.

I am guessing moving up to the SDS line might be worth it as this series has a finned heatsink.

Yeah, I was kind of going back and forth on that--like Steve said, don't really need the balanced inputs or the gain knobs, but the heatsink sure would be nice. Not sure if it's $100 premium nice, though.

The heatsinks on all 3 amp boards (CDA, SDS, TI) are all extremely tiny, so I don't think even the SDS amp would have enough heatsink to drive them constantly at these volume levels without forced cooling. The CDA heatsinks measure 1/2" x 1" x 4.25" (a little over 2 cubic inches, the size of two kit-kat bars on top of each other). Looking at the heatsink in my AVR-3806, I'd say it has at least 50x the mass of the heatsink on these boards. The 4-channel amp I built totally assemlbed weighs about 25 lbs, 18 lbs of which is the toroid and 2 lbs for the mounting board. Most of the weight in my AVR-3806 appears to be heatsink (the tranformer is non-toroidal and much smaller).

I have absolutely no regrets on this purchase even with the reduced power output. 100db per channel of quality amplification with no external cooling is nothing to sneeze at, especially at this price and considering how small they are. It will be interesting to see what happens with the addition of more heatink and the addition of a fan or two.

Yes, these came with screw terminals. He can build them with onboard RCA jacks instead, but most people do not want this since they will be putting the amps in an enclosure.



I paralleled the primary of the toroid just as Tom said in the instructions. I used an old power cord I had lying around and cut off the female end. I wired the hot AC line through a 10A slo-blow fuse, to the line side of the primnary, and wired the neutral line to the neutral side of the transformer. Ground cord unused for now, but I would tie that to the chassis. (Warning - BIG pictures below)



On the secondary side, I had no directions for a 4-secondary transformer. So I wired secondaries 1 and 2 like his directions, and secondaries 3 and 4 like his directions. Since I wanted the voltage to remain constant, but with double the current, I connected these two discrete secondaries in parallel to the heavy duty power supply board. Worked great! (I put the electrical tape on the secondaries by the toroid for me to easily identify the wire pairs of the 4 secondaries, they are not really covering anything):