Friday, October 11, 2013

Mono blocking or Bi-Amping

Monoblocking or Bi-Amping?

There are three ways to let the two channels of a stereo amplifier work together to drive a single loudspeaker.

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 good solution.

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!


Joost Plugge

DaDa Electronics