Small audio transformers for isolation and impedance matching

[Helmholtz]

It is weird that the designer tied the grids together eh?

I am finding that with the amount of gain I often use, that noise is too much, even with a noise gate, the taping down dynamics are lost. Some of my guitars are even star grounded. I also have the suspicion that I am losing complexity of tone, being unbalanced while passive.
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Connecting the grids makes sense if both are grounded. The input triodes are operated in common grid mode, i.e. no signal at the grids.
You can simply lower balanced input impedance by connecting a resistor of desired value between the inputs.

No kind of shielding or wiring can avoid the magnetic hum of single coils. That's why the humbucking principle has been invented.
Star-grounding in a guitar is useless, as there is no hum source inside.