EWA WB Power Amplifier

EWA WB Power Amplifier

So if the M-100 Turbo S is one of the finest power amplifiers in the world, what is the WB? Good question!


It results from same extreme school of design that is responsible for the largest class A amplifiers ever built, and the power conversion on the International Space Station.

Ladies, gentlemen, and crazy audio-people, we introduce Colin Wonfor's most consummate power amplifier of his career: The EWA WB. 50W class A output, followed by a relentless flow of musical output that is best described as Rolls Royce once described their vehicle's power output: "Adequate".

This amplifier was not going to be produced due to a counter-intuitive discord: It is very expensive, but less powerful than the M-100 Turbo. This amplifier is meant as a statement of intent, it demonstrates what is possible in the real-world with excellent design and very high quality - yet freely available components. And it is not less powerful, it really isn't quite as simple as that... 


Based on the concept of the masterful M-100 series, the WB features much larger power transformers (twin 750va - per channel), an even more sophisticated power supply section, and many very expensive, very highly specified precision components. It produces over eighty of the finest Watts into eight ohms and is able to keep doubling power output levels as the impedance of the loudspeakers halves. It will drive half an ohm to full output all day, quite happily, outputting hundreds of amperes if called upon (fitted with 10A output fuses as standard). It also has extraordinary low output impedance.


The WB features 16 output devices per channel (32 total) following the massive power devices. These are significantly uprated from the M100 T and TS in terms of speed, tolerance and power handling. The Bulk capacitors (now six each channel) are rated at a massive 300,000uF per side, as part of a fully separated dual mono power supply. The entire circuit board is massive, dual layer construction with double the amount of copper as the M-100 series (4oz copper tracks). The voltage rails of the WB circuit run lower than the M-100 series but is capable of much higher current delivery. With larger transformers and capacitors, this circuit is actually capable of 2 KW RMS at the output (just too dangerous to make).


Input: 10KΩ

Power Output (conservatively rated):

  • 80W/8Ω

  • 160W/4Ω

  • 320W/2Ω

  • 640W/1Ω

  • 1280W/0.5Ω

  • ...and probably more.

In excess of 45W class A at the output.

Unique dynamic bias system (responsive to frequency and amplitude) transitions to A/B.

Bandwidth: over 400KHz

Output impedance / DF: Between 2000 and 10,000 (dynamic).

Power consumption: 1W standby / 60W powered, no signal.

430 x 240 x 360mm. 55 Kg (stereo chassis)

DC offset is less than 0.2mV

The output stage is run in A/B and has a SECA drive stage. Eight complementary pairs of transistors per channel rated at xxxxxxxx (lots and lots - details to follow), driven by xxxxxxx (ludicrously over-specified) transistors. The SECA driver is running at 5W. Ultra-fast RF transistors are used to increase stability in the amp under non- normal loads: i.e. a non-resistive speaker with a wicked load line character. 

The WB amplifier is designed to deliver utterly perfect high current amplification into any loudspeaker in the world completely reliably, maintaining the highest pinnacle of detail, timbre, signal to noise ratio and practically zero harmonic distortion. It is an instrument grade audio amplifier of the utmost precision and robustness, being massively engineered for sustained periods of heroic performance. It is not a muscle amplifier as such, it lacks the outright power for that. But it will drive any load. Forever.


Power supplies can be made for most countries of the world except those on DC. 



BUILD TIME: Approximately 4-6 weeks.

  • Facebook

CV-19: ABCaudio & EWA continue to fulfil orders throughout CV-19 restrictions. We are taking our time to work hygienically and safely.

All products are carefully cleaned with medical alcohol before packing and shipment. 

Home of the EWA cable system and SECA technology for amplifiers, by Colin Wonfor.  Contact us: info@ABCaudio.biz.  All text and images copyright 2021. ABCaudio, United Kingdom.