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atelier 13 audio

THÖRESS SE-300B Monoblock

"Reinhard Thöress set out to exalt the treasures contained in the Triode tube, through a classic approach that has proven itself and a deliciously Retro look, a sound result unlike any other in its density, its presence, its energy and its realistic spatial presentation, serving all the emotion contained in each recording. Those who are connoisseurs of Valve-halla will be delighted by the Thöress amplifiers and their rare musicality"

A Tribute to Professional Audio Components from the Golden Age of the Vacuum Tube! 

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emotionally expressive ... lyrically beguiling !



300B Single-Ended Triode Mono Power Amplifier

The SE300B Mono Amplifier is an all-tube power amplifier employing the famous 300B filamentary triode in single-ended (Class-A) operation mode for an output of up to 10 watts into a 4, 8 or 16 ohm loudspeaker load.


The amplifier is entirely based on SINGLE-ENDED ZERO-FEEDBACK schematics, decidedly ignoring the fact that many music lovers persistently believe in the myth that balanced technology (and the associated cable configuration with XLR connectors) is generally superior over single-ended concepts. 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 as download on the ABOUT button of our website.


The 300B power tube is excited by an extraordinary single-stage driver employing two EL822/CV2382 power pentodes operated in triode mode with high idle current and works into a tape wound cut core (C-core) output transformer (OPT) which is built in-house to the highest possible standards to ensure ultimate performance. The driver stage is so powerful that it could (theoretically) drive a loudspeaker load with very low distortion on its own whereas the OPT allows for precise matching of a 4, 8 or 16 ohm loudspeaker load to the power tube by way of jumpers soldered to its secondary terminals.


These design choices are to a large extent responsible for the richly textured, clear, warm and dynamic sonic presentation of the amplifier, particularly when combined with high sensitivity-type loudspeakers, or our horn based 2CD12 or underhung-motor based 1D66 loudspeaker.


The amplifier is built with meticulous hand construction using our proven point-topoint 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.


The SE300B Mono Amplifier is an ultimate component and as such a worthy complement to our Dual Function Amplifier or Full Function Preamplifier. It easily outperforms competitive products regardless of price and will certainly measure up to the expectations of even the most critical and experienced music lover.





Specific design choices guarantee low noise operation even when the SE300B mono block is combined with a highly efficient loudspeaker such as our 2CD12 model.

  • Firstly, the 300B power tube is DC heated whereby the cathode point of the amplifier circuit can be balanced with respect to the filament of the given power tube by means of a control knob [ a rotary potentiometer ] on the rear panel. Once the balance adjustment has been carried out, the signal current is distributed uniformly over both ends of the 300B filament, and residual hum due to ripple of the heater supply voltage vanishes [ reaches a minimum ].

  • Secondly, the amplifier has been specifically designed to have a moderate gain [ low input sensitivity ]. This ensures that the idle noise of the line device remains inaudible in all possible scenarios. Notably, this design choice also ensures conveniently fine volume adjustment.





The SE300B mono amplifier is equipped with a mains transformer produced in-house to ensure the highest possible quality and reliability. This part has been optimized for low body noise emission and low leakage.


Nevertheless, it is mounted to the chassis via isolation elements in order to eliminate even the slightest interference of residual transformer vibrations with the circuit. Since the mains transformer is produced in-house we can readily customize the amplifier for all kinds of mains voltages, for example 100Vac (Japan), 120Vac (USA, Canada), 220Vac (South Korea, China, Thailand, Indonesia), 240Vac (UK) or 245 Vac (Australia). particularly when combined with high sensitivity loudspeakers, or with our 2CD12 or 1D66 loudspeaker.

F E A T U R E  O V E R V I E W

  • All-Tube Mono Power Amplifier utilizing the famous filamentary 300B power triode in single-ended operation mode​

  • 2x10 watts of output power

  • Minimalist (pure class-A) zero-feedback schematic

  • Powerful single-stage driver utilizing two CV2382 (EL822) power pentodes operated in triode mode at high idle current


  • High grade foil-in-oil capacitors (made in Germany) in the power supply​​

  • C-core filter choke made in-house


  • Ultimate tape wound cut core (C-core) output transformer with dual-coil winding manufactured in-house

  • Precise 4, 8 and 16 ohm loudspeaker load matching via jumpers soldered setting to the secondary terminals of output transformer


  • Ultra-Low noise low leakage mains transformer produced in-house for 230Vac (115Vac via jumper setting). 100Vac (Japan), 120Vac (USA, Canada), 220Vac (South Korea, China, Thailand, Indonesia), 240Vac (UK) or 245 Vac (Australia)

  • Full hand construction, point-to-point wiring throughout

  • Non-magnetic case (aluminum throughout

    • Anodized printing on front and rear panel

    • Powder-coated chassis and lids


  • Dimensions - mm : 

    • 150 W x 595 D x 330 H 

    • H / 330mm = 20mm (feet) + 210mm + 100mm (tubes over case)

    • D / 595mm = 575mm + 20mm (speaker binding posts)

    • Dimensions of the shipping crate - mm:

    • 950 D x 400 W x 460 H

    • Shipping weight : 14Kg each



Individually Made in Germany

MSRP   $ 12,000

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Show & User-System Coverage

Please Listen with Quality Headphones at Youtube Hi Res Settings

For Thoeress : Listen as of 2:22 minutes

What the say ...


Wojciech Pacuła |  Sep 1, 2023  

The SE300B is THÖRESS' latest product. It's a single-ended, triode (SET) power amplifier based on the 300B tube, a direct heated triode. In this circuit, it guarantees 10 watts of output power (which is quite a lot), although the manufacturer does not specify at what distortion. In general, we won't learn much about how this device measures.


The output tube is the most important element that distinguishes this amplifier from the 845 Mono. The appearance of the device, the layout of the components inside, the transformers, and finally the input layout, are very similar. The device was conceived as a "functional machine". It takes the form of a long, rather tall, though narrow cuboid facing forward with a narrow wall. The sides are painted in a distinctive dark green color referring to the color scheme of the mid-20th century.



I am talking about „function” for a reason. If you have a moment to close your eyes, please do, and imagine that the amplifier is facing the side towards us. What do you see? In my case, it's a slightly modified version of QUAD's iconic amplifier, the 'II' model, and to some extent the McIntosh MC275. Now imagine the back of the SE300B up front. What has just appeared on the screens of our eyelids? - Well, I assume, a device similar to the Kondo OnGaku, only with the input on the front instead of the side.


This layout of inputs, outputs, transformers and amplification elements is intentional. When perfectionist audio was born, the biggest issue was significant hum, and one of its sources was the proximity of these sections. Before we get to that, let's say that it's not the only one. The issue in amplifiers with 300B in the output was that the heater voltage (5 V) was an AC voltage, and the filament and anode in it are powered from the same point. This problem is solved by rectifying the supply voltage, but you also need to determine it precisely - this is what the "Symmetry" knob is used for in the tested amplifier. It is not a perfect solution, which we will discuss at another time, but we get low hum thanks to it.


The second way to reduce interference from the power supply is to physically separate the input and output tubes, and the transformers from all of them. And that's why the German amplifier looks the way it does. The line inputs and input tubes are placed in it at the back, far from the power section. Nota bene - the tubes are the magnificent CV2382/EL822 (V2382KB/QDD) NOS-type power pentodes, somewhat similar to the EL84, operating here in a triode arrangement. This section was designed for earlier equipment from this company including the - mentioned - 845 Mono model.


From the CV2382 tubes, the signal runs forward to the slightly distant end tube. It's underneath it, slightly in front, that the large output transformer, with classic EI plates, was located. It's far enough away from both the 300B and the input that it doesn't interfere with them, and close enough to the output tube that the connections between them are short. The signal to the speakers has a high level, so it is less susceptible to interference. The output terminals are single, but you can adjust the output impedance for your own speakers - just solder (or order soldered) outputs on the transformer.


So when I heard how the Thöress monoblocks played John Coltrane's Crescent I already knew what to expect. And they played it beautifully, oh - how beautifully!  Soft, resolving, warm, dense, in an open way - all at once.


There was not a hint of mechanics in this presentation, as if the amplifiers were transforming the signal to convey every detail as accurately as possible, but as it was played, not recorded. It's a sort of "leap" over the entire recording and playback process directly to the moment when the music and sound were born.

That's why the leader's saxophone was so compellingly "present," and ERIC DOLPHY's baritone saxophone, played immediately afterwards in God Bless The Child, had an incredibly natural descent and was big, present, tangible.


I played both tracks from an SACD prepared by Shoji "Swifty" Sugawara, a hugely important figure for Japanese jazz, whose club Count Basie once played in, and where you can listen to music every day through a top-of-the-line, vintage JBL system. He has impeccable taste, as demonstrated by this very two-disc album. Nowhere else would tracks as disparate as the previous two, and the Louis Armstrong's live recording "On The Sunny Side Of The Street", recorded in 1947 and "copied" from slightly crackling acetal, would sound so coherent.


The special feature of the Thöress amplifier is -- right after the aforementioned ability to get to the heart of the music being played -- a very rarely experienced energy transfer. When a sound wave reaches the microphone diaphragm, most of its energy is converted into current, but some is irretrievably lost. The same happens at every stage of recording and later playback. The extinct elements of the original sound are usually low-level signals, responsible for whether or not the presentation is believable, for phase shifts, soundstage, etc.


And that's where the amps truly shine. Because it seems as if all those details that came to them are reproduced without any modifications. That's why the sound is so remarkably natural and tangible. The device differentiates recordings, that's clear. 


The HARRY JAMES' explosive Caribiribin - Trumpet Blues ... and COUNT BASIE's Jumpin' At The Woodside, that we played immediately afterward, sounded completely different ... The former, open at the top of the band, accurate, with precise attack and very well captured dynamics ... while the latter, at one dynamic level and with limited frequency response.


What they had in common was the saturation of the midrange, the fantastic shaping of the sound attack and the ability to sustain it in such a way that everything came together, was "sticky" in a way. At the same time, this viscosity describes the timbre, not the dynamics, because the latter was above average, but without falling into hyper-literality. Thus, if one were to describe the timbre of this device in isolation from other features one would have to say that it is warm. Those of you looking for aggressiveness in the sound will not be thrilled.


But those looking for energy in this presentation will find more than enough of it. Even in the rather compressed, slightly rumbling Pozwól mi być z tobą tu by TADEUSZ NALEPA. Positioned by the producer in the right channel, the two electric guitars are not far apart - the rhythm guitar a little further to the right, and the solo leader a little closer to the center. But they're close enough to each other that it's easy to fuse them into one sound. And Thöress distinguished them not only timbrally, but also rhythmically. There was no doubt that they have a different place on stage, emphasized, moreover, by the longer reverb on Nalepa's guitar.


I loved it how it came out in the intro to the Ego Death track by PYLYPHIA, featuring Steve Vai on guitar. Just as before in Nalepa's song, the sound was big, had a strong punch and very, really good bass. The thing with 300B tubes is debatable, because to generate low, well-controlled bass, after all, you need a lot of current, and not many designers know how to ensure such capability. Here there were no major problems with it, except perhaps at the lowest end of the band.


The low tones are generated strongly, unambiguously by the SE300B, with great dynamics and no audible distortion. Even with speakers as difficult to control as the Harbeth 40.1. As I've written several times before, many, even powerful amplifiers don't handle them very well. But all it takes is an amplifier with a stable power supply and high peak current capabilities for them to "sing". And it doesn't matter whether it's a 100-watt transistor or a 10-watt tube, as in this case. The only difference is in the maximum sound pressure level (SPL) they manage to generate. In my case, at a distance of two meters from the speakers, it didn't matter much.


Even with such difficult material as the BBY track by TWO FEET : Difficult, because it has a very low, electronically generated bass, playing with the phase on the guitar and vocals, with a motoric tempo, etc.


None of the aforementioned elements can be weaker than the other, because if just one does momentarily get weaker, everything "falls apart". The amplifier from Aachen showed all this effortlessly. It played a very big sound with strong and low bass. The latter is not super-selective, it's not that type, but it keeps everything in check by controlling the rhythm.


And perhaps all this does not matter? Because it may happen that it is listened to by someone who doesn't know it ... doesn't want to know it ... and doesn’t give a s...t ... Good ! ...


... because -- for someone like that -- the most important thing will be that Thöress will play almost any music as if it were at that moment the most important thing in its life.


Whether it's effing jazz classics, or music born in the guts of a computer, or even older pieces that usually sound light and "thin," like Magic Fly by SPACE ...

You know this track, even if you don't realize it at the moment - but you haven't heard it yet in a way that Thöress presents it !!




The Sound of the tested amplifier is super-pure. I didn't mention it in the test, because it's a basic thing, it's what everything comes from, but which, it seems to me, is often misinterpreted. Purity in this case is the absence of coloration, but not only that no coloration is added, but also that nothing is „deducted”. Purity only with the former kills the music, and that is bad purity.


Thöress plays everything with graceful, effortless ease. And although in dense recordings like AURORA's Home, from her excellent album All My Demons Greeting Me As A Fiend, when I cranked up as much as I could, the sound was slightly overdriven, I was way out of my comfort zone at the time. At normal volume in conditions such as those in the High Fidelity listening room, you can play music loudly and it will be full scale, clean, immersive and extremely dynamic. It is truly a beautiful sound.


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