FFPre Full Function Preamplifier

FFPre
FULL Function Preamplifier

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The THÖRESS Full Function Preamplifier (FFPre) is a versatile vacuum tube preamplifier incorporating a state-of-the-art line control amplifier (2x12J5GT tubes) and a ground-breaking tube phono equalizer (2x12JGT+2xPC86 tubes) in one chassis.

The phono section of the FFPre provides MC amplification with highly accurate (fixed) RIAA de-emphasis and excellent signal-to-noise performance in a purely active operation mode (without involving step-up transformer gain). The phono section is by no means an afterthought or add-on to the line section but a state-of- the-art device, fully dedicated to maximum performance on par with the ultimate sonic capabilities of our Parametric Phono Equalizer (with tone selectors in RIAA position).

The amplifier is entirely based on SINGLE-ENDED ZERO-FEEDBACK schematics. Decidedly ignoring the fact that many music lovers persistently believe in the myth that balanced technology (and the associated cable configuration with XLR connectors) is generally superior over 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) available on request. In view of our commitment to single-ended design principles, the exclusive use of RCA jacks for signal input and output was obligatory.

The amplifier is built with meticulous hand construction using our proven point-to- point wiring techniques. Much care has been taken in arranging each aspect of the internal construction to ensure highest reliability, low noise performance and ease of service for many years to come. The FFPre is an ultimate high-end component and as such a worthy complement to our all-tube or EHT based mono amplifiers. The sonic presentation of the amplifier is of utmost refinement in line and phono mode and thus will easily measure up to the highest expectations of every discerning music lover.  

INPUTS

The FFPre comprises a MC gain phono and three on-the-fly selectable phono inputs (P1/P2/P3) of equal gain status (65dB at 1kHz) yet different cartridge loading. Alternatively, the FFPre is available with MM gain phono section (45dB at 1kHz) on demand. The standard cartridge load pattern assigned with the phono inputs of 3XMC and 3xMM units are

(P1, P2, P3)=(100, 200, 500) ohms and (P1, P2, P3)=(47K, 47K, 47K)

respectively. Other cartridge load values can be easily installed on request.

The cartridge load values installed on the inputs of 3xMC units are printed on the rim of the rear panel for reference!

It is not possible to implement MM and MC phono gain simultaneously!

Furthermore, the amplifier provides three line inputs (RCA jacks) with different gain and input impedance characteristics as described below.

Normal Line Gain

The gain on inputs 6 is 26dB (20-times). This input presents a comparatively high input impedance of 80.000 ohm to the connected program source and is suitable for classic line level sources such as phono pre-amplifiers, tape machines or tuners.

Low Line Gain

Inputs 4 and 5 offer a lower gain of 18dB (8-times, minus 8dB compared to input 6) and are meant for modern high-output digital sources such as CD or DVD players, streamers, or DAC-s. The input impedance on these inputs is 30.000 ohms.

Summarizing, the gain pattern on the inputs is

(MC, MC, MC; 18, 18; 26) dB and (MM, MM, MM; 18, 18; 26) dB

on 3xMC and 3xMM units respectively. Other gain patterns can be easily implemented on demand, for example

(MC, MC, MC; 10, 10; 18) dB or (MM, MM, MM; 18; 26, 26) dB.

The input selector of the FFPre is implemented (in the classic way) with the aid of a rotary switch mounted near the input terminals driven by a front knob via extension shaft.

VOLUME CONTROL

High-grade continuously variable single potentiometers are employed for separate (manual) volume control of the channels. These parts are made (in Japan by ALPS) to our specifications so as to allow for conveniently fine volume adjustment (low angle sensitivity). Each pair of potentiometers are hand-picked from a large production batch by careful measurement to ensure equal attenuation characteristics (0.3dB tolerance) with respect to angle of rotation (thus the volume knob scales are a reliable reference for channel balance). It is not possible to install remote volume control on the FFPre! Music lovers who consider remote volume control as an indispensable feature are encouraged to take a look at our Dual Function or EHT Integrated Amplifier.

OUTPUTS

The output impedance of the line section is sufficiently low (around 300 ohms) to simultaneously drive long cable lines and power amplifiers with an input impedance as low as 10.000 ohms without compromising sound quality. The 3dB-down frequency under 10.000 ohm loading is still well below the audio band (lower than 5Hz, line output coupling capacitor 3.3MFD). The outputs of the line section
terminate in a twin output (2x2 RCA jacks pairwise connected in parallel). It is thus possible to simultaneously drive a power amplifier and an active sub-woofer without further adaptation. The twin output of the FFPre is also useful for proper dual- channel mono playback installation with SINGLE-COIL cartridges as described in the
user manual.

Furthermore, the FFPre comprises a pass-through output (QUELLE) for the activated input. Hence the internal phono section of the FFPre can be conveniently tapped and combined with external line or integrated amplifiers.

MAINS TRANSFORMER

The FFPre is equipped with a proprietary mains transformer produced in-house to ensure the highest possible quality. This part has been specifically designed for low body noise emission and low leakage. Nevertheless, it is mounted to the chassis via isolation elements in order to eliminate even the slightest interference of residual transformer vibrations with the circuit. Since the mains transformer is produced in- house we can easily built transformers for all kinds of mains voltages on demand, for example for 100Vac (Japan), 220Vac (South-Korea, China, Thailand, Indonesia) or 245Vac (Australia).

• Reference grade vacuum tube line control amplifier and state-of-the-art vacuum tube phono equalizer within one chassis.
• Purely active MC gain phono section (70dB@1KHz) with excellent signal-to-noise performance (no built-in step-up transformers). Alternatively, MM gain (45dB@1KHz) can be installed in the phono section on request.
• Highly accurate RIAA equalization (passive de-emphasis implementation).
• Minimalist single-ended zero-feedback schematics throughout.
• Six inputs (3 phono + 3 line) with gain pattern (MC, MC, MC; 18, 18; 26) dB.
• Channel-separate manual volume control via high-grade continuously-variable
rotary potentiometers with low angle sensitivity (conveniently fine volume
adjustment).
• 2x line outputs with low output impedance.
• Pass-through output for the active input.
• Ultra low noise and leakage mains transformer produced in-house for 230Vac
(115Vac via jumper setting), 100Vac (Japan), 120Vac (USA, Canada), 220Vac
(South Korea, China, Thailand, Indonesia), 240Vac (UK) or 245 Vac (Australia).
• Full hand construction, point-to-point wiring throughout.
• Nonmagnetic aluminum casework, anodized printing on front and rear panel,
powder-coated lids.
• Dimensions: 434x434x154 mm, 154=134+20 (feet).
• Dimensions of the shipping box: 650x650x350 mm, weight 11.5 Kg.