GamuT M250i - Manual (Page 5)

Cleaning the cabinet
The front panel is made of aluminium. It can be cleaned by using normal mild solvents and clean
paper tissue or cloth. Do not use excessive amounts of solvents, and do not let any of the solvent
spill into the amplifier.
The protection circuitry
The ideas for the protection circuit comes from our professional amplifiers, where it has worked
well since 1982. Due to the rugged MOSFET, we can allow high peak currents , and we only need
to mute the input signal in case of longterm overload.
The protection detects DC errors, high level subsonic signals, long-term ultrasonic signals, high
temperature, and to low impedance loads or short circuits.
If needed, the protection will simply mute the input signal, and if necessary open the output relay.
The relay will normally open only after muting the input signal to avoid relay switching of strong
currents that could corrode the relay contacts.
So in case of i.e. a short circuit the input is muted for a second. Then a 1 millisecond long pulse is
sent out to test again. If the short circuit still is present, it waits a second and tries again, and so on.
One second after the user has removed the faulty cable, the system will quickly remove the muting.
The protection also detects too low impedance loads, and alerts the user by muting for a second.
So the user can be sure to hear only clean non-distorted audio. The normal current limiting and
momentary distortions of the music are avoided in the GamuT M250 power amplifier.
A second of silence
You may experience a second of silence while the music is playing loudly. This is the protection
acting to protect your tweeters. Any amplifier will start to clip the top of the music if you exceed
the maximum power level. Technically, clipping generates a lot of high frequency energy, which
can burn out the tweeters in your loudspeakers. The protection constantly checks the energy
above 20 kHz, which humans do not hear. The distortion is momentarily very high anyway,
because you have exceeded the maximum power, so just reduce the level a bit.
You can also provoke the subsonic protection by playing warped records without using a
subsonic filter. Please check your tonearm/cartridge resonance frequency, which should be about
8-12 Hz to reduce the effect of warped records.