Thoress F2A11 Instruction Manual

THÖRESS
F2A11 Stereo Integrated Amplifier
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INSTRUCTION MANUAL
Thank you for purchasing the THÖRESS F2A11 Stereo Integrated Amplifier. This truly
unique tube amplifier offers the music lover the possibility to build a purist setup
consisting solely of a CD/DVD player or sound card, the amplifier itself and a pair of
highly efficient loudspeakers such as our FR20 or 2CD12 speaker models. Of course, the
amplifier may also be combined with a preamplifier, such as our Full Function
Preamplifier or a stand-alone phono stage, in which case a high-gain unit such as our
Phono Enhancer is strongly recommended.
Three line level inputs are provided, selectable with the source dial located at the back of
the case. The volume of each channel is controlled separately via high-grade rotary
potentiometers (custom made by ALPS in Japan). These parts are carefully matched to
ensure precise channel balance with respect to the rotation angle.
Although reasonably priced, the Stereo Integrated employs the highly regarded new-old-
stock Siemens F2A11 beam power tetrode operating single ended triode mode. The
amplifier is hand-made in Germany. It shares the non-compromise approach of the larger
THÖRESS Mono Power Amplifiers and is entirely hard-wired. Every detail of the
internal construction has been carefully considered for reliability and ease of service.
Therefore our smallest amplifier model is by no means an entry level component, but a
puristic state-of-the art device which is likely to be sonically superior to any competitive
product regardless of price and thus will easily measure up to the expectations of even the
most critical and experienced music enthusiast or professional user.

POWER TUBES

The Stereo Integrated is a single ended amplifier equipped with the highly regarded
Siemens F2A11 beam power tetrode operating in triode mode. These new-old-stock
professional grade tubes are known not only for meeting very tight specs and being
extremely reliable, but also for offering excellent subjective sound quality (when
operating triode mode). They are certainly on par with the finest directly-heated triodes
such as the 2A3 or 300B.
The power tubes are biased via low tolerance 220 ohm cathode resistors. The control-grid
bias voltage cannot be trimmed in any way to adjust the idle current of an individual
power tube. This is a very reliable and stable way to achieve grid bias, but it makes it
especially important to use tubes that meet tight specifications. Note that an average