6CA4
6CA4 is also designated EZ81. Completed sales put the typical price at $29.00 per tube.
Description
The 6CA4 is a miniature, heater-cathode, twin diode intended for full-wave rectifier operation. It has a coated unipotential cathode, a T-6 1/2 glass envelope, and an E9-1 small button 9-pin base. The tube can be mounted in any position.
Construction
Pin assignments are as follows: pin 1 is plate number 2, pin 3 is the cathode, pins 4 and 5 are the heater, and pin 7 is plate number 1. Pins 2, 6, 8, and 9 are internal connections.
Ratings
The 6CA4 data is presented using Design-Maximum ratings. The peak inverse plate voltage rating is 1200 volts, and the steady-state peak plate current per plate rating is 500 milliamperes. The heater-cathode voltage rating, with the heater negative with respect to the cathode, is 500 volts. The tube voltage drop is 20 volts at 150 milliamperes DC per plate.
Applications
According to the General Electric datasheet dated August 25, 1959, the high output current and small size of the 6CA4 make it especially suitable for compact amplifier designs.
| Designation | Evidence | Confidence |
|---|---|---|
| EZ81 | 62 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.
| Measure | Per tube |
|---|---|
| Median | $29.00 |
| Typical range (25th–75th) | $21.54 – $36.49 |
| Most sales (10th–90th) | $18.00 – $97.45 |
| Extremes incl. outliers | $15.47 – $1,417.65 |
| Completed sales | 39 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| RCA | $21.09 | $18.00 – $24.65 | 8 |
| Mullard | $49.99 | $31.94 – $97.45 | 7 |
| GE | $25.99 | $21.00 – $28.45 | 5 |
| Amperex | $36.49 | $25.27 – $36.98 | 3 |
| Raytheon | $31.55 | $29.89 – $34.92 | 3 |
| JJ | $21.95 | $18.79 – $32.88 | 3 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $31.94 | 15 |
| used | $28.45 | 15 |
| current | $26.07 | 4 |
Per-tube prices from completed sales, 2026-02-09 to 2026-09-21. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 6CA4, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| General Electric | 6CA4 | PDF (502 KB) |
| Tung-Sol | 6CA4 | PDF (277 KB) |
| RCA (HB3) | 6CA4 | PDF (98 KB) |
| Philips | EZ81 | PDF (637 KB) |
| Mazda-Belvu | EZ81 | PDF (594 KB) |
| Tesla | EZ81 | PDF (460 KB) |
| JJ | EZ81 | PDF (184 KB) |
| Philips | EZ81 | PDF (171 KB) |
| RFT | EZ81 | PDF (72 KB) |
| La Radiotechnique | EZ81 | PDF (55 KB) |
| Brimar | EZ81 | PDF (54 KB) |
Documents held here and used to write this page.
- 6CA4
- EZ81 (filed under EZ81)
2 further designations appear alongside 6CA4 in the literature but below the evidence threshold used here, so they are not listed as equivalent.