THÖRESS Full Function Integrated ""Super"" Preamplifier Instruction Manual

THÖRESS

Full Function Integrated "Super" Preamplifier

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INSTRUCTION MANUAL

Thank you for purchasing the THÖRESS Full Function “Super” Preamplifier. We
believe our versatile preamplifier to offer the highest possible sonic performance from
both the line and the phono section while preserving a state-of-the-art signal-to-noise
ratio. It is a reference device which will easily measure up to the expectations of even the
most critical and experienced music enthusiast or professional user. Please read the
following explanations and instructions carefully to get the most out of your preamplifier.

PHONO INPUTS AND VERSIONS

The "Super" is available in 3 Version differing only in the circuitry of the phono section
to suit particular types of cartridges in terms of input sensitivity (gain) and cartridge load.
Each version provides 3 phono inputs P1, P2 and P3 selectable with the source dial on
the faceplate. Please note, that detailed information concerning cartridges and vinyl
reproduction in general may be found in the manual of our Phono Enhancer. The
Versions are as follows:

Version 1:
This version offers exceptionally high phono stage gain and customized cartridge loading
on P1, P2 and P3 to make these inputs suitable for low-output, low internal resistance
MC cartridges. Cartridge loading is achieved by means of standard axial lead resistors
soldered to tags adjacent to the phono jacks. These load values are factory preset to 100
Ohms, a value that is suitable for most low-output MC cartridges. Other resistor values
can be preset on request, and these values can be changed by the user whenever it is
required.

The cartridge load values preset on the high-gain MC phono inputs P1, P2 and P3 of
version 1 are printed on the rim of the rear panel for reference.

On these phono inputs any dual-coil low-output dedicated mono MC cartridge can be
used without restriction, the Audio Technica AT33-Mono, the Lyra Dorian Mono or Lyra
Helikon Mono and the excellent Dynavector DV-1s-Mono being examples of such high
grade dedicated dual-coil mono cartridges (all of which are omniflexible).

It is possible to mix stereophonic and dual-coil dedicated mono MC cartridges on
any of the high-gain MC phono inputs of version 1 without further adaptation.

However, if a single-coil low-output (dedicated mono) MC cartridge is to be used on
these (stereophonic) phono inputs and it is intended for dual-speaker-mono listening,
precautions must be taken to "double" the mono signal in such way as to avoid hum.
Please see the relevant chapter below for more details on using such cartridges. Examples
of current production single-coil low-output MC cartridges are the dedicated mono
cartridges made in Japan by Miyajima Lab, all models of which employ monoflexible
styluses. A monoflexible stylus has zero vertical compliance and is therefore suitable for
tracking of mono grooves only. If a cartridges with monoflexible stylus is accidentally
used on a stereophonic record it will instantly destroy its grooves as stereo grooves are
modulated laterally and vertically.

Be warned - monoflexible (mono) cartridges can seriously harm stereo grooves !

It should be pointed out, that any omniflexible dedicated (microgroove) mono cartridge is
able to read out stereo grooves without harming the grooves and converts the separated
signals from the two channels (coded into one single groove) back into a consistent mono
signal. Interestingly, the "monophonized" version of a stereophonic record obtained by
tracking with a high grade omniflexible mono cartridge can sound very appealing. On the
other hand, any stereophonic cartridge is able to read out both early and second­generation monophonic microgrooves faithfully and will output two identical signals on
each of its channels. Please recal, that more useful information concerning cartridges and
vinyl reproduction in general may be found in the manual of our Phono Enhancer
downloadable from our website.

Version 2:
Here the inputs P1, P2 and P3 are suitable for medium-ouput MC or MI cartridges
(medium phono stage gain). Each input is loaded at 47K.

Version 3:
In this version the phono circuitry is designed to make P1, P2 and P3 suitable for
ordinary "loud" MM or MI cartridges (low phono stage gain) and accordingly are loaded
with 47K. Of course, low-output (low internal resistance) MC cartridges may be used on
any low gain phono input of this version with the aid of an external step-up transformer.

Please note that, it is NOT possible to mix different kinds of cartridges (such as MC
and MM) on the inputs P1, P2 and P3 (of any version) as they all feed the same fixed
phono circuit optimized for one particular type of phono cartridge regarding input
sensitivity (gain) and load requirements.

LINE INPUTS

Besides the phono inputs P1, P2 and P3 our preamplifier offers two inputs CD1 and CD2
for high-output line level sources such as CD/DVD players or sound cards. One
additional line input HP for classical low-output line level sources such as a tape recorder
or a phono stage is provided. If our Full Function Preamplifier is to be used for line
amplification of our Parametric Phono Equalizer (the Enhancer) or another external
phono device, it is advisable to use the input labelled HP (rather than CD1 or CD2) for
optimal sonic results, especially when the device is based on a tube design.

OUTPUTS

To maximize versatility, the preamp includes two paralleled main outputs. Importantly,
the output resistance at the main outputs is low enough to drive long interconnect cables
and power amplifiers with an input impedance as low as 10,000 ohms without
compromising sound quality. It is thus possible to simultaneously drive a power amplifier
AND the solid state power amplifier of an “active” subwoofer without further adaptation.
The paralleled main outputs may also serve for proper signal doubling if a single-coil
(mono) cartridge is used on one of the phono inputs for dual-speaker mono listening in
the way described in the relevant chapter.

Moreover, a monitor output Q for the chosen source is provided. As the output signal of
the internal phono section will appear at the Q-output as soon as one of the phono inputs
P1, P2 or P3 has been switched active, this output allows the internal phono section of
our preamplifier to be used with high impedance line inputs of other preamplifiers.
Again, the output resistance at Q is low enough to drive long interconnect cables without
compromising sound quality. However, if the input resistances of the line input is
considerably lower than 100K it may be necessary to increase the value of the coupling
capacitors at the output of the phono section, if bass response at the very low end of the
audio band is not to be compromised. At this point only a modest capacitor value has
been employed for coupling in order to obtain a certain amount of attenuation of any
subsonic artifacts present in the phono signal, as it may occur with warped records.

If the phono section of the "Super" is to be used with an external line preamplifier
via the Q output - it is advisable to use a high impedance line input for optimal sonic
results.

USING SINGLE-COIL (MONO) CARTRIDGES ON STEREOPHONIC EQUIPMENT

When both inputs of a stereophonic phono preamplifier are wired to a single-coil
generator cartridge in attempt to create signal doubling to allow for dual-speaker mono
reproduction it is impossible to avoid a conductive connection between "left ground" and
"right ground" of the (non-symmetric) phono circuit and, as a result, unwanted ground
loops are formed.

Single-coil (mono) cartridges will cause residual hum due to ground loops when they
are wired to feed both inputs of a stereophonic preamplifier (with non-symmetric
circuitry) in an attempt to double the mono signal at the phono input for dual­speaker-mono listening !

To overcome this problem the signal should be doubled at the point of output rather than
attempting to accomplish this earlier in the signal path. The paralleled main output jacks
can be used to conveniently achieve this aim in the following manner. Only the right
channel of the phono section should be fed by the single-coil generator via a customized
monophonic tonearm cable, whilst the corresponding left input should be short-circuited
directly at the jack with the help of a RCA plug internally soldered to suit this purpose. If