KR Audio Electronics P135 User manual
KR Audio Electronics
User's Manual
P135
©2017 KR Audio Electronics, Ltd.
Description of the preamplifier
This stereo preamplifier is a microprocessor controlled hybrid system with low frequency
triodes in the output stage. The output tubes work in pure Class A with output transformer.
Condition of vacuum tubes is fully regulated by auto-biased circuitry, so no extra adjustment
for power devices is necessary. The output stage is powered by JFET input stage also working
in class A. The amplifier has three unbalanced and one balanced stereo inputs which are
switched by mechanical (reed) relays. Level of output signal is possible to regulate by a
motorized ALPS potentiometer. The preamplifier is equipped with remote control. Both
unbalanced and balanced outputs are available. All electronic parts are carefully selected and
only the best quality components are used in the KR products.
All high quality components used in KR amps are placed in black paited steel chassis. On the
front panel there are four channel buttons and volume knob with LED indicators, , IR-sensor
for remote control, standby switch and status LED light. On the rear panel, you can find mains
switch with socket, mains fuse, mains voltage selector, 4x2 RCA (Cinch) connectors, 2x2 XLR
connectors.
Installing
•Take the device out of the paper shipping crate and place it on a solid and massive base.
•Allow adequate air circulation to prevent internal heat buildup. We do not recommend
placing the preamplifier on bookshelves or in closed cabinets.
•Do not place the unit on surfaces (rugs, blankets, etc.) or near materials (curtains, draperies)
that may block the ventilation slots.
•Do not install the unit near heat sources such as radiators or air ducts, or in places subject to
direct sunlight, excessive dust, mechanical vibration or shock.
•To prevent fire or shock hazard, do not expose the unit to rain or moisture.
•Connecting an audio system to the amplifier: Use shielded audio cables with male RCA
(Cinch) or XLR connectors. Use cables as short as possible to avoid higher levels of hum
and noise.
•Check the setting of the mains voltage selectors on the rear panel and make sure you are
plugging into a correct mains feed.
•To avoid added hum and noise to the signal feed all audio equipment (the preamplifier, CD
player, equalizer, amplifier, etc.) from common mains socket.
•Switch on the mains voltage switch on the rear panel and press the standby switch located
on the front panel. The status LED light will be on (red) and tubes will be heated. In
approximately 10 sec. the light on the volume knob becomes bright red when the pre-
heating cycle is completed and the preamplifier will be ready for your listening enjoyment.
Servicing
•Condition of output tubes
The tubes are set to optimal values by auto-bias circuitry. Their condition is continuously
monitored by a microprocessor. If the status indicator and volume knob LED are lighting
red, the preamplifier including output tubes is fully prepared to use.
•Mains fuse substitution
Disconnect the mains cord and srew out a fuse cap placed near the mains socket with a help
of e.g. small coin. Replace burned fuse with a new one. Use only same type which is on the
label near the mains socket.
•Protection of output devices
The preamplifier is protected against a failure of output vacuum tubes. If a plate current of
output tubes is not in a safe range because of tube failure or signal overloading, the
electronic protection will automatically shut down the preamplifier. The status LED will
start blinking red and the system will be set to standby mode. In this case press a standby
button and after few seconds try to switch on. If the red indicator is still blinking every
time after switching on, it will be necessary to replace the vacuum tubes.
Warranty
The amplifier is covered by the KR Audio Electronics warranty for all parts and labor for total
of two (2) years from date of sale. Tubes are warranted for 12 months from date of sale.
Tampering with the amplifier may void the warranty. All the repairs under warranty will be
done either by the manufacturer or by the manufacturer's authorized service center.
Technical Data
Power Tubes 2 x KR45 triodes
Line Inputs 6 x RCA (Cinch) , 2 x XLR
Line Outputs 2 x RCA (Cinch) , 2 x XLR
Line Input Sensitivity 0.75VRMS / 47kΩ
Output Level 1.5VRMS ( Rload ≥2kΩ)
Balanced Output 2x1.5VRMS ( Rload ≥4kΩ)
Frequency Response 10Hz ÷100KHz (-1dB)
Power requirements 230/115VAC , 50/60 Hz
Power consumption 36VA
Mains Fuse T200mA/T400mA (slow)
Operating temperature 5C°to 40C°
Weight Approx. 6.5Kg
Dimensions including projecting parts and controls (w/h/d)
Approx. 36.5 x 8.5 x 26 cm
Design and specifications are subject to change without notice.
KR Audio Electronics sro,
Nademlejnska 1/600,
198 00 Prague 9, Czech Republic
Tel.: 00420 2 81864217
Fax: 00420 2 81864343
http://www.kraudio.com
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