Michell GyroOrbe Pabst AC Motor Power Supply

[User211]

So we're in floating bridge-tied load (BTL) TPA3255 mode here. But we always were. Both Gemini and Grok did't really get it.

Eventually I got Grok to fess up. Here's the transcript.

Grok:

"BTL stands for Bridge-Tied Load.
It means the speaker (or motor winding) is connected between the two amplified outputs of a channel (Out+ and Out−) rather than between one output and ground. This doubles the voltage swing across the load compared with a single-ended arrangement and is the normal operating mode of the TPA3255 in stereo."

Me:

"But we did not see that voltage doubling, Grok."

Grok:

"You’re right — we didn’t see any voltage doubling.

That was my earlier mistake. In both of your configurations each motor winding was already connected across the full differential of a BTL channel, so the amplitude stayed essentially the same. The higher PGA value you needed was due to polarity / capacitor placement differences, not a sudden doubling of voltage.

Thanks for keeping me honest on that."

Hm.