What is: 4CH Architecture

[Jelle Schrijver]

Hi there,

I understood the 3ch Architecture, but what is the deal about that 4th one?

isolating the amp from the buffer on the ground channel or is something else going on?

Anybody out there who is willing to share the secret?

[m3_arun]

As far as I know 4 ch = fully balanced configuration. It means that each channel is driven by one signal on the + terminal AND an inverted-phase signal on the - terminal. So there is no real ground anymore, just a "floating ground" which is the sum of both + and - signals.

[Ricey20]

isnt thrice's B22 6 channel or something? How does that one work?

[Duggeh]

4 channel balanced and active ground depending on if you use an xlr or trs socket?

[m3_arun]

The β22 Stereo Amplifier If you click on "other options" and go to the bottom you can see how the 6-channel is set up. Basically only 4 boards are actually used to drive a pair of balanced headphones. The extra two boards provide active grounds for TWO pairs of unbalanced headphones. So for single ended headphones its like two full amplifiers in one box. If you only needed one single ended headphone output, looks like you could go with 5 boards instead of 6.

[Jelle Schrijver]

Originally Posted by m3_arun

As far as I know 4 ch = fully balanced configuration. It means that each channel is driven by one signal on the + terminal AND an inverted-phase signal on the - terminal. So there is no real ground anymore, just a "floating ground" which is the sum of both + and - signals.

Thought of that, but it would not work with a trs connector, the headphone shares it groundsignal in that manner . Also i am not sure if you put the 2 amps that are busy making a negative signal together, would one not short out the other?

[majkel]

In unbalanced amp it would be:
- left channel amplification
- right channel amplification
- active virtual ground
- headphone ground channel, independent from the active ground for input and NFB loops.

[xxlMusikfreak]

Thought of that, but it would not work with a trs connector, the headphone shares it groundsignal in that manner . Also i am not sure if you put the 2 amps that are busy making a negative signal together, would one not short out the other?

If you use your headphones balanced you have to use two trs/XLR connectors (or one with 4 connections) - one for each side. The headphones must be recabled or at least receive a new plug (if it already has a 4 wire cable) to use it in balanced operation. You can't use a normal trs plug for balanced operation.
Either 2 trs/XLR plugs from one headphone (with only 2 wires connected to each driver - the 3. ground connection of the trs/XLR is not connected to the phones) or 2 SE phones connected to the two trs/XLR-jacks (with normal ground this would be a 4-channel design with balanced ground for both it would be a 6-channel design).

[Jelle Schrijver]

Originally Posted by majkel

In unbalanced amp it would be:
- left channel amplification
- right channel amplification
- active virtual ground
- headphone ground channel, independent from the active ground for input and NFB loops.

Thanks! I suspected something like that.

About balanced amps, in the experience by using 2 amp channels to drive a speaker, i found that it hurts the rhythm and pace. So i am not a big fan of this kind of setup. Guess it has something to do with very minute differences in component values and creating some ultra micro time smear effects.

[m3_arun]

Originally Posted by majkel

In unbalanced amp it would be:
- left channel amplification
- right channel amplification
- active virtual ground
- headphone ground channel, independent from the active ground for input and NFB loops.

I don't understand this, what is "active virtual ground" hooked up to?