Icon Audio MB81 PP Valve Mono Bloc Power Amplifiers
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  • Regular price £15,999.00

Our pursuit for making better amplifiers often leads us to places that no one has been before! Here is such an example.

The magnificent 1950’s Russian GU81 transmitting valve has superb audio qualities and is tremendously robust. We were so inspired by our prototype design we decided to have a limited edition production in response to customer requests.

The MB 81 has seemingly unlimited vigour and drive and is capable of reproducing large orchestral works and rock music in a vivid 3D soundstage in vivid warm natural colour.

The result is probably the most amazing amplifier we have ever made in terms of getting 250 watts of “Icon” sound! Reaffirmed by Hi Fi World no less.

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. For example although large speakers are generally efficient their complex crossovers can have lots of capacitors and inductors which present a difficult load for an amplifier, especially if it is running with less than ideal power. It is a curious thing that speaker companies say very little about the amplifiers that their speakers are designed for, yet the intimate synergy between the two is crucial to “make or break” a good sound system.

Have an audition you will not be disappointed!

  • 250w (45v) @ 8 Ω continuous, @1Khz, 2% THD
  • THD 0.5%@100w, 0.1% @8w
  • Pure Class A, pure Triode front end
  • All hand wired point to point
  • Built in “Easy Bias” Meter
  • 1x 6SL7 first stage valves
  • 2x 6SN7 output driver valves
  • 2x EL34 output driver valves (in triode mode)
  • Signal to noise level -100db
  • Damping factor of 3
  • Frequency response 12hz-28kHz -1dB @8v
  • Suitable loudspeakers 4Ω to 16Ω
  • *Low Distortion Tertiary” wound output transformers
  • Solen/SCR Hi Fi quality audio capacitors, upgrades available
  • Jensen copper PIO caps on request
  • Silver plated pure copper PTFE audio cable
  • Gold plated Input & speaker terminals
  • Attractive Plexiglas valve cover supplied
  • Sensitivity: 0.65v (0dB FB), 1v (3.7dB FB), 2.7v (12.4dB FB)
  • No printed circuit board, easy to service
  • Input impedance 100 kΩ
  • 220/240/115 volts 450watts typical, 750w max
  • 5, D66, H38.5cm (40 inc cover), 50kg
  • Packed 2 of 49x81x45cm. 1 of 85x43x46mm Total 136 kg

(Overall dimensions exc cables, allow for good ventilation)

Typical Figures @ 235v Provisional specifications subject to change


For the true valve enthusiast who wants ultimate in power and quality. Our 250w “Goliath” Triode PP power amplifiers for powerful modern speakers in a large room. A unique experience. Come for a listen.

(Specifications subject to change, errors & omissions excepted. General July 2018)

We have several deomonstation areas in both of our branches. Please give us a call on 03435236169 or email support@kronosav.com to enquire about hearing products at your local branch. 

Please always contact us before to make sure the product(s) are available

Express Deliveries

Express Delivery is FREE on all orders over £50. Express Delivery offers delivery in 24-72 hours from time of purchase. We use premium couriers for this service, mainly DPD & Royal Mail. DPD will offer you a one hour window for delivery to make sure someone is at home, or you can reschedule the delivery if no one is around. 

Standard Deliveries

Here at Kronos AV, we have vast experience with e-commerce sales. Making sure that your parcel arrives undamaged is a huge priority for us. That’s why at Kronos AV, we only use premium couriers for all our orders. All our parcels are shipped with DPD or Royal Mail and are always sent Signed For to make sure it gets to the right person. 

If for any reason your parcel does arrived damaged, please get in touch, and we will be happy to get everything resolved for you. We are always on hand to help!


Delivery is FREE on all orders over £50. In order to offer FREE delivery to UK customers, we use several premium couriers to ensure your delivery arrives safe.

Most large orders (over 2kg) ship using DPD or DHL courier and smaller orders (under 2kg) by Royal Mail signed for services.

The most appropriate courier will be chosen for the items ordered to ensure the quickest possible delivery.

We can offer very generous trade in offers across the majority of our product range. 

Why not ask and see how much you HiFi is worth!

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If you have any question, please feel free to call us on 03435236169 or email support@kronosav.com