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Instruction Manual Covering: 

 

Stereo 40 MK IIIm 

EL34 KT88

 

 

 

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

EarlIier gloss version pictured with SG KT88 and upgraded driver valves 

Contents 

 

1 Introduction & Final Inspection 

 

2 Quick Set Up Guide 

 

3 Connecting inputs & outputs 

 

4 Getting the best out of your amplifier 

 

5 Trouble Shooting 

 

6 Bias Checking & Valve Replacement 

 

7 Specifications  

 

8 Packing and Shipping 

 

 

 

1 Introduction 

 

Thank  you  for  purchasing  the 

Stereo  40  MKIII

.  A 

great  deal  of  care  has  been  taken  in  the  design, 
selection  of  components  and  production  of  this 
amplifier.  We  are  sure  that  you  will  hear  the 
difference. 

 

In  order  to  get  the  best  out  of  your  amplifier, 
please  read  the  enclosed  notes.  Even  if  you  are 
experienced with Hi Fi 

please read the ‘quick set 

up  guide’. 

Should  you  be  uncertain  about 

anything  to  do  with  your  amplifier  please  contact 
us for advice. 
Valve  (or  Tube)  amplifiers  do  the  same  job  as  a 
solid state amplifier, but they do it differently. And 
whilst  solid  state  specifications  look  good  on 
paper  even  quite  modest  valve  amplifiers  can 
have a richer, more textured sound. Your ears will 
have  become  accustomed  to  your  old  amplifier. 
Sometimes  it  may  take  some  hours  before  your 
ears attune themselves to the new sound. 
Your  source,  loudspeakers  and  room  acoustics 
will  also  affect  the  sound  before  it  finally  reaches 
your ear. Some people find a small adjustment in 
re  positioning  their  speakers  can  help  too.  The 
weakest  link  will  always  affect  the  final  results 

when  making  judgements.  Not  all  recordings  are 
‘equal’!  Therefore  an  amplifier  which  faithfully 
reproduces  the  input  signal  will  also  reproduce 
imperfections  in  the  tonal  balance  and  the 
recording itself. Setting up and judgements should 
be made with a ‘clean’ well balanced recording. 

 

The 

Stereo  40  MKIII

  is  a  push-pull  Ultralinear 

stereo  power  amp,  capable  of  running  in  either 
pentode ultralinear or pure triode mode, using the 
excellent EL34 or KT88* valves in fixed bias. The 
driver  and  phase  splitting  is  all  triode.  The  pre-
amp is a high quality ‘Passive’ circuit using silver 
audio  cable  and  an  ALPS  volume  control.  It  is 
sensitive  enough  to  be  used  with  all  modern 
source  equipment  having  an  output  of  250mv  or 
greater.  Its  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 sounding.  

*This 

model 

may 

be 

used 

with 

EL34/6CA7/KT77/KT66/KT88/6550 

 

          IMPORTANT! 

THIS MANUAL CONTAINS 
ESSENTIAL HEALTH & SAFETY 
INFORMATION FOR YOU AND 
YOUR AMPLIFIER. PLEASE 
READ & KEEP SAFE AND 
REFER TO IF NECESSARY 

Summary of Contents for Stereo 40 MK IIIm

Page 1: ...ttune themselves to the new sound Your source loudspeakers and room acoustics will also affect the sound before it finally reaches your ear Some people find a small adjustment in re positioning their speakers can help too The weakest link will always affect the final results when making judgements Not all recordings are equal Therefore an amplifier which faithfully reproduces the input signal will...

Page 2: ...l wiring check Check Triode mode Run min 6 hour test Check inputs tape monitor Output Valve Bias level mv Sound Quality Channel Balance Valve Microphony Valve Seating Hum level left right mv RF Test LED brightness Serial No sticker and recorded Mains voltage 110 230 240V IEC Mains Fuse 1 6A UK Plug fuse 3A A Remote Control Function Sales invoice Bottom label Credit card receipt Customer survey for...

Page 3: ...there are any unpleasant sounds coming from the speakers switch off and refer to the Trouble Shooting section or contact Icon Audio The GZ34 5AR4 valve rectifier acts as a HT delay on switch on If you do not intend to use the amplifier for a few hours you can switch into standby when it will use minimal power and be ready for use instantly In standby you may hear low distorted sound from the speak...

Page 4: ...ections will ensure a good connection whilst minimising the risk of shorts In our experience valve amplifiers are very tolerant of loudspeaker cables therefore the benefits of very exotic cables may be wasted But this is personal taste Icon Audio or your dealer will advise you As all cables have losses keeping the speaker cables short is best It may be better and be cheaper to re arrange your room...

Page 5: ...bles the valves to be fully warmed and ready to use the instant you put the standby switch down In the standby position the amplifier is only using about 50 of normal power It also enables a healthy cloud of electrons to build up around the hot cathode Also it allows the silver getter inside the valve to mop up any gas that has built up inside and therefore keep the vacuum hard for best performanc...

Page 6: ...event damage numbering them with a marker from left to right as you do so in order that that may be replaced in the same position They should be well packed in cardboard foam or similar and returned to Icon Audio for testing Valves are very rugged if packed properly Mains Supply This amplifier is hard wired to work on 230 240v ac The transformer may easily be re configured for 110 120v ac Contact ...

Page 7: ...rmance and power may be reduced Replacements may be obtained from Icon Audio The 274B is not strong enough for the ST40 arcing and premature failure is likely Explanation RMS watts Do not literally exist But this figure is based upon the RMS voltage output V R Push Pull is a very elegant way of virtually cancelling out non linear distortion noise and hum Whilst dramatically increasing the power an...

Page 8: ...d within three days of receipt This amplifier is designed for normal domestic 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 8 Packing Instructions It is essential that the original box and packing be kept in good condition as this provides vital protection du...

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