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Ultimate 3 Channel B22 w/ Triple Mono PSU?

beta22

Ultimate 3 Channel B22 w/ Triple Mono PSU?

Postby deltaunit » June 1st, 2011, 9:43 am

Hello AMBiers,

I've very recently come across the B22 headphone amplifier and am currently in the exciting phase of researching a new project. The b22 looks fantastic 8-)

I was interested in building an ultimate two channel dual psu headphone amplifier but after reading about the clever 3 channel active ground B22, I'm now thinking about building a 3 channel version with a triple mono psu and I wondered if this was a) a stupid idea or b) a good idea and wether it was even possible with 3x S11 boards or 1x S22 & 1x S11 boards.

If I were to build a dual channel amp, would there be any significant differences between running 2x S11 and 1x S22 PSUs? Is the S11 compatible - would it work?

Many thanks
Last edited by deltaunit on June 1st, 2011, 1:19 pm, edited 1 time in total.
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Re: Ultimate 3 Channel B22 w/ Triple Mono PSU?

Postby amb » June 1st, 2011, 1:19 pm

I don't recommend triple PSUs for a 3-channel active-ground configuration, because you would lose the supply rail current cancellation benefit that a single PSU with 3-channels would give you.

Also, the β22 cannot be powered with the σ11 PSU no matter what the configuration is. It needs a dual-rail (positive and negative) supply, but the σ11 is single-rail only. You could build a dual-rail supply by connecting two σ11s in series, but why do that when there is the σ22?
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Re: Ultimate 3 Channel B22 w/ Triple Mono PSU?

Postby deltaunit » June 3rd, 2011, 3:02 am

:oops: Oh yes, thanks for your response. With a little more reading I can see that the S11 isn't 'basically' the same as the S22 as I first thought!

Is the single regulated PSU beneficial in a 3 channel setup because the active ground requires a shared reference and that variances with 3 independent power supplies would result in increased crosstalk? I'm not sure I totally understand why mono PSUs aren't beneficial.

At least with a single PSU the costs will be less and case smaller :)
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Re: Ultimate 3 Channel B22 w/ Triple Mono PSU?

Postby amb » June 3rd, 2011, 1:36 pm

deltaunit wrote::oops: Oh yes, thanks for your response. With a little more reading I can see that the S11 isn't 'basically' the same as the S22 as I first thought!

The σ11 is exactly half the σ22, the former has only one output rail rather than the latter's tracking positive/negative output rails.

Is the single regulated PSU beneficial in a 3 channel setup because the active ground requires a shared reference and that variances with 3 independent power supplies would result in increased crosstalk? I'm not sure I totally understand why mono PSUs aren't beneficial.

In a 3-channel active ground topology, the ground channel sources and sinks the return currents from the left and right channel headphone transducers and routes that summed current into the supply rails rather than to signal ground. When operating in class A, that return current being routed back to the rails by the ground channel amp is exactly equal but opposite in phase as the sum of the currents being drawn by the left and right channel amps, thus a rail current cancellation occurs. The supply rails become totally quiescent, and does not "bounce" with the signal as might be the case with a conventional 2-channel amp. The signal ground is also not affected by the return currents because they do not go there. Of course, in order for rail current cancellation to occur all three channels must share the same rails.
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Re: Ultimate 3 Channel B22 w/ Triple Mono PSU?

Postby deltaunit » June 6th, 2011, 1:22 pm

Thanks AMB, that was very helpful. I look forward to building a single psu 3 channel amp later in the year. Cheers
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