THÖRESS Full Function . Preamplifier
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“FFPre MKII”
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P R O D U C T D E S C R I P T I O N
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 (2×2 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).F E A T U R E O V E R V I E W
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.
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THÖRESS…
A Tribute to Professional Audio Components
from the Golden Age of the Electronic Tube !
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