THÖRESS EHT Integrated Amplifier MKII User manual

THÖRESS
Hybrid Triode . Integrated Amplifier
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"EHT Integrated"
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I N S T R U C T I O N M A N U A ..............
Thank you for purchasing the THÖRESS Hybrid Triode Integrated Amplifier!
Our Integrated offers 2x20 watts of output power into a ohm load combined with
very low output resistance (high damping factor). Such providing excellent drive
capability for loudspeakers with medium to low efficiency or with critically low
impedance which may present a challenge for our all-tube single-ended triode
amplifier models.
The amplifier is built with meticulous hand construction using our proven point-to-
point 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. Please read the following explanations
and instructions carefully to get the most out of your EHT Integrated Amplifier!
TUBES
The vacuum tube gain section of the EHT Integrated has been tailored around the
J5GT tube, a highly linear medium-gain octal base triode with fairly low
transconductance from the early times of tube electronics. The amplifier comes with
a set of tubes which have been carefully tested and hand-picked to meet tight
specifications.
The use of tubes with questionable characteristics may lead to a degraded sonic and
signal-to-noise performance. Even serious circuit damage may occur in worst case
scenarios!
BASS BOOST FUNCTIONS
The EHT Integrated Amplifier MKII (launched in October 2022) includes two novel
bass boost presets selectable via a 3-position toggle switch (B1 > boost style-1, B2 >
bass boost style-2). When the switch rests in middle position the tonality of the
amplifier is neutral (flat frequency response).

The bass boost functions are useful for a variety of applications: For equalizing
loudspeaker components with slim bass response or limited bass extension. For
adjusting the bass response of the system to the acoustical conditions of the
listening environment (small loudspeakers in large rooms!). For restoring tonal
imperfections of the listening program (often given by a lack of bass extension). Or
simply for switching to a more full-bodied presentation if one is in the mood for
listening to music in an enriched and laid back way.
FUSE
The EHT Integrated Amplifier draws a current of about 1A (2A) from the 230Vac
(115Vac) mains, corresponding to a power consumption of 230 watts. It is protected
with a
2A slow-blowing 5 20mm fuse
in the power inlet. On rare occasions, the fuse may blow at the switching-on
moment due to the current spike drawn by the mains transformer in this instant.
Should this condition arise more regularly it may be advisable to use a fuse with
slightly higher current rating.
SETUP
To set up the EHT Integrated Amplifier switch off all components of the system and
proceed as follows.
Do not connect the amplifier to the mains until steps 1 to 7 have been taken.
1. Make sure that the frontal power switch (NETZ) rests in OFF (AUS) position.
2. Bring the master power switch on the power inlet module into the ON position.
It is advisable to switch off the amplifier at the power inlet when the unit will not be
used for a longer period of time!
3. Turn the volume control knob to the zero position or at least a very low angle of
rotation.
4. Install the tubes carefully. Hereby ascertain that the guide pin of the tube base is
properly aligned with the notch of the socket.
Never switch on the amplifier unless both tubes have been installed!
Never pull out a tube while the amplifier is powered on!
Never pull out a tube of the socket as long as it is still hot!
Always de-install the tubes and wrap them in their original protection case before
shipping or transporting the amplifier!
5. Bring the amplifier into its final position. Make sure that there is sufficient
clearance around the unit to allow for adequate ventilation.

The EHT Integrated Amplifier is a class-A device which runs hot after a few minutes of
service. It requires adequate ventilation for safe operation!
. Connect the amplifier to the loudspeakers.
7. Connect the amplifier to program sources and/or a phono preamplifier.
8. Connect the amplifier to the mains.
9. Power on the program sources (while the EHT Integrated is still powered off). Wait
until the warm-up process on all these components has come to an end.
10. Power on the EHT Integrated Amplifier.
11. Wait until the unit has warmed-up.
Always switch on the program sources (or phono preamplifier) first and then switch on
the EHT Integrated amplifier, observing a delay of at least 30 seconds!
Never switch a program source (or phono preamplifier) on or off while the EHT
Integrated is powered on!
12. Choose the desired program source with the input selector. Adjust the listening
loudness manually or via remote control. The minimalist volume control module
features only two pushbuttons (volume up, Lauter and volume down, Leiser) and is
powered by 2pcsxAA batteries (not delivered with the unit). The batterie
compartment is locked with a metric size 2.5 Allan screw.
When powering off the system, always switch off the EHT Integrated Amplifier first, then
switch off the other components of the system observing a delay of at least 30 seconds!
Keep the original crate and the tube protection case for later use. They have been
specifically designed for safe transport under rough conditions! Shipping the amplifier in
inadequate packaging will result in catastrophic damages of the unit!
F E A T U R E O V E R V I E W
•Vacuum Tube MOSFET Hybrid Integrated Amplifier with 20 watts of output
power per channel (into a ohm load).
•Driving capability for critical loudspeaker loads due to very low output
impedance (high damping factor).
•Ultimate sonic excellence on par with no-compromise all-tube single-ended
triode amplifiers, yet without involving exotic and costly power tubes.
•Unique minimalist zero-feedback EHT schematic: single-ended triode gain stage
( J5GT tube) driving a unity-gain MOSFET output buffer operated in single-ended
(class-A) mode with high idle current.
•Total avoidance of protection circuitry.
•4 line level inputs (2x4 RCA jacks) with equal gain selectable via rotary dial.
•Remote volume control via high-grade motor driven dual potentiometer with
excellent channel balance and low angle sensitivity.
•High grade electrolytic capacitors made in Germany in the power supply.
•Low noise low leakage dual-coil C-Core mains transformer made in-house for

230Vac (115Vac via jumper setting), 100Vac (Japan), 220Vac (South-Korea, China,
Thailand, Indonesia) or 245Vac (Australia).
•Full hand construction, point-to-point wiring throughout.
•Non-magnetic aluminum casework, anodized printing on front and rear panel,
powder-coated lids.
•Dimensions 434x450x184 mm, 184=20 (feet)+134+30 (tubes over case),
•450=434+1 (speaker binding posts).
•Dimensions of the shipping crate: 50 x 50 x 350 mm, weight 18Kg.
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THÖRESS...
A Tribute to Professional Audio Components
from the Golden Age of the Electronic Tube !
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