• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

6V6 line preamp

When you have single ended signal and you reverse transfer wires in the electronics you just ground the hot signal side. Diminishes to zero. But speakers are passive transducers that will simply reverse their motion if you reverse the polarity at their terminals. They are current balanced input/output devices by nature. When with purely passive speakers no second thought, they will work on any polarity.

When you do not reverse at the speakers you simply don't have an absolute phase correct audio system if the chain contains some phase reversing component. Like when containing this preamp in gain mode. Buffer mode does not reverse. Doubtful if you hear something worse and on what recordings for that. You try correct and decide. Remember that absolute phase button on some expensive CD players? Was there because recordings differ depending on how the makers processed absolute phase in the chain from mic inputs to issued media. They normally don't even think about that. Its worth maintaining is highly controversial. Its you restore it at the speakers for your system at least because you can. When there is a practical reason like blending mains with subwoofers fed from another point in the chain and the phase is wrong then you must flip it either at the subs or at the mains and don't leave that aspect to chance.
 
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audio note 211 amp use 6v6. but not top model.