12AX7

Small Signal Triode — Noval

Known Equivalents & Substitutes

ECC83ECC803ECC803S702512AX7A12AX7WA12AX7SM8137CV4004CV492B339B759572160576681772912DF712DT7E21646L138339E83CC

Similar Tubes (Not Drop-In Compatible)

12AT7

Same Noval dual triode pinout but medium-mu (mu=60) vs high-mu (mu=100); higher plate current, lower ra

12AU7

Same Noval dual triode pinout but low-mu (mu=17); much higher plate current, used as driver/buffer

Same Noval dual triode pinout, medium-mu (mu=44); popular in early Fender guitar amp preamps

Same Noval dual triode pinout, reduced mu (mu=70); military grade, common lower-gain substitute

High-mu dual triode (mu=70) but Octal base; similar application as voltage amplifier

Noval pentode with similar high gain capability; different topology but used in similar preamp applications

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Max. Plate Voltage300V

Anode Dissipation (max)Max. Plate Dissipation1W

Cathode Current (max)Max. Cathode Current8mA

Heater-to-Cathode Voltage (max)Max. Heater-Cathode Voltage180V

Max Grid Resistor

Notes

One of the most widely used small-signal tubes in audio, introduced in 1947.
The 7025 is a low-noise, low-hum version intended for high-gain audio preamplifier service.
The 5721 (12AX7WA) is the ruggedized military version with controlled heater warm-up.
The M8137 is the Mullard/CV military equivalent, highly sought after by audiophiles.
The 6057 and 6681 are GE special-quality versions with tighter parameter tolerances.
Can be operated with 6.3V or 12.6V heater supply using the pin 9 center tap.
The 5751 is often used as a lower-gain substitute (mu=70 vs mu=100) for reduced distortion.

Pin Layout — Noval

1Anode 2 (Triode section 2)

2Control Grid 2 (Triode section 2)

3

Socket-Compatible Tubes ⚠ Not electrically compatible

References