Thöress EHT Integrated Amplifier
Copyright 2020 © Troels Gravesen

Good fortune let me have the Thöress EHT for test some days and it's a daunting task putting together some impressions, because this is really a very special piece of equipment.
The Thöress EHT is a non-feedback single-ended-triode/single-ended Mosfet hybrid amplifier delivering some 18-25 watts depending on speaker impedance. EHT = Eintakt Hybrid Triode.

You can find all the basics here and I won't go through something already done:

The amplifier is also available as monos and you can find a review here:

Thöress website (the EHT not present at website):

My friend, from whom I borrowed the amplifier, asked Reinhard Thöress directly about the power capability and here's his response:
Output Power EHT Integrated:
The EHT Integrated outputs about Uput=34Voltpp into a Z=8 ohm load.
The calculated output power is Pout=SQR(Upp)/(8xZ)=34x34/8x8=18 Watt (per channel).
THD stays below 1 % close to the clipping point in spite the single-ended zero-feedback topology !!!
Assuming that the EHT outputs the same voltage into Z=6 ohms, we get Pout=34x34/8x6=25 WpCH.

My set-up was two-fold:

1: Kuzma/StabiR/4Point9/AnnaD - or Jelco TK850S/My Sonic Lab EMINENT EX + van den Hul The Grail phono stage + Thöress EHT + experimental 4-way loudspeaker, with 15" bass and 92 dB sensitivity, the bass driven from Hypex FA501 leaving an 8" midbass, midrange and tweeter to the Thöress, quite a manageable task for as little as ~15 watts.  

2: Denon DP67L/Moerch DP6/My Sonic Lab EMINENT EX + van den Hul The Grail phono stage + Thöress EHT + Faital 3WC-15 (picture below).

Apart from some hum problems with the 1st set-up, which was temporarily and I never found out why, the Thöress EHT worked without any problems. My reference system you can find here:

System 1:
Initially I ran the entire speaker including the 15" bass driver from the Thöress, as the speaker has a very benign impedance with a minimum of 3.3 Ohm and maximum 6 Ohms. A very easy load and 92 dB sensitivity.
The inability of the Thöress to truly engage the 15" bass driver soon became evident and I added a Hypex FA501 driven from high-level input as there is no line level output from the Thöress. The bass works below 80 Hz, so really doesn't add to the sound as such, only the power needed to make a kick drum sound like it should.
Some 10 years ago I has two PSE 6C33 power amps and the constructor at some point suggested some mosfet auto bias circuitry and I had the best and most holographic midrange ever! However, only for a few hours and the mosfet went up in smoke and I never got it working again and gave it up.
The Thöress brought back this experience. The soundstage was truly the most transparent and holographic I have ever had in my living room and there was a timbre fidelity, a slight edginess to the clarinet that was all of a sudden gone and it was all so addictive and mentally disturbing I went for a 3 day biking trip at the west coast of Jutland to clear my mind of any auditive memory by the clean air coming from the North Sea. After that I was ready to go back home and listen.

What first struck me by coming home was that I would tune the midrange driver in my #1 system, handling 340-5000 Hz, differently with the Thöress. I would probably take the upper-mid/lower-treble down some 1 dB to better the tonal balance. From previous experiences I know this indicated a little too low power from the Thöress for this 92 dB system, even when it only had to run the upper-bass/mid/tweeter section. Too low power may turn the upper-mid a little too dominant and taking the Thöress to my system #2 confirmed this observation where the 96 dB sensitivity regained the tonal balance I like.
For system #1 the 40 watt monos would probably do better, but we would need the pre-amplifier as well - and we're talking a substantial amount of money, some 34 kEUR in total. The integrated here is "only" 8950 EUR.

Testing the Thöress with the Faital 3WC-15 also made it very clear that if you want a kick drum with some live feeling, look elsewhere unless you have some very high-efficiency horn-loaded smaller bass driver. This amp doesn't like a 15" driver in a vented box, even at 96 dB sensitivity. Switching to my usual EAR-868 line stage (still with The Grail phono stage) + EAR-861 32 wpc tube amp brought back the kick drum to what it should be like.
Again from my workshop system the Thöress would bring me that magic holographic soundstage, although I didn't find it as different from the EAR gear as when I tested it first time, rather a different way of presentation. The Thöress is more of the cool presenter, adding close to nothing and truthfully telling you what you feed it, no more, no less, where the EAR gear is better portraying the dynamic aspects of the recording, but also adding minor coulouration, albeit very pleasing to the ear. "Pick your poison" really doesn't go with the Thöress because it seems to add almost nothing.
A "straight wire with gain" is an old saying credited Stewart Hegeman from Harmon Kardon for the Citation line of products. Should I nominate a product for such an award the Thöress EHT would be a candidate - at least until something better comes along, and that would be the same thing, just with more power, e.g. the mono-block versions.


Click images below to view large.

This amp is made in Germany and so is the volume control.
Should you have trouble with Lauter and Leiser, learn German!

I couldn't help taking the Thöress to the basement for a photo shoot and here's the result.



My workshop set-up with 96 dB speakers.




If you think an ALPS potmeter ruins the show, try this amp.









The Thöress running some prototype 4-way speakers with the van den Hul The Grail phono stage and Kuzma turntable.
Don't ask about the speakers. Client work.