MB90 MkIIm KT150 version Mono Blocks (pair)


SKU: MB902m150

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The new Tung Sol KT150 valve seems to have taken the Hi Fi world by storm! Now available in the Icon Audio MB90 mono-blocks.

Read the latest review by Hi Fi News. MB90 MkIIm KT150 review Hi Fi News March 2014

Icon Audio’s upgraded version of our MB90 power amplifier has several improvements including circuit and cosmetic improvements. Most importantly a built in bias meter greatly simplifies keeping your amplifier in peak performance. Previously you had to pay attention to numbers. Now if the pointer is on the black mark, it’s correct. Very easy!
The MB90 MK IIm is a very high performance power amplifier specifically designed to work in Triode and Ultralinear mode depending upon your preference and power needs. It can drive the very best of speakers with ease. Using only four output valves the running cost and maintenance is very easy as the valves are run well within their maximum ratings
The front end is inspired by the famous British “Leak/Mullard” designs of the 1950s. This gives a very smooth musical quality to the high power available, making them very versatile in their application. Our unique big Tertiary wound “LDT” transformers give you true high end performance in every way: Dynamics. Macro Dynamics. Depth. Bandwidth. Purity. Warmth.


New features are:

  • New KT120 design
  • Easy Bias system
  • True Triode performance
  • Icon Audio LDT transformers
  • Larger power supply
  • Valve regulated for stability
  • Output increased from 100 to 110 Watts
  • Increased power bandwidth
  • Copper alloy top plate
  • More “Pure Class A” power


This amplifier is an ideal replacement for a larger transistor amplifier, for someone who wants a modern “fast” sounding amplifier that will still give that “warmth” and lack of fatigue that transistors cannot give you.


Specifications and Features


  • Comprehensive manual supplied
  • All hand wired point to point
  • Class A, all Triode front end
  • Output Ultralinear (110W) or Triode (60W) switchable*
  • 4x KT120 matched valves (per pair)
  • 2x 6SL7 2x 6SN7 driving valves (per pair)
  • Signal to noise level -90db
  • Frequency response 20hz-20kHz +0 – 0.5db
  • THD typically less than 0.1% 1khz
  • 4 & 8 ohm loudspeaker taps
  • Beautiful valve cover included in the price
  • SCR hi fi audio capacitors
  • Silver plated pure copper PTFE audio cable
  • Tertiary winding output transformers
  • Big custom wound PSU with Choke
  • Gold plated Input & speaker terminals
  • 450mv (high) & 950mv (low) input sensitivity.
  • 230/240volts 200watts approx
  • Consumption: 38w standby, 88w quiescent, 200w Max
  • C E, ROHS


Size in mm W200, D500, H220 (222 inc cover), 21kg ea (Specifications subject to change)


Information about earlier model MB90s

Beautiful Versatile Affordable

Designed by David Shaw, founder of Icon Audio. Whilst their highly acclaimed Stereo 60 sets new standards for performance, the new MB90 is a more traditional 3 stage design, the front end is based on the Leak 20/50/60 amplifiers. Icon Audio chose to use the older bigger 6SN7 and 6SL7 driver valves from the early 1940’s. These have a reputation for a richer more textured sound, reliability, and a very long life. This combination of traditional design, excellent valves, audiophile components, hard wired, no PCB, custom transformers, massive choke regulated power supply with beautiful looks all add up to a stunning combination!

The power output stage uses the super GEC KT88/KT90 probably the greatest all round hi fi valve, operating in both “Ultralinear”(100w) and Triode mode (50w) to give the maximum choice of operating conditions. Effectively giving you two amplifiers in one! 100 watts of valve power is easily comparable with 200 watts of transistor power and will drive almost any sensitivity of speakers well, leaving plenty of headroom for dynamics and low distortion. The large custom wound transformers are able to deliver very deep bass notes and smooth clean treble.

Close attention has been paid to the large power supply using eight large capacitors and a large “choke” in a traditional “Pi” configuration. This gives a very low source impedance with a huge reserve of power available for large transients without clipping.

This combination gives a very smooth and detailed sound stage which works well to bring out the colour and texture of older recordings and whilst not overemphasising the harshness of many modern digital recordings. This makes for a very easy to live with amplifier that has the power to control modern speakers.

Surprisingly from such big amplifiers is how well they perform at low powers. Their agility and detailed texture of strings and vocals is quite astounding.

A new feature of the MB90 is the high and low sensitivity. This enables MB90s to work with both “Passive” and conventional pre amplifiers. This is not done by the usual attenuation which increases noise and reduces quality, but genuinely changes the sensitivity of the input.

Another new feature of the MB90s is the power saving “Warm up/Standby” switch. This prevents valve cathode stripping during start-up and enables the amplifier to remain in standby on low power without wasting valuable valve life or electricity (only 38w). The amplifiers will then start instantly, fully warmed up.

The brand new design features polished stainless steel chassis, 20 mm solid alloy front panel. And their famous stainless steel and Plexiglas valve cover to create a stunning visual impression. On the scales at 50Kg (pair) this amplifier is no lightweight in quality or performance and should give many years of excellent service.

As each amplifier is prepared  in Leicester, Icon Audio can offer a range of upgrades including their unique HT delay, premium and “new old stock” valves, the superb Jensen “oil in paper” capacitors.

As a small company Icon Audio make customer service a priority. Valve amplifiers do need a little more TLC than transistors, but the sonic benefits are more than worth it.

Specifications and Features:

•- Comprehensive manual supplied

-• Full instructions for valve change included

- All hand wired point to point

-• No printed circuit board to ‘colour’ sound

-• Class A, all Triode front end

-• Output circuit Ultralinear or Triode switchable*

-• 4x KT150 precisely matched for best performance

-• 2x 6SL7 first stage valve

-• 2x 6SN7 phase inverter valves

-• Standby switch to prevent cathode stripping on startup

-• Standby switch to save valve life and power only 35w

-• Optional automatic HT delay to prevent cathode stripping

-• 100w RMS continuous per channel

-• 50 Watts RMS in Triode mode

-• Signal to noise level -90db

-• Freq response better than 20hz-20kHz +0 – 0.5db

-• Total harmonic distortion typically less than 0.1% 1khz

-• 4 & 8 ohm loudspeaker taps

-• Japanese steel EI transformers with low oxygen copper

-• Attractive valve cover included in the price

-• High quality 2W metal film, & wire-wound resistors

-• Blue LED mains indicator

-• Polypropylene audio capacitors

-• Silver TEFLON audio cable

-• Custom hand wound output transformers

-• Big custom wound PSU Choke

-• Ceramic valve holders for minimum leakage

-• Centre tapped heater circuit for minimum hum

-• ‘Soft start’ device incorporated

-• Gold plated Input & speaker terminals

-• 400mv (high) & 1200mv (low) input sensitivity.

-• 230/240volts 200watts approx

-• Consumption: 38w standby, 88w quiescent, 200w Max

-• C E, ROHS, WEEE compliant where applicable

-• Size in mm W200, D500, H205 (222 inc cover), 20kg pr (overall. Allow space for connections and ventilation)


(Specifications subject to change, errors & omissions excepted. General 04/04/08)


MB 90 MK II Leaflet

MB90 MkIIm KT150 review Hi Fi News March 2014


SKU MB902m150
Shipping Weight 40.0000kg
Shipping Width 0.570m
Shipping Height 0.360m
Shipping Length 0.620m
Shipping Cubic 0.127224000m3

1 Year Warranty

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