Thöress 845 Single-Ended Triode Mono Amplifier Picture Gallery Download Manual

The most powerful amplifier of our product line...

is equipped with the highly regarded 845 power triode
and is capable of delivering up to 20 watts of power
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 carefull
attention to ensure reliability and ease of service.

The sound of our “flagship” is of utmost
refinement and will easily measure up to the
expectations of even the most
critical and experienced
music enthusiast.

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Of special importance are
several key design features which provide
exceptionally noise-free performance even
when highly efficient 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.

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  1. Entirely hard-wired.
  2. 230 Vac or 120 Vas mains
    via transformer jumper.
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Internal Construction

THÖRESS...

A Tribute to Professional Equipment from
the Golden Age of the Electronic Tube !