There are three ways
to let the two channels of a stereo amplifier work together to drive a single
First there is the
serial monoblock. The speaker is connected between the two ‘hot’ outputs and
the inputs are driven in anti-phase. The output part is simple, but for the
input you will need a separate circuit or a special input transformer. The
disadvantage of this way of monoblocking is as follows; it will deliver more
power, but in higher impedances. So for modern low ohmic speakers this is not a
The second way is the
so called parallel monoblock. On the output side you need resistors to function
as a current sharing circuit. On the input you need a potmeter to make the
output voltages of the two channels equal before the current sharing resistors.
Now the combined amplifier deliver more current, this is a big advantage for
modern speakers. The amplifier clipping point is at higher volumes and the
distortion will be lower at the same volume level.
The third technique
can only be applied if your loudspeaker
has a separate input for the treble and woofer section, it is called Bi-Amping.
It is very simple, remove the wire or strip of the speaker terminals and
connect the two amplifier channels with separate cables to the speaker inputs.
On the input you need a special cable or coupler to split the signal coming
from one channel the pre amplifier and connect it to both the inputs of the
power amplifiers. In this way you have applied so called vertical Bi-Amping.
There is also a variant called horizontal Bi-Amping and is necessary if the two
stereo amplifiers are of different power rating. The vertical Bi-Amping shares
the advantages of the parallel monoblock because the single amplifier channels
will ‘see’ a higher impedance.
The big advantage of
Bi-Amping; no work have to be done inside the amplifiers!
Comment on the picture, a Bi-Amping setup with a high WAF factor!