Amplifier DM 250

The harmonics and phase conversion system changes the proportions in the spectrum of harmonic distortion!

A world of music from the comfort of your own home!




“Mr Zdzisław was able to achieve the incredible amplifier – it is beautifully intense, dense, but it does not blend everything into gruel. Its trebles, have exceptional ease in filling the bandwidth without brightening or sibilants. The bass is majestically profound and powerful, although it does not compete with the best with it’s control and selectivity. It creates just a good background and a foundation”.
Amplifier test on High Fidelity
Wojciech Pacuła, July 2018.


Struss dual mono amplifier has been equipped with a PRE IN switch which means our device can act as a preamplifier and enables independent use of internal power amplifiers.

Amplifier modes: Phono, XLR, CD / DAC, AUX1 (universal), AUX2 (universal), PRE IN


After many years of trials and improvements, a design was developed whose spatial layout of individual electronic and mechanical elements allowed to obtain the shortest possible connections between elements, high resistance to interference with an excellent cooling system and thermal stability.

One of the unique design solutions used in DM250 is the HPCS (Harmonics and Phase Conversion System). It is constructed on the basis of a transistor (J-FET) system, in which thanks to precisely selected technical elements, it was possible to obtain the effect of generating even harmonics, whilst reversing the phase of the signal. The HPCS system is a solution that, introducing some subtle modifications in the spectrum and dynamics of the acoustic signal, adapts the sound of the DM250 amplifier to the subjective needs and characteristics of human hearing. This resembles to a certain extent, the effects obtained in tube amplifiers, but without the inconvenience of using lamps. In addition, the amplifier has the ability to precisely amplify the acoustic signal throughout the whole acoustic spectrum, with a perfectly sounding and dynamic low frequency range. Also, the enhancement of medium and high frequencies, with a negligible effect on phase shifts, allows the listener to hear the exact location of apparent sound sources and the effect of reproducing sound and depth plans of the sound image. Thanks to this, it is also possible to obtain the effect of a “holographic sound field” that goes far beyond the classical effects of stereophony.
DM 250 has extremely vivid and colorful sound, whose values have been very highly rated by specialists from the professional sound and sound system industry, as well as lovers of high quality audio systems.

The amplifier has a phono input for the MM cartridge, anda RIAA correction preamplifier in which the Texas Instruments integrated circuit is used, based on the JFET structure.
The RIAA curve was modified, adding an additional time constant of 3.2 uS (Neumann), thus obtaining a greater spatiality of the musical image.
The power amplifier is built as a dual mono circuit based on FET transistors. The entire signal path was designed in such a way that the user could use two parts separately, i.e. from a preamplifier or power amplifier. The disconnection of these two components takes place by means of a switch placed on the front panel. In addition, there is the possibility to directly connect the power amplifiers to the acoustic signal source.

Combination of power amplifiers with high quality sources of signal, creates extremely precise and transparent image of audio scene with accurate and detailed reproduction of tiniest sound details. The DM250 amplifier allows you to transport the listener to the real acoustic space of the music being listened to.


Power:8 Ω / 2 x 130 W (CLASS AB)
4 Ω / 2 x 250 W (CLASS AB)

Minimum impedance load: 1 Ω (instantaneous)

Work in class A up to: 2 x 10 W

Power consumption: STATIC 40 VA – 800 VA (PEAK)

Output impedance: 0.10 Ω

Distortion – THD:
0.1% at 1 W / 8 Ω,
0.025% at 130 W / 8 Ω

Frequency response: 5 Hz – 250 kHz – 3 dB / 1 W / 8 Ω, 10 – 30,000 Hz: ± 0.1 dB

Slew rate: 200 V/μs

Dynamics: 140 dB

Signal – noise ratio: 145 dB (IHF – A)

2 x universal – RCA
XLR Amphenol
separated CD / DAC – RCA
phono MM – RCA
input power amplifiers – RCA

Preamplifier: output – RCA

Sensitivity of inputs:
500 mV – universal inputs and dedicated CD / DAC
250 mV – XLR input
3 mV – MM input
0.775 V – power amplifiers

Impedance inputs:
100 kΩ; universal inputs and CD / DAC
22 kΩ XLR
47 kΩ MM
47 kΩ power amplifiers

Potentiometer (volume): the highest precision model the Alps – Blue Velvet

Transformers: 2 x toroidal, magnetically isolated 500 VA each

Capacitors filtering the supply voltage: 4 x 15 000 uF – Nippon Chemi-Con

Advanced protection system: against short-circuiting of the loudspeakers and a stream of DC voltage at the output

Remote control:
RC5 code (volume)
The DM 250 amplifier fulfills all requirements and standards valid in the EU

Net weight: 16 kg
Dimensions: 430 x 102 x 338 mm
Manufacturer’s warranty: 24 months


Remote Control: code RC5 (volume)


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