GamuT M250i - Manual (Page 6)

Connecting your loudspeakers
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.
Biwiring: This also gives you the ability to connect biwiring nicely, using the filter output for the
bass and the direct output for the treble. However, you will achieve the best possible sound and
the most correct tonal balance when biwiring both bass and treble from the same pair of output
terminals, choosing either direct or normal.
NB: When biwiring an electrostatic loudspeaker, please connect both cables to the normal
(filter) output.
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.
The red terminals go positive when there is a positive signal on the Pin 2 on the input XLR.
In other words, GamuT amplifiers are non-inverting. Some other brands of amplifiers do not follow
this standard. Keep this in mind if you want to bi-amp, with another amplifier from another brand.
Loudspeaker impedance
Most loudspeaker are 8 or 4 Ohm, and they are specified so by the manufacturer.
Unfortunately, some loudspeakers have an impedance, which is much lower than specified.
They will not damage the GamuT power amplifier, because it will simply mute.
In the GamuT M250i, we use a gem of a MOSFET transistor. It handles 500 Watts, and a peak
current of 400 Ampere and 100 Ampere long-term.
Such high currents will destroy any HiFi loudspeaker we know of.
The lower the impedance, the higher the current will be.
Somewhere, we have to draw a line between what is a loudspeaker load, and what is a short circuit.
We have set this line at 1.5 Ohm, which will draw about 47 Ampere peak.
The impedance of a few electrostatic loudspeakers does go down below 1.5 Ohm at high
frequencies. The protection circuit will not allow this longterm on test signals. However, it works
well with Quad ELS-63 and most Martin Logan electrostatic loudspeakers.
Please also note that a Quad ELS-63 electrostatic loudspeaker cannot handle more than 55V peak,
and the GamuT can give more than 70V peak. So be careful.