SINCOS MonoAmp Mk3

A PWM amplifier based on the principle of the internationally patented sine-cosine modulator impresses with extreme detail resolution and neutrality, making the power amplifier practically inaudible in the signal path. This "inaudibility" was only achieved through significant effort in voltage stabilization, meaning earlier versions did not yet reach their full potential. In the Mk3 version, each MonoAmp has at least two separate power supplies: an unregulated and oversized power supply with a 400VA toroidal transformer and 54mF charging capacity solely for the power transistors, which draw current in sync with the rhythm of the music, and a regulated control power supply with a 30VA toroidal transformer for all other electronics with more or less constant current consumption. The issue lies in the "more or less".

Theoretically, a sine-cosine modulator is the ideal power amplifier, but in practice only with perfect supply voltages, of which four different ones are required: +44V for the MOS power switch stage, +10V for the MOSFET drivers, and symmetrical +5V and -5V for the PWM modulator that modulates the music signal onto a 460kHz carrier frequency. At this high frequency, the power supply rejection ratio (PSRR) of even the best available operational amplifiers drops below 60dB, meaning the resulting sound quality depends on how well the +5V and -5V are stabilized. Even small supply voltage fluctuations resulting from minor changes in current flow can be heard as impurities in the sound. Additionally, the three operational amplifiers and especially the two comparators that form the PWM modulator generate high-frequency oscillations up to the 100MHz range, causing interference with each other via the shared power supply. These problems remained unresolved in all previous PWM amplifiers, which is why they remained in the middle of the audio spectrum.

In the SINCOS MonoAmps Mk3, two symmetrical and twelve asymmetrical high-frequency filters, along with 1 x LT3081, 3 x LT3045, 1 x LT3094, and 10 x LM4040-5, are used for voltage stabilization, ensuring that each operational amplifier and comparator in the PWM modulator, as well as the MOS drivers, are individually stabilized and decoupled from each other by HF filters. The entire stabilization chain, which only uses ceramic multilayer capacitors with the best high-frequency behavior and highest stability, was optimized down to the last detail over three years and through hundreds of listening tests to unlock the full potential of the sine-cosine modulator. The sonic result is described by Dr. Martin Mertens in HiFi Test magazine (issue 3/23), which had the opportunity to test the first Mk3 prototype, as follows:

"I am almost certain that many experienced listeners would initially believe that the SINCOS MonoAmps are excellent tube amplifiers. This is primarily due to their phenomenally finely resolved mids. What these Class-D amplifiers deliver here is among the best available, regardless of price range. The amplifiers have an extremely high resolution, while the entire presentation feels completely free of artifacts or harshness. Vocals are delivered with impressive expression. Every nuance of vocal modulation is cleanly brought out by the SINCOS MonoAmps, without ever sounding technical or analytical. The same applies to the reproduction of instruments, which the SINCOS MonoAmps render down to the finest details, always sounding authentically natural.
    The bass range could also be sonically assigned to an excellent tube amplifier. It impresses less with absolute hardness and ultimate (forced) control, but instead brings deep tones with substance and a captivating swing. This is exactly right for all acoustic instruments. It feels as if the speakers with the SINCOS MonoAmps reproduce basses half an octave lower than comparable Class-AB transistor amplifiers. ...
    Originally developed for our own active speakers, the amplifier modules in the full-range version are also perfectly suited for driving passive speakers of any kind. They offer the advantages of Class-D, such as high efficiency, low power consumption, and hardly any heat generation, with a sound that many high-end amplifiers of the AB or tube faction must measure themselves against."

The SINCOS MonoAmps Mk3 can be retrofitted with additional amplifiers, up to four separate power supplies, and a corresponding phase-parallel analog active crossover to drive one of our new active systems, such as the MS6EH Mk3, MS8EH Mk3, FS62E Mk3, FS82E Mk3, or FS82Be Mk3. The full purchase price of the broadband version will be credited towards the purchase price of the respective active system.