7581A
7581A has no equivalent designation confirmed by the archive. Completed sales put the typical price at $78.77 per tube.
The 7581A is a beam-power pentode intended primarily for audio-frequency power-amplifier applications. It has a coated unipotential cathode, a T-12 glass envelope, and a B6-148 short medium-shell octal 6-pin Micanol base. The tube can operate in any position.
Construction
The heater is rated at 6.3 volts, with heater current specified at that voltage. Pin 2 and pin 7 are the heater connections, pin 3 is the plate, pin 4 is grid number 2 (screen), pin 5 is grid number 1, and pin 8 is the cathode and beam plates.
Ratings
The maximum plate voltage is 500 volts. The maximum screen voltage is 450 volts, except in push-pull circuits where the screen of each tube is connected to a tap on the plate winding of the output transformer, in which case the maximum screen voltage is 500 volts. Maximum screen dissipation is 5.0 watts.
Characteristics
Grid-number 1 to plate capacitance is 0.6 picofarad. In triode connection, the amplification factor is 8, plate resistance is approximately 1700 ohms, and transconductance is 4700 micromhos. At a plate voltage of 250 volts, plate resistance is approximately 22,500 ohms and transconductance is 6000 micromhos. The 7581A is unilaterally interchangeable with the 7581 and the 6L6-GC. The General Electric Company datasheet for the 7581A is dated February 10, 1959.
| Measure | Per tube |
|---|---|
| Median | $78.77 |
| Typical range (25th–75th) | $49.36 – $85.78 |
| Most sales (10th–90th) | $44.99 – $252.50 |
| Extremes incl. outliers | $29.25 – $252.50 |
| Completed sales | 10 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| Philips | $86.64 | $85.78 – $252.50 | 3 |
| Tung-Sol | $49.36 | $29.25 – $79.99 | 3 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $85.49 | 5 |
Per-tube prices from completed sales, 2026-07-04 to 2026-09-29. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 7581A, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| General Electric | 7581A | PDF (843 KB) |
| Tung-Sol | 7581A | PDF (142 KB) |
Documents held here and used to write this page.
- **BEAM PENTODE**