| "The Brick" Power Amplifier | ||||||||||||||||||||||||||||||||||
Introducing "The Brick" Specifications Under The Hood Speaker System Introducing "The Brick": The workhorse of this project is undoubtedly the power amplifier units, dubbed (oddly enough) "The Brick", because of it's similarity in appearance to your average house brick. Basically, "The Brick" is a simple, compact and reasonably powered (for it's size) stereo power amplifier available as a kit set from DSE. A visual profile:  Click for a larger image Four of these units are used to drive the speaker system directly from the Hafler Matrix decoder outputs. One for the front channels, another for the rear channels, and one for each LFE channel. (in bridge mode) Specifications:
Under The Hood: "The Brick" is built around two LM1875 power amplifier IC's and a TL072 preamp. The preamp stage provides input buffering and takes care of the signal inversion for bridged mode operation. (The left channel preamp becomes an inverting amplifier which drives the left channel power amp from the right channel input)  Click for a larger image At the back of the enclosure you can see the two LM1875 IC's bolted to the rear panel and finned heatsink, from there they heat the box like a frying pan. The PCB on the far side contains the preamp and power supply circuitry. The transformer is tapped at the 0V, 15V and 30V lugs to give ±15V potentials for running the amplifier IC's. The preamp stage runs from ±12V which is clamped by two 12V zener diodes. Believe it or not, the transformer introduces very little mains hum into the output despite it's proximity to the input circuitry. The bluish/gray paper is elephantide insulation which isolates the transformer primary and switch from the metal housing. Elephantide insulation paper is supposed to fire proof, but thankfully I've never had this demonstrated....  Click for a larger image Speaker System: The speaker system consists four identical "satellite" speakers, (although they really aren't small enough for a satellite system) and two old school paper-cone 12" woofers to handle each LFE channel. I call it a satellite system because the front and rear speaker sets all have a frequency response of 110Hz to 20KHz, which nicely matches the 100Hz low pass filter which drives each LFE channel from the Hafler Matrix decoder. This feature, along with the crossovers built into each 2-way "satellite" speaker increases the systems efficiency by avoiding the power wastage of driving speakers with frequencies which the drivers themselves cannot reproduce. The "Optimus XTS 9 Speaker System" is pictured below.  Click for a larger image
One of the woofers is shown below removed from it's enclosure. The pair of these have managed to separate the jib board ceiling from walls, over the last 5 years.  Click for a larger image
All up, it's not that impressive, I know. Yet few people seem to realise just how much a mere 20W RMS actually is, I know I can't stay in the same room for more than a few minutes.... And I don't believe that raw power is a fair measure of any sound systems capabilities. If you have any comments or questions please don't hesitate to contact me. |
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"The Brick" Power Amplifier - Amplifier overview, speaker system.