NEW THÖRESS EHT INTEGRATED AMPLIFIER

THÖRESS is very pleased to announce the introduction of the (8.950 EUR) Hybrid Triode Integrated Amplifier. “Our new amplifier offers 20 watts of output power per channel (into a 6 ohm load) combined with low output resistance. Such providing excellent drive capability for normal speakers with medium to low efficiency or with critically low impedance which may present a challenge for our all-tube, single-ended triode power amplifiers. While offering the same level of ultimate sonic excellence obtainable from the later devices! It is based on a unique minimalist non-balanced (single-ended), zero-feedback vacuum tube MOSFET hybrid topology. Decidedly ignoring the fact that many music lovers seem to persistently believe in the myth that balanced technology (and the associated XLR connectors and cable configuration) is generally superior over the non-balanced one.”

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 the respective button of our website. Our circuit consists of a vacuum tube gain stage (6J5GT single-triode) driving a single-ended, unity gain MOSFET output buffer operated at high idle current. The EHT topology, as we call it after E.INTAKT-H.YBRID-T.RIODE (single-ended hybrid triode), allows to fully exploit and mate the most desirable characteristics of both the vacuum tube and solid state devices determined by their very nature.

Our EHT Integrated provides 4 inputs with equal gain status (RCA jacks) for line- level program sources, selectable by means of a rotary switch, mounted on the rear panel near the input jacks, driven by the corresponding front knob via metal spindle.

Furthermore, the amplifier comprises a custom designed remote volume control presented with typical THÖRESS style and attention to detail.

Our EHT Integrated is built with meticulous hand construction using our proven point-to-point hard 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.

At the start of the planning and research stages for the Integrated, specific design criteria were established. The new amplifier would obviously have to meet the highest requirements for sonics (such as our F2a11 Integrated Amplifier), it would have to be reasonably constructible and of reasonable size, and it would have to provide a power output well in excess of 10 watts per channel so that it could adequately drive a typical medium-efficiency loudspeaker. After some consideration, it seemed impossible to construct such an amplifier based on an all-tube approach. The EHT topology finally proved to be the best way to achieve our objectives. We are pleased to report that the end result is an integrated amplifier which provides a level of ultimate sonic excellence comparable to our classic all-tube amplifier components.

Analysis easily shows that the EHT principle represents the PUREST form of all possible single-ended triode power amplifier configurations !

Specifically, it can be shown that a higher output power can be more easily obtained with the EHT than with the all-tube single-ended triode amplification principle, without compromising sound quality. Simply because in the former case the critical output stage incorporating a power tube driven (step-down) output transformer (the typical all-tube impedance matching output arrangement) can be completely omited. As a result, the voltage swing required from the driver stage is up to 10 times (!!!) lover for an EHT configuration compared to an all-tube topology resulting in a proportional reduction in over-all distortion for a given power output. This crucial insight was the basis for our pursuit of the described hybrid concept and finally resulted in the launch of our EHT Integrated and, later on, the EHT Mono Blocks.

In spite of its obvious advantages, elegance and extremely high sonic capability, the EHT concept has never been utilized in a serial audio product before, as far as we know. Probably due to its low power efficiency and rather tricky implementation.

  

Our EHT Integrated Amplifier operates with complete thermal stability (inspite of the total absence of negative feed-back) and is fully short-proof at the outputs without the aid of any sound degrading protection circuitry. Moreover, a switch-on delay device (often found in commonly constructed solid state or hybrid amplifiers) is also omitted simply because no disturbing noise or dangerous signal is being developed at the outputs when the amplifier is powered on or off. Attributs which further underline and justify our purist design concept.

As it is the case with all THÖRESS amplifier components, the EHT Integrated is equipped with a mains transformer produced in-house to ensure the highest possible quality and reliability. This component features a dual-coil arrangement on a large tape wound cut core (C-core) and is deadly quiet, of course. In order to eliminate even the slightest interference of residual transformer vibrations with the circuit this part is mounted to the chassis via isolation elements. The fact that all power transformers are produced in-house enables us to readily make dedicated power transformers for all kinds of mains voltages such as 100Vac (Japan), 220Vac (South-Korea, China Mainland, Thailand, Russia, Indonesia) and 245Vac (Australia).

• Vacuum tube MOSFET hybrid integrated amplifier offering 15 watts of output power per channel into a 6 ohm speaker load; utilizing 2 x 6J5GT vacuum tubes.
• Non-balanced/single-ended, class-A, zero-feedback operation.
• Based on our unique EHT (EINTAKT-HYBRID-TRIODE) schematic: single- ended triode gain stage driving a unity-gain single-ended MOSFET output
• buffer operated at high idle current.
• Offering the same level of ultimate sonic excellence as known from no-
• compromise all-tube single-ended triode amplifiers.
• While leaving exotic, costly power tubes out of the play.
• Excellent driving capabilities for critical speaker loads due to very low
• output resistance (high damping factor).
• Total avoidance of any sound degrading protection circuitry.
• 4 inputs with equal gain (RCA jacks) selectable via rotary switch.
• Remote volume control via motor driven dual potentiometer with excellent channel balance and very low angle sensitivity to allow for conveniently fine volume adjustment.
• Full hand construction; point-to-point wiring throughout.
• Ultra low noise, dual coil C-Core mains transformer, made in-house.
• High grade electrolytic capacitors made in Germany employed in the power
• supply.
• Mains voltage 230Vac/115Vac (via jumper settings), customizable for
• 100Vac (Japan), 220Vac (South-Korea, Thailand, Russia, China Mainland),
• and 245Vac (Australia).
• Nonmagnetic aluminum casework; anodized printing on front and rear
• panel; powder-coated lids.
• Dimensions: 434x434xH184mm,
• 184=20/casing feet+134+30/tubes over case; weight: 14 Kg.
• Dimensions of the shipping crate: 550 x 550 x 250 mm