Preamp · Dual triode
12AX7
Same type as ECC83
High-gain dual triode, the most common preamp tube in guitar amplifiers and a frequent choice in hi-fi phono and line stages.
Base: 9-pin miniature (noval)
- Specs checked against a cited datasheet
- No replacement verified yet
Where to buy 12AX7
- Apos AudioNo affiliate relationshipSearch 12AX7 on Apos AudioOpens apos.audio search results
Online audio retailer. Its catalog includes new and new-old-stock (NOS) vacuum tubes, such as 12AX7, 12AT7 and 12AU7 types.
- ReverbNo affiliate relationshipSearch 12AX7 on ReverbOpens reverb.com search results
Online marketplace for new and used music gear, including vacuum tubes.
Each button opens that retailer's own search for 12AX7. We don't see their prices or stock.
Before you buy, check that the listing names 12AX7 or ECC83. A listing that mentions another tube name isn't necessarily the same type. Affiliate disclosure
Other names
- ECC83 same type
European (Mullard–Philips) designation for the 12AX7 type.
- 7025 variant — check before swapping
Low-noise variant designation of the 12AX7 type.
Specifications
Checked against the manufacturer's datasheet. Source: General Electric 12AX7 data sheet ET-T509B, p. 1 (dated 6-53) · checked Nov 5, 2026
From the datasheet: GE describes the 12AX7 as a high-mu twin triode especially suited to resistance-coupled voltage amplifiers, phase inverters, multivibrators and industrial-control circuits where high voltage gain is wanted.
Manufacturer's published ratings from the datasheet above, under the conditions shown. Another manufacturer's tube of the same type may be rated differently; check the datasheet for the tube you have.
| Heater | 12.6 V, 0.15 A (series) / 6.3 V, 0.3 A (parallel) |
|---|---|
| Max plate voltage | 300 V (design-center, each section) |
| Max plate dissipation | 1.0 W (design-center, each section) |
| Max heater-cathode voltage | 180 V (design-center, heater positive or negative) |
| Operating point | Class A1, each section: 250 V plate, −2 V grid |
| Amplification factor | 100 |
| Plate resistance | 62,500 Ω (approx.) |
| Transconductance | 1,600 µmhos |
| Plate current | 1.2 mA |
What these figures mean
- Heater (series / parallel):
- the voltage and current the heater needs. A center-tapped heater can run from a 12.6 V supply (halves in series) or a 6.3 V supply (halves in parallel) (GE 12AX7 data sheet ET-T509B, p. 1).
- Max ratings, design-center:
- limits for a typical tube of the type that equipment should not exceed under normal conditions (GE 12AY7 data sheet, p. 1).
- Max ratings, absolute:
- limits that supply variation, component tolerances and control settings combined must not push past (GE 12AU7-A data sheet ET-T880A, p. 2).
- Operating point:
- the plate and grid voltages at which the figures below it were measured. They describe the tube there, not in any particular amplifier.
- Amplification factor (µ):
- how much the plate voltage varies in relation to the grid (input) voltage (US Navy NEETS Module 6).
- Transconductance:
- how much the plate current varies with the grid (input) voltage (US Navy NEETS Module 6). 1,000 µmhos is 1 mA per volt.
- Plate resistance:
- plate-voltage change divided by plate-current change at a fixed grid voltage; it equals µ divided by transconductance (Lessons in Electric Circuits, “Tube Parameters”).
- Plate current:
- the current each section draws at the operating point shown.
These figures alone don't show whether one tube can replace another; heater, pin connections and ratings must suit your amplifier.
Common uses
- guitar preamp
- phase inverter
- hi-fi preamp