THÖRESS F2a11 Integrated Amplifier

SRP: $12999

Our F2a11 Integrated Amplifier utilizes the famous F2a11 vacuum tube in singleended triode operation mode for an output power of 2x6 watts into a 4, 8 or 16 ohm load. As a device with low power output the amplifier is typically meant to drive loudspeakers with moderate to high efficiency with tame impedanz behavior! The F2a11 is a power tube of matchless built quality, exclusively manufactured  by SIEMENS (& HALSKE) in the 1950s and early 1960s, which has been specifically designed for the most demanding industrial applications. It belongs to the famous german so called POSTRÖHREN family of tubes and is best known for its usage in the iconic ancient SIEMENS KLANGFILM cinema amplifiers. When operated in triode mode this extraordinary tube offers excellent sonics on par with the finest classic filamentary triodes such as 300B, 2A3, AD1 or PX25. The amplifier can be employed as a stereophonic power amplifier (in combination with a line or full function preamplifier) in which case the volume controls of the amplifier serve as input attenuators (to match the gain of the amplifier with the gain of the line device with respect to the efficiency of the loudspeaker).

Although reasonably priced, the F2a11 Integrated shares the non-compromise approach with our larger all-tube mono amplifier models (SE300B and SE845). It is by no means an entry-level component, but a state-of-the art device which is likely to outperform any comparable/competitive product regardless of price. The sound of our F2a11 amplifier is powerful, warm, clear and natural. The sonic presentation is of utmost refinement and will easily meet the expectations of even the most critical and experienced music lover.

TUBES

In the driver stages of the amplifier a 12SN7GT double-triode is employed. The 12SN7GT is a medium-gain octal-base tube from the famous ?J5/?SN7/7A4 family with fairly low transconductance developed in the early times of tube electronics. Unarguably one of the most linear amplification devices ever developed in the history of electronic technology and as such is a perfect choice in the context of minimalist zero-feedback circuit design.

BUILT

The amplifier is built with meticulous hand construction using our proven point-topoint wiring techniques, whereas much care has been taken in arranging each aspect of the internal construction to ensure low noise performance, ease of service and the highest reliability for many years to come.

TOPOLOGY

The amplifier is based on a unique minimalist SINGLE-ENDED ZERO-FEEDBACK vacuum tube MOSFET hybrid topology which we call EHT Topology  (E/intakt H/ybrid T/riode. Decidedly ignoring the fact that many music lovers still persistently believe in the myth that balanced technology (and the associated cable configuration with XLR connectors) is generally superior to single-ended concepts. Readers who want to learn more about our view on balanced techniques and our general design approach are encouraged to read the paper (THÖRESS - Behind the Curtain) downloadable on the ABOUT button of our website. 

INPUTS  AND  VOLUME  CONTROL

The amplifier offers 3 line level inputs (3x2 RCA jacks) with equal gain status selectable via rotary dial non the rear panel. High-grade continuously variable potentiometers are employed for separate (manual) volume control of the channels. These parts are made to our specifications by ALPS in Japan to allow for conveniently fine volume adjustment. Each pair of potentiometers is hand-picked from a production batch by careful measurement to ensure equal attenuation characteristics with respect to rotational angle. Hence the slots surrounding the volume knobs are reliable scales for balance adjustment. Notably, it is not possible to install remote volume control on our F2a11 Integrated. Music lovers who consider remote volume control as an indispensable feature are encouraged to take a closer look at our EHT Integrated and our DFAmp.

TRANSFORMERS

The F2a11 Integrated Amplifier is equipped with proprietary output transformers (OPT) of ultimate quality made in-house. These parts allow for precise matching of a 4, 8 or 16 ohm loudspeaker load to the power tube by way of jumpers soldered to the secondary terminals. Furthermore, the mains transformer is also produced inhouse to the highest possible standards. Thus, we can easily customize the amplifier for all kinds of mains voltages, for example for 100Vac (Japan), 120Vac (USA, Canada), 220Vac (South Korea, China, Thailand, Indonesia), 240Vac (UK) or 245 Vac(Australia). Although the mains transformer has been optimized for low leakage and low body noise emission it is mounted to the amplifier chassis via isolation elements in order to eliminate even the slightest interference of residual transformer vibrations with the circuit.

F E A T U R E   O V E R V I E W

• All-Tube Integrated Amplifier with 2x6 watts of output power utilizing the famous Siemens F2a11 Power Pentode in single-ended triode mode and a highly linear 12SN7GT double-triode in the driver stages.
• Minimalist zero-feedback schematic.
• 3 line level inputs (2x3 RCA jacks) selectable via rotary dial on the rear panel.
• High-grade continuously variable potentiometers for separate (manual) volume control of the channels.
• Ultimate C-Core output transformers (OPT) produced in-house. Precise 4, 8, and 16 ohm loudspeaker load matching via jumpers soldered to the secondary terminals of the OPT.
• High-grade electrolytic capacitors made in Germany in the power supply.
• Ultra low noise mains transformer made in-house for 230Vac,  220Vac (SouthKorea, China, Thailand, Indonesia) or 245Vac (Australia), 120Vac (USA, Canada), 100Vac (Japan).
• Full hand construction, point-to-point wiring throughout.
• Nonmagnetic aluminum casework, anodized printing on front and rear panel, powder-coated chassis, and lids.
• Dimensions: 150x595xH330 mm, 330=20 (case feet) +210+100 (power tube over case), 595=575+20 (binding posts).
• Weight 18 Kg.
• Dimensions of the shipping crate 400x950xH460 mm.