I'm thinking about a β22 build for dual-duty headphone and speaker use. A while back I was looking at a much bigger balanced setup for bigger speakers, but I've scaled down my speakers recently and want to scale down this build as well. I'll replace my current M^3 + Gainclone setup with this.
I'm planning on a two-board build with one σ22 per channel. The speakers will be these or something similar for nearfield use. The set I linked has drivers rated at 86.5dB/W(m). Yes, it's a little sad to be reduced to 3" drivers, but such is my life. I'll add a line out to the build so I can support a subwoofer too.
I'm trying to fit everything into a smaller chassis, roughly 8"x8"x3". I had thought I could power both β22 boards with a single σ22, allowing me to also fit the transformer in the σ22 case, but doing some rough thermal calculations for onboard heatsinks it seems the σ22 would be a significant bottleneck. To address that, I'll move the transformer to its own case and stash it somewhere with a long-ish connecting cord. At least that'll keep any interference far from the amp.
My questions:
1) Using 2" onboard heatsinks and a shared transformer for the σ22s, with +/- 27V output, I'm thinking a model around 200VA seems right. Avel Lindberg has a 230VA unit with 25V secondaries. Is that overkill?
2) The transformer chassis should be connected to AC ground, the β22 chassis should be connected to input ground, but how should I ground the σ22 chassis in this configuration?
3) Should the ground wire for the speaker binding posts return to that channel's respective σ22 ground terminal? For the headphone jack, I imagine I can just pick one of the σ22 ground return wires?
4) Is a gain of 8x suitable, or is a gain of 11x preferable? The source will be my y2.
Thanks!