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


Blogger Unknown said...

Hi Steefan,

I have the Quad Elite, Cdp + Pre + 2xStereo Amps + 23L speakers.
According to the manual, if you use the 2 amps using the quadlink cable, the system configures itself to separate High and Lows before the amp.
I dont know the technical details but it sounds much better with de 2 amps, even at low volume. More definition & less distortion.


1:51 PM  
Anonymous Fabian said...

Wow, not only the WAF is high, I would think. Very lean and neat and slick and elegant setup. Very nice.

What arm and pickup cartridge are you using (I'm not exactly a Garrad specialist).

One last question remains to be answered: what multi-amp setup are YOU running? I will try to guess. You are running two 606, which are super powerful already. Your Martin Logan speakers look like a pair of Theos, which do have bi-amping terminals. In conclusion, my guess is, you are running a bi-amping setup. Right?

Don't you hear some occasional twitter from the right channel? ;-)

10:47 PM  
Blogger Stefaan said...


Thanks for the nice comments. I use the 606's in so called vertical Bi-Amp mode. So each 606 is driving a speaker (ML Theos indeed). The Quad Elite bus forces you to use the horizontal Bi-Amping, no problem. The arm on the Garrard is a 12" Jelco, the cartridge is a Stanton, untill something betters arive.

Joost Plugge

1:19 PM  
Anonymous Phil said...

When configuring two power amps in the bi-amp configuration you mention a special cable is needed can you say exactly what is needed and if it is a cable you suply

2:18 AM  
Blogger Stefaan said...

You need a cable with one RCA connector on one end and two RCA connectors on the other end, we don't stock those, but we can custom made this cables. Send a mail to Stefaan in Antwerp.

Best regards

Joost Plugge

1:07 PM  
Anonymous Stuart Adamson said...

I use a pair of paralled 606s to drive a pair of ESL63s. I find that the 63s no go unpleasantly loud but I have yet to have the protection circuit operate and I think this is because the amps do not clip


10:42 AM  

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