'Model 01' Power Amplifier
Design spec:
A compact, efficient power amplifier. Emphasis on simplicity.
Inspiration:
Features
- High power in compact package
Detail
My previous designs lacked any power amplification. Fitting a power amplifier into the same miniature footprint as the other Briarsfield designs is a challenge; dimensions of the concept enclosure are 85mm x 165mm x 165mm HWD, with the sockets on the rear bringing the total depth to around 200mm - still subminiature in size. Regular Class AB is out (at least at anything above a few tens of watts) because of problems removing the heat, realistically this leaves Class D to give acceptable power output from a small case.
Initial design
Rear view (rough render)
In system (rough render)The amplifier has no visible user controls; it is designed to be remotely switched by a separate preamplifier via a link cable. A separate power switch is fitted to the rear panel to allow manual switching if it is used separately. There is a status LED for each channel (concealed in the black portion of the front panel) - envisaged as yellow for normal operation, with flashing yellow or possibly an additional colour to indicate fault condition (loudspeaker short etc.).
The amplifier is Class D, based on a high power NXP IC; intentionally run well below its power capability to improve distortion performance (efficiency is still quite good, around 80%). Output power of the amplifier is envisaged as around 120W RMS/ch into 8 Ohms, 200W into 4 Ohms, limited by the thermal efficiency of the case and the achievable power density of the power supply.
This design does use various unique parts; the structural enclosure is formed by two custom designed heatsinks, sized similarly to commercial 1ºC/W components but with a more aesthetic appearance. The top panel is CNC machined and engraved, with a similarly ventilated bottom panel.
The amplifier is packaged on two tiers; the upper tier houses the power supply, mounted on an aluminium plate - the power supply in the initial draft is a regular linear with a toroidal power transformer, but design of a switched mode supply is intended once past the initial proof of concept stage. The lower tier houses the amplifier assembly PCB.
More soon...
