MM-PH-AMP –
Pure MM Phono Preamplifier

Our Goal: Absolute Phase Linearity

The temporally correct reproduction of all frequencies in the audible range determines whether a record is perceived as vivid, natural, dynamic, finely resolved, spatial and simply genuine. If this is the case, we don’t just listen to the music, we feel it, it carries us away emotionally.

This is why we have made phase linearity our top priority in the development of our MM-PH-AMP and have consistently and uncompromisingly subordinated our design measures to this goal.

Achieving a clean frequency response from 20 Hz to 20 kHz is no great feat. However, in order to realize a linear phase response in this range, five octaves of headroom are required. This means that a time-correct reproduction at 20 kHz requires a linear frequency response up to 640 kHz. The MM-PH-AMP can even work up to 800 kHz or 1 MHz, depending on the selected amplification. The same applies to low frequencies; the lower cut-off frequency is 3.2 Hz and we have deliberately dispensed with a subsonic filter.

RIAA equalization not only restores the frequency response, but also linearizes the phase response. With single-stage MM amplifiers, the necessarily high gain of + 40 dB narrows the upper frequency response, which also affects the phase response in the audible range. A passive RIAA equalizer takes care of this in the MM-PH-AMP. High-quality, double-sided coated MKP capacitors ensure that the losses of the passive equalization are limited purely to the calculated high-frequency attenuation (approx. 20 dB). The result: linear frequency response and linear phase response up to over 20 kHz. The two amplifier stages upstream and downstream of the equalization operate at only +30 dB gain each and are so broadband that the phase response remains linear.

This design was previously reserved for tube amplifiers only. We have succeeded in transferring this classic concept to modern amplifier electronics. The result: no cold and analytical sound as with transistors, no bland and flat impression of the music as with previous OPs and a significantly lower distortion factor than with tube amplifiers.

Some other very effective measures in the power supply and voltage stabilization reduce interference and hum, enabling us to achieve a signal-to-noise ratio of over 90 decibels.

The Sonic Goal: Music

Pure music flows through the veins of the MM-PH-AMP. The phono preamplifier—like our SUT-1M and SUT-1L transformers—should allow the artists to penetrate us holistically and directly and not play itself into the foreground in any “discipline”.

The phono preamplifier transports all the nuances of a vinyl recording. But without gimmickry, but completely naturally and confidently. With all the macrodynamic attack and microdynamic accents that go with it.

You are not listening to the MM-PH-AMP, you are listening to music with it!

Technical Design And Special Features

• Dual-mono construction
• A small number of extremely high-quality and carefully selected components: We tested their interaction in intensive listening sessions and ultimately combined exactly the components that met our high standards.
• Passive RIAA equalization with ultra-fast MKP film capacitors coated on both sides: this means maximum resolution and dynamics
• High-quality OP amplifiers with very high speed (150 V/µs) and bandwidth. The MM-PH-AMP achieves an upper cut-off frequency of up to 1 MHz and a linear phase response up to 31 kHz.
• Powerful Class A power amplifier at the output, which could even drive loudspeakers (if cooled accordingly). This means that longer cables from the MM-PH-AMP to the preamplifier are completely unproblematic. The output resistance was set to 22 ohms to avoid short circuits.
• Common filtering for both channels for maximum homogeneity of the channels. This takes place partly in the external power supply unit and on the shared mainboard. The total capacitance of two times 23,500 µF is filtered step by step over 4 stages. This purely passive (!) circuit is also an inrush current limiter. This means that the toroidal transformer can be protected with a lower fuse value, thus avoiding typical switch-on problems of such transformers.
• Separate voltage regulation for each amplifier stage, with a high degree of attenuation as close as possible to the load – thus minimising interference and maximising dynamics
• Channel-separated adjustment of gain, capacitance and impedance very close to the amplifier modules. This shortens signal paths and minimises interference.

Controls And Settings

With the MM-PH-AMP, you should be able to concentrate fully on the music. We have placed all potentially distracting controls on the rear panel.

There are no mouse pianos, but solid rotary switches with clear labelling and intuitive operation:

• 3 gain stages (We recommend 46 dB for transformer operation.)
• 4 input impedances
• 4 capacitances (in transformer mode, we recommend 150 pF or 250 pF—depending on the cable length)

PSU MM-PH-AMP Power Supply

To eliminate potential interference and interactions, we have outsourced the power supply unit of our MM-PH-AMP. The connecting cable measures 1.2 metres. Long enough to cover the distance between the power source and the amplifier.

When the power supply unit is switched on, a small 2 VA power supply unit supplies a switching voltage, which activates a relay in the PSU via the switch on the MM-PH-AMP and only then switches the toroidal transformer through.

The fuse compartment also has a spare fuse (200 mA T, ceramic).

In view of the low power consumption of only 8 watts, we recommend operating the MM-PH-AMP “always on”.

Technical data and details, price

Cabling

We are offering phono cabling in all variations and with best price-performance ratio. Thanks to numerous listening sessions and cable comparisons, we decided on a cable whose material, winding and shielding concept are predestined for high-end phono reproduction.

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