Thöress 300B Single-Ended Triode Mono Power Amplifier Picture Gallery Download Manual

Our 300B Mono Power Amplifier...

is equipped with the highly regarded 300B power triode
for an output of up to 8 watts into a 4, 8 or 16 ohm
load. The zero-feedback circuit incorporates an
extraordinary single-stage driver topology employing
two EL803S power pentodes operated in triode mode.
The driver stage is so powerful that it could (theoretically)
drive a loudspeaker with ultra-low distortion
on its own.The amplifier is entirely hard-wired,
while every detail of the internal construction
has been given careful attention to ensure
reliability and ease of service.

The sound of the THÖRESS 300B
Mono Power Amplifier is richly textured, clear,
warm, and dynamic, and will easily
measure up to the expectations
of even the most critical and
experienced music enthusiast



Of special importance are several key design features
which provide exceptionally noise-free performance
even when highly sensitiv speakers are in use:

DC heating is provided for the power tube, whereas
any residual hum introduced by the heater circuit
may be balanced out by adjusting a control knob
on the rear panel of the case. Furthermore,
the input sensitivity of the amplifier is relatively low,
so as to keep the preamplifier’s “idle” noise within
inaudible limits. (This design choice has the further
benefit of avoiding the problems of channel
imbalance and sub-optimal frequency response
which often result when the preamplifier’s
potentiometers rest at too low an angle of rotation.)
Also, the mains transformer is mechanically decoupled
from the amplifier case by means of damper units
to prevent residual transformer vibration from
interacting with sensitive parts of the amplifier.

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  1. Reliable output transformer
    with tape-wound cut core.
  2. Precise 4, 8 and 16 Ohm
    loadspeaker load matching.
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Typical for all our mono power amplifiers is
the following no-compromise approach:

Mains transformers, output transformers and filter
chokes are produced in-house to ensure the highest
performance.The output transformers feature tape
wound cut cores (C-cores) and allow for precise
matching of a 4, 8 or 16-ohm load impedance
to the power tube by way of jumpers
soldered to the secondary terminals.
All used rectifier diodes are of
smoothly switching shottky type,
while high grade foil-in-oil
capacitors are used for
the high-tension supply.


  1. Entirely hard-wired.
  2. 230 Vac or 120 Vas mains
    via transformer jumper.
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A Tribute to Professional Equipment from
the Golden Age of the Electronic Tube !