Originally Posted By: sirquack

In purchasing my Odyssey Monoblocks some time ago, one of the advantages over other amp designs I was looking at, was that each of my monoblocks has 120,000 microFarad capacitance, for a total of 240,000 uF for both of my m80's.

The new Axiom 1400-8 amplifier has 140,000 uF total for the entire 8 channel amp. Now, I am not totally up on digital versus class A A/B designs, so maybe the more efficient 1400-8 does not require as much capacitance?




Randy. Its important to keep in mind that you are talking about 2 very different amp designs with the Odyessey monos being a Class AB design and the Axiom being based on a Class D design. That presents entirely different sets of tradeoffs and design issues of which capacitor size and array are actually a small part of it.

The articles cited above are very good for describing issues involving Class A or Class AB amps but people should be cautious about making generalizations when discussing other classes of amps.

Class A and AB amps are the most common and can provide excellent audio performance but their achilles heal are that they are energy inefficient which is why they need fans or heat sinks which adds to their weight and size . Typically 40-50% of the energy gets lost as heat which puts alot of stress on internal circuits and components. That energy inefficiency also necessitates the need for somewhat larger caps to deal with energy loss. Some would suggest that larger caps provide better transient performance but I'm on the fence on that one since so much depends on how the circuits and components have been configured from amp to amp.

With Class D switching amps like the Axiom, they are very energy efficient, with the A-1400-8 being close to 95% efficient. The switching circuitry requires very fast voltage response and gate time in order to keep distortion to a minimum, so more smaller caps carefully laid out would be a better design choice. The dynamic power handling of the Axiom amp also means that the power supply rails have to turn on a dime and dump power quickly into the channels demanding more watts. Again smaller caps would be a better choice.

Finally there are size constraints. The A-1400-8 is a small technological marvel and there aren't that many places to fit large caps.
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John