Gamut M250 User Manual - Page 4

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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 Brass logopanel is covered with a protective layer.

DO NOT USE ANY BRASS POLISH. This will remove the protective layer.

The protection circuitry

The ideas for the protection circuit come 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 long-term overload.

The protection detects DC errors, high level subsonic signals, long-term ultrasonic signals, high tem-

perature, 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.

Connecting your loudspeakers to the output terminals

Normal power amplifiers have a coil in parallel with a resistor between the amplifier and the output

connector. Its purpose is to protect the amplifier against capacitive speaker and cable loads. However,

this will slightly reduce the fidelity of the sound in the treble range, when the amplifier is used with normal

loudspeakers. So we have added a direct output in addition to the normal filter protected output.

The red terminal closest to the heat sinks is the direct output. The other red terminal is the filter output.

The white terminals are ground

This also gives you the ability to connect biwiring nicely, using the filter output for the bass. and the di-

rect output for the treble

In case of biwiring an electrostatic loudspeaker, the reverse should be done.

Inside the cabinet the ground terminals are kept biwired until they meet at the main star ground point.

So please do not connect them together.