This is my story of how I went when I wanted to build the ultimate bass amp.
Here is the story of “Tower of Power” as they were baptized rather quickly when the project was revealed among the local DIY community.
First of all I wanted two dedicated mono subwoofer amps that bettered the Crown K2s they were to replace.
After having read and heard a lot of positive stuff about these Aussie Amps, I felt they fulfilled my pre defined criteria very well.
Class AB, high power, high damping factor with many output devices and what seemed to be good quality parts.
Second I wanted an unusual design, that also limited the floorspace needed, since my livingroom was already crowded by horns and and electronics.
After a lot of research I landed on building a pair of Holton 800s, but in a vertical arrangement instead of the classic rack style cabinet
By coincidence I came across a pair of huge heatsinks that came from the civilian rocket range at Andøya in Northern Norway, where they´d been part of a huge 150KVA UPS installation.
They were close to ideal, both because of their vertical fin arrangement and their size; 200mm wide and 300mm high with fin depth 70mm
I then started to fiddle around in google sketch up how this could be arranged inside an aluminium tube with convection cooling.
The heatsinks were big enough to house both the amp module and psu pcb´s and even the speaker protection pcb with a little creativity.
A carpenter friend of mine have access to a cnc, so when shown my sketch up drawings, he milled some nice platforms for the power transformers.
They had to have air inlets to make the convection idea work.
Here one is seen with some cool custom heavy duty legs.
This is a 2KVA transformer for the amp module, a solid chunk.
While I was at it I of course had to go for the separate driver stage psu, that required another transformer.
Here you can see it mounted on top of the other and under the supporting board for the heat sink assembly.
Note the big hole that will direct the rising air up through the fins
Below the assy is mounted on the supporting board.
I'm a little lazy and hate drilling, so I used a curtain slide track to spread the pressure evenly over the output devices from the other side.
Here are the black anodized aluminium tubes.
They´re 250mm diameter and 650mm length to be able to house all.
I even had to trim the outer fins on the heatsinks to make enough height for the Elna electrolytics.
Now that everything is planned in detail the assembly was pretty straight forward despite that everything is custom.
Here´s the soft start and a barrier strip for the driver psu ac wires.
Here a close up from below.
Close to first tests.
Had to make a panel for AC inlet, fuseholder and powerswitch
Wanted it all in the bottom, bothe because of “logistics” and I always run ac and dc far apart.
Outer tube on……
Starts to look serious.
The smiley amp initial testing!
And finally on duty.
And the sound is very controlled,tight and fast.
The woofer towers were low passed actively at 75Hz and fills in below a big custom self-designed 3 way horn system with stacked frontloaded JBL 2220B 15 inch from 75-600Hz. Passively higpassed at 600 are TAD4001 in Autotech JMLC 270 horns followed by TAD 2001 in JMLC 1400 horn.sensitivity from 75 is 112db/2,83v, so I really wanted some fast and furious amps to support the low end
And BOY do they deliver! And the convection cooling works like a dream, and the heatsinks never passes 38 Celcius, whatever I throw at these amps.
But I´m a restless bugger so the woofer towers are now replaced by some custom horn with frontloaded 21 inchers from Eighteen sound
An overview of the system that presently rules.
Last but not least I want to thank Anthony for excellent products and superb support during the whole process.
Thxs from Norway
Best
Leif
