“Has Icon Audio founder David Shaw designed the ultimate triode amplifier?”, asks the company’s latest press release. Previewed ICONMB81_monobloc_amplifersat September’s National Audio Show and created to fulfil a personal ambition, these gargantuan amps will be sold in limited numbers as a special edition.

“If I’m completely honest,” says Shaw, “for much of the past year I’ve been building my own birthday present – and this is it!”. After discovering a quantity of ‘new old stock’ Russian GU81 transmitter valves, Shaw began to work on a prototype amplifier that would achieve a long-held goal: to effectively drive any modern low-efficiency high-end speaker to realistic levels.

At 260 mm tall, 100 mm in diameter and weighing in at 1 kg, the GU81 is a BIG valve. Although the GU81 remains in production, Shaw still favoured the ‘new old stock’ valves for the MB81.

Shaw has long been a fan of triode operation believing it the purest form of valve amplification. But triodes typically have a downside too: limited power output, which to overcome presents real a design challenge.  Says Shaw, “Our pursuit for making ever-better amplifiers often leads us into uncharted territory. This is such an example and it’s been a genuine labour of love. I’ve spent many, many months designing and listening, listening and redesigning.”

In the Icon Audio MB81, Shaw has produced a triode monoblock that can deliver an astonishing amount of power into even the most demanding of loads. These massive amps are about 50% bigger than the current Icon flagship MB845MkIIm and weigh around 100 kg per pair.  The specification is impressive: 250 watts RMS continuous output into an 8 ohm load whilst “complex” tertiary output transformers minimise distortion while allowing “unbeatable bass power and authority”.

“Following our work with other big triodes, we wanted to build an amplifier that would deliver plenty of power to drive the largest inefficient speakers with ease in pure triode mode, in very large rooms,” explains Shaw.

“Although many large speakers are generally efficient,” he adds, “their complex crossovers full of capacitors and inductors often present a difficult load for an amplifier, especially if it’s running with less than ideal power.”

 

Icon Audio believe the MB81 to be the world’s first ever push-pull GU81 amplifier. While it was initially developed as a personal gift for Shaw himself, he plans to produce a small number for sale as a very special limited edition. “This is probably the most amazing amplifier we’ve ever made,” says Shaw, “so it would seem churlish not to share it”.

Price will be £12,500 a pair.

 

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