6N2P tubes are a replacement for 12AX7 in any typical amp application, but they have 6.3V heater voltage and would need a different wiring than stock 12AX7's.
Q: How do I rewire the socket to use such tubes?
A: 12AX7's filaments can be connected for either 12.6V (pins 4 and 5) or 6.3V (pin 9 and pins 4 and 5 connected together) operation. 6N2P's filament will take only 6.3V (pins 4 and 5).
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