12AX7
12AX7 is also designated ECC83. Completed sales put the typical price at $49.06 per tube.
The 12AX7 is a miniature indirectly heated twin triode, with two separate triode structures mounted side by side in a standard T6½ bulb; only the heater connections are common between the two units.
Construction
Each triode unit is a separate structure, and the heater centre tap on pin 9 enables use in both AC and AC/DC equipment. The tube is based with a BVA standard base type B9A. Each triode unit has characteristics somewhat similar to a 6F5G/GT.
Ratings
The heater may be operated in series at 12.6 volts and 0.15 ampere, or in parallel at 6.3 volts and 0.3 ampere. Maximum ratings include: heater-cathode potential (DC) 250 volts, anode voltage 300 volts, anode dissipation 1.0 watt, cathode current 8 mA, negative control grid voltage 50 volts, and positive control grid voltage 0 volts.
Applications
The 12AX7 is suitable for use as a resistance coupled amplifier and as a paraphase amplifier. When used in cascade, a separate bias resistor, suitably decoupled, is essential for each cathode. The Brimar datasheet gives typical values for a normal paraphase circuit with a peak push-pull output of approximately 100 volts, and for an anode-cathode load phase splitter with a peak push-pull output of approximately 75 volts. In an example with a 250 volt supply and a 470,000 ohm anode load, the amplification factor is 97 and the anode impedance is 109,000 ohms.
| Designation | Evidence | Confidence |
|---|---|---|
| ECC83 | 75 independent documents | strong |
Equivalence is asserted only where the archive's own literature states it directly, in at least 40 separate documents. Tubes that merely substitute in some circuits are not listed here.
Base B9A, viewed from below (the wiring side), pins numbered clockwise from the key. Hand-verified.
| Measure | Per tube |
|---|---|
| Median | $49.06 |
| Typical range (25th–75th) | $28.23 – $81.95 |
| Most sales (10th–90th) | $17.75 – $137.50 |
| Extremes incl. outliers | $2.23 – $2,568.75 |
| Completed sales | 758 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| Telefunken | $86.75 | $64.34 – $110.48 | 109 |
| RCA | $43.67 | $29.94 – $65.00 | 108 |
| Mullard | $76.15 | $50.00 – $137.95 | 84 |
| GE | $33.94 | $21.67 – $55.99 | 74 |
| Sylvania | $38.98 | $27.50 – $54.95 | 61 |
| Amperex | $87.74 | $56.07 – $137.99 | 47 |
| Tung-Sol | $34.36 | $24.85 – $49.90 | 30 |
| Philips | $69.48 | $50.96 – $91.25 | 27 |
| JJ | $20.44 | $18.95 – $33.08 | 16 |
| Raytheon | $43.24 | $29.95 – $68.47 | 14 |
| Sovtek | $26.94 | $21.75 – $35.90 | 12 |
| Valvo | $56.60 | $48.81 – $153.97 | 10 |
| Condition | Median | Sales |
|---|---|---|
| new | $33.87 | 4 |
| NOS | $63.45 | 221 |
| used | $44.99 | 375 |
| current | $25.52 | 48 |
Per-tube prices from completed sales, 2025-08-14 to 2026-11-08. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 12AX7, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| Brimar | 12AX7 | PDF (1011 KB) |
| General Electric | 12AX7 | PDF (292 KB) |
| Sylvania | 12AX7 | PDF (281 KB) |
| Tung-Sol | 12AX7 | PDF (151 KB) |
| Tesla | ECC83 | PDF (2385 KB) |
| Ei | ECC83 | PDF (685 KB) |
| Philips | ECC83 | PDF (463 KB) |
| Philips | ECC83 | PDF (149 KB) |
| RFT | ECC83 | PDF (92 KB) |
Documents held here and used to write this page.
- Charakteristické hodnoty: (filed under ECC83)
- BRIMAR
5 further designations appear alongside 12AX7 in the literature but below the evidence threshold used here, so they are not listed as equivalent.