If you read my CAF 2023 Standout Products post, now you know I wasn’t kidding.
Early Monday morning post-CAF 2023, I met David Cope, proprietor at Stonington, CT-based Old Forge Audio, with an open tailgate and belly full of coffee. In it, the car, went the Thöress EHT Integrated Amplifier, the very one I and maybe you saw in the Old Forge Audio room.
The EHT is a hybrid design, mixing tubes and MOSFETs (in- and out-put) for 20 Watts of power into 6 Ohms.
The amplifier is based on a unique minimalist single-ended zero-feedback vacuum tube MOSFET hybrid topology which we call EHT Topology (E.intakt-H.ybrid-T.riode, Single-Ended Hybrid Triode). The EHT topology consists of a single-ended triode gain stage (6J5GT,12J5GT or 7A4 vacuum tube) followed by a unity gain MOSFET output stage also operated in single-ended Class-A mode with high idle current.
The back panel tells a simple story with 4 single-ended RCA inputs, a single set of speaker binding posts, IEC inlet, and power switch.
From the left we have the power On (Ein) / OFF (Aus) control, Volume, Input selector, and a 3-way toggle switch for the Bass Boost that offers 3 settings where the center position is “Neutral” while B1 and B2 offer different bass boost styles. We shall see/hear what those styles are in the review proper.
I’m looking forward to turning that power knob to Ein.
- Vacuum Tube MOSFET Hybrid Integrated Amplifier with 20 watts of output power per channel (into a 6 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 (6J5GT 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 (2×4 RCA jacks) with equal gain manually selectable via rotary dial.
- Remote volume control via high-grade motor driven dual potentiometer with excellent channel balance and low angle sensitivity (for conveniently fine volume adjustment).
- 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+16 (speaker binding posts).
- Dimensions of the shipping crate: 650 x 650 x 350 mm, weight 18Kg.