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Based on B&O's own graphs, most bench testers would find little reason to modify anything. Unlike firms which perhaps lack in-house chops to author a superior traditional amplifier, Simon Lee has had many in his catalogue over the years. And he continues to do so. His present adoption of off-the-shelf class D modules signals a few possible scenarios. 1/ For the established DP1 chassis, the available real estate and desired output power demanded class D and B&O simply made for the best solution. 2/ For the intended sell price Simon couldn't design a superior class A/B amplifier. 3/ Regardless of price and size, for him class D by way of the 250ASX2 board had come of age.
Simon would be neither first nor last. By CES 2012 Theta Digital had introduced their new $12.000/pr Prometheus class D monos [left] which are based on Bruno Putzeys' new nCore board. That's an ultra performance next-gen Hypex/uCD development [Bruno's technology demonstrator amp which isn't for sale is shown at right].
Meanwhile Mark O'Brien of US valve audio firm Rogue Audio had used the same CES to launch the Medusa and Hydra hybrid tube/class D amplifiers [lower left].
Adriano Franco Vecino of Audrilabs had emailed me about his new Novachord class A/D amp just prior to the show: "I’m an audio designer and member of the AES Audio Engineering Society. It’s been almost 9 years since I first listened to the Brazilian Audiopax Model 88 amplifier. I must confess to feeling choked by how close it came to live music. I thus decided to become an audio designer like Mr. Eduardo de Lima. He and I are close friends now.
After years of research and investigation I showed him my hand papers in 2008. Now it was his turn to be amazed. He acknowledged that it was the first time he met someone who had developed different mathematical expressions and models only to reach the same deeper understanding. After that discovery we grew closer than ever but by 2009 I radically modified my focus when analog class D amplification piqued my attention. I can now claim the world’s first fully hybrid analog class A/D topology." [Devialet might disagree with that claim I thought before I learnt that Franco Vecino meant tubes. He combines a dual-mono 6H30-based active preamp with 250-watt class D power modules - Ed.]
Class D continues to make inroads. That includes designers who previously bet on tubes; upmarket loudspeaker firms like Mårten Design who want their own high-performance electronics; and serious engineers who intertwine it cleverly with other classes of operation. Firms like H2O Audio combine B&O's analog switching modules with a massive traditional power supply to avoid the stock SMPS. The $50.000/pr 500-watt Mark Levinson N°.53 monos with their Crown DNA and massive power supplies go fully proprietary as they should for that price [upper right]. The brilliant reception for his DP1—a Blue Moon Award and Year's Personal Favorites from me, a Reviewer's Choice and year's end Exceptional Value Award from Doug Schneider at SoundStage!—had reconfirmed Simon Lee's circuit design chops. He simply didn't seem the type to reach for ICEpower out of laziness [Eximus S5 prototype at left]. Would he be comfortable to share specifics on his implementation of these boards?
"The input buffer is a 3-stage unity gain affair for wider and deeper staging, more dynamics and higher musicality.
Most ICEpower®-based systems use a single-stage buffer or input transformer. The driver for our ICEpower boards is our own class A fully discrete A3 circuit which already appeared in the DP1. You can see some silver/gold Mundorf wiring between the board and connectors. There is separate fully balanced routing circuitry and the 1Mohm input impedance creates very stable performance regardless of cables or other conditions.
(Some people in the UK were arguing about your comments on the DP1 as a fully discrete circuit. There we misled you, sorry. We meant that the main A3 circuit is fully discrete. We do use OPA627 or similar-grade operational amps as well but no cheap $1 parts. In fact some op amps are superior to discrete parts and also more expensive than discrete components.)"