I've wanted a ridiculously powerful amplifier for along time and so started what I call the "A" series to create something with 250+ watts output, exemplary specifications
and bullet proof operation. This last requirement proved ellusive - several early "A" series designs went up in smoke! The A8 resolves all of the issues from ealier designs
while still providing in excess of 300W RMS per channel. A unique feature allows the amplifier to run in "bridged" mode where it provides this 300W output, or near class A
with a more modest 75-100W output level.
To achieve such high levels of output power is not trivial. A very robust power supply is needed, and thermal management is critical for long life. This design is more of a
constant voltage style amplifier using a somewhat low split supply of only +/- 35V. High power is achieved by parallel connecting several output devices, which also helps
lower the output impedance and drive more current into the speakers. The deisgn uses no feedback of any kind and yet is unconditionally stable. Frequency response is
DC - 200kHz (-3dB), or can be band limited if desired. Large heatsinks and push-pull speed control fans (speed is fixed, or varies by level or heatsink temp) keep thermals
under control.
In near class A mode things get interesting. Prolonged operation at maximum power gets things hot in a hurry! The protection circuitry will prevent damage but this mode should
be for more initimate listening sessions - not filling the house with sound! Switching between bridged and class-A mode entails a brief moment of silence as the output relays
click open.
The A8 sounds like all solid state amp's - neutral, flat, un-imposing. The massive amount of output power available makes music simply breath taking to hear - clean dynamics,
effortless volume and a sort of richness heard only with very high power amplifiers. While you could cause this amplifier to clip - it's unlikely! The lack of feedback means
TIM / IM distortion is very low, and the amplifiers nearly 3dB of dynamic headroom means it delivers over 600W peak power. Front panel indicators for power supply voltages,
operating mode, protection circuit status and fan speed let you keep tabs on things when pushing the amp hard (like party time - keep the neighbors up!). I added a set of LED
power meters as well to the design example shown in the picture.
Contact me at geoff@bandonelectronics.com if your're interested in this amplifier. This amplifer will be offered as partial or full kit as well.