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Instruction Manual for: 

 

MB 30m Amplifiers 

 

 

Shown with upgraded driver valves 

Contents 

 

 

1 Introduction & final inspection 

 

2 Quick set up guide 

 

3 Connecting inputs & outputs 

 

4 Getting the best performance 

 

5 Trouble shooting 

 

6 Bias adjustment 

 

7 Valve replacement  

 

8 Specifications 

 

9 Guarantee 

 

10 Packing instructions 

 

1 Introduction 

 

Thank you for purchasing the 

MB30m

Designed by David Shaw in Leicester. These pure 
valve mono block amplifiers are the result of years 
of careful design and listening tests with a wide 
range of speakers. The amplifiers are hand built 
using carefully selected audiophile components. The 
transformers are our own unique LDT Tertiary hand 
wound design hand wound using low oxygen copper 
and special Japanese long grain iron. Each amplifier 
is completed in Leicester, then valved, carefully 
commissioned and tweaked for best performance. 
In order to get the best out of your amplifier, please 
read the “SET UP” notes. These contain important 
information about the correct operation and safety. 
Should you be uncertain about anything please 
contact your dealer or one of our team. 
Valve amplifiers do need a little more attention than 
their solid-state counterparts, but the sonic results 
are well worth it. In this manual we have tried to 
include everything that you need to know. Please let 

us know if you find any errors or feel that we have 
missed anything out. 
The 

MB30m 

is a Single Ended (one output 

valve) triode/UL power amplifier designed for the 
excellent new KT120 power output valves. Many SE 
amplifiers are of low power which limits the choice of 
speaker. The new KT120 valve has enabled us to 
develop an amplifier which has three times the 
power of a single 300B, The MB30 will give ample 
volume with most popular loudspeakers in most 
situations, with a smoothness and richness that is 
often lacking with push-pull designs. 
MB30s operate in “fixed-bias” mode which gives 
maximum power, cooler running and low distortion. 
The MB30s are sensitive enough to be used with 
any pre-amplifier or passive in most situations. Their 
simplicity coupled with point to point hand wiring 
without the use of printed circuit boards results in an 
open euphoric sound that is wonderfully detailed 
and warm. You MUST occasionally check the bias 
this is easy with the built in meter. 

Summary of Contents for MB30m

Page 1: ...out anything please contact your dealer or one of our team Valve amplifiers do need a little more attention than their solid state counterparts but the sonic results are well worth it In this manual we have tried to include everything that you need to know Please let us know if you find any errors or feel that we have missed anything out The MB30m is a Single Ended one output valve triode UL power...

Page 2: ...libration ma Run min 10 hour test Check input Output Valve Bias level v Sound Quality Channel Balance Valve Microphony Valve Seating Hum level L R mv RF Test LED brightness Serial No sticker and recorded Mains voltage 110 120 230 240V IEC Mains Fuse A Soft Start Fitted N A Sales invoice Bottom label Credit card receipt Customer survey form Bias meter Transformer Protection N A Upgrades Output valv...

Page 3: ...sensitive to noise so therefore may be placed close to each other similar to a conventional power amplifier Or alternatively place adjacent to each loudspeaker in order to keep the loudspeaker cable to a minimum They should be placed on a flat surface to allow a gap underneath to aid ventilation ...

Page 4: ...eutral terminal and Green Yellow to Earth terminal 6 SWITCH ON The meter should light up and a visible glow may be seen inside the valves when viewed from certain angles After about one minute the amplifier should now be working With the pre amp volume control set to minimum there should be no sound coming from the speakers except a barely discernible hum If there are any unpleasant sounds coming ...

Page 5: ...t of phase with the sound stage inside out with reduced bass If you are unable to check this or confirm the polarity e g if you have built in wiring a test disc will be helpful If you are bi wiring you can independently use either 4 or 8 ohms for the bass and treble Many modern smaller speakers use a 4 ohm unit If in doubt the heaviest base is the best match depending upon preference and again 4 o...

Page 6: ...gher volumes may be because one of the KT120 valves failing A symptom of this could be unable to bias properly Refer to an engineer or to Icon Audio 3 Hum Problems If you experience hum try disconnecting the input if it clears it is NOT the amplifier but some cause external to the MB30m and further advice should be sought from your dealer or Icon Audio By elimination find out which unit is causing...

Page 7: ...d box with a note detailing the problem which valves you suspect and your contact details We will then contact you with the test results Possible visible valve faults Not all valve faults are visible but KT120s 6SN7s and GZ34s valves should not be used if 1 The silver getter material has turned white or is disappearing air leak 2 The valve rattles excessively a slight rattle is normal 3 There are ...

Page 8: ...lease contact us first 8 Specification Features 100 Pure Class A output power Class A all Triode front end KT120 60w beam pentode output valve 6SN7 CV181 double triodes 1st stage valve Valve rectifier GZ34 5AR4 Output power Triode 16w 11 35v 8 Ohms Ultralinear 27w 14 7v 8 Ohm Oversized choke regulated power supply for both driver and output stage Our own unique designed tertiary wound output trans...

Page 9: ...omestic hi fi use It is not guaranteed for commercial Public Address use or use in other situations The guarantee becomes void if the unit has been modified in any way not approved by Icon Audio 10 Packing Instructions It is essential that the original box and packing be kept in good condition as this provides vital protection from damage during transit Please do not write on box but use removable...

Page 10: ...istor of around 5 10KΩ will speed this up and check that the HT voltage has discharged Amplifier dead Check the 20mm mains fuse in the IEC socket at rear of the amplifier if dead there is a spare included Or the fuse in the plug if applicable If not either check in line power switch fuse adjacent to IEC socket 230v to 115v Conversion Take the precautions as above It is necessary to change the prim...

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