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Replacing the KT150 Valves
Important: Do not attempt to change the KT150
without reading these notes. Failure to do so could
be both dangerous and damaging to the amplifier.
When replacing valves, we recommend that you use
a "matched pairs", for best performance.
Use only KT150 valves. KT88, 6550, KT120 etc are not
suitable.
Health & safety; High voltages are present inside the
amplifier and on exposed valve sockets when valves
are removed, so take suitable care. It is not
necessary to remove the bottom cover. Beware
valves get hot in operation!
5, Changing valves: You should if possible check the
bias setting before you attempt to change the valve(s), in
order to familiarise yourself with the procedure.
Replace and bias one valve at a time. Remove the first
old valve and fit the replacement. Switch on and
measure and adjust the bias.
Do not allow the reading to go above 95. Don't worry
how low the reading goes this will not cause damage.
Continue in the same way and fit both valves. Do final
adjustment when the amplifier is fully warmed up.
If all is well there should be no more than a barely
detectable hum from the speakers, and the amplifier
should sound OK when tested.
6, If you cannot set up the bias then the valve is probably
faulty. If the valves are brand new, you will need to
check again after approximately 10 & 100 hours, after
that only occasionally or if you suspect a problem.
7, To avoid damage to the amplifier and electric
shock hazard you must use only valves marked
KT150, 6SN7/6N8/CV181 Or that you know to be
direct equivalents. Use only valves which you know to
be new or good condition and test the amplifier
thoroughly before resuming normal use.
8, Replacing the small valves:
These are three 6SN7 valves. None of these requires
any set up procedure. It's just 'plug and play', although
care should be taken when removing and inserting not to
break the centre spigot.
Icon Audio are happy to check your valves Free of
Charge if you send them to us in Leicester. We will also
gladly check you ST30se and re-bias free of charge for
personal callers.
The 3 fuses inside this amplifier are critical safety parts
They should only be replaced with the same type. These
are available without charge (in the UK) from Icon Audio.
Outside the UK postage will be charged.
7 Specification & Features
(Typical conditions @ 230v 50Hz)
• KT150 output valves
• 3x 6SN7 double triodes driver stage
• Low or medium feedback used (L and H)
• Icon designed and manufactured Tertiary wound
output transformers
• Hand wired point to point components
• No printed circuit board
• Ceramic valve bases for low noise/leakage
• 28w RMS Ultralinear @ 1.2% THD low gain
• 28w RMS Ultralinear @ 2% THD high gain
• 18w RMS Triode @ 0.6% THD low gain
• 18w RMS Triode @ 1% THD high gain
• Signal to noise level -84dB ref 28w low gain UL
• Freq. response 30-20kHz +0-0.5db 8w UL low gain
•
Freq. response 30-20kHz +0-0.5db 8w Triode low gain
• 0.4% THD at 8 watts UL and Triode
• Channel balance typically less than 0.1 dB
• 4 and 8 ohms output taps
• Choke regulated power supply
• Supplied with attractive valve cover
• Audiophile quality metal film resistors
• SCR Audiophile polypropylene audio caps
• Optional Jensen copper foil upgrade
• Japanese ALPS volume pot.
• Rubicon/Nichichron power caps.
• Internal wiring using PTFE silver plated cable
• Valves carefully matched for best performance
• Gold plated Input & speaker terminals
• Inputs for CD, Tape, Tuner, Aux, iPhone
• Record loop with monitor switch
• 240mv sensitivity for full output "H" UL/Triode
• 550mv sensitivity for full output "L" UL/Triode
• 220-240volts 50 Hz for EU and UK countries
• 117v 60Hz for USA Canada
• 50 W Standby 180w Min, 220watts max
• IEC SKT 3.0A AS (5A USA) fuse (with spare)
• Internal HT fuse 250ma AS ceramic. (2x spares)
• 380W, 230H, 345D mm Amp overall 21kg
• Carton= 52x44x36cm 28kg packed
• IEC mains lead
• Conforms to CE ROHS and WEEE where applicable
Specification subject to change without notice.
Technical Explanation:
*RMS watts Do not literally exist! But this figure is based upon the RMS
voltage output (V²/R).
*Class A Where the valve is configured to work at near maximum current
without "switching off" at all times even at zero volume. Although this uses
more power and the valves run hotter, shortening their life, this results in a
superior sound without harshness or obvious distortion and is often used in
conjunction with Single Ended Triode designs.
*Single Ended is where only one output (or power) valve is used. Although
relatively inefficient and of lower power than push-pull designs, these
designs offer a very smooth musical sound which many people consider
much easier to listen to than more powerful modern designs.
*Triode a simple valve with only 3 elements, this gives very linear
amplification. Many "pentode" (5 element) valves can also be wired to act as
triode valves.
*Ultralinear (or Distributed Load). This is a true "win-win" output stage
design. Giving 90% of the power of pure Pentode and 90% of the
characteristics of pure Triode valves. But some people (but not all) still
consider the sound slightly inferior to pure triode.
Page 7
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