5691
5691 has no equivalent designation confirmed by the archive. Completed sales put the typical price at $77.00 per tube.
Description
The 5691 is a high-mu twin triode, designed and manufactured for critical industrial applications. It is particularly useful as a voltage amplifier. The heaters for the two triode units are connected in series.
Construction
The 5691 is similar to the 6SL7-GT except that it has twice the heater current (0.6 ampere). It uses a pure tungsten heater for unipotential cathodes. The bulb is T-9. The base is Short Intermediate-Shell Octal 8-Pin, with External Barriers, Non-Hygroscopic.
Ratings and Physical Characteristics
The heater voltage is 6.3 volts. The maximum overall length is 2-7/8 inches, the maximum seated length is 2-5/16 inches, and the maximum diameter is 1-9/32 inches.
Mechanical Durability
The 5691 can withstand impact shocks of 500g for short periods, and 2.5g of continuous vibration for hundreds of hours.
Electrical Characteristics
The electrical characteristics of the 5691 are very similar to those of the 6SL7-GT.
| Measure | Per tube |
|---|---|
| Median | $77.00 |
| Typical range (25th–75th) | $57.97 – $94.00 |
| Most sales (10th–90th) | $26.98 – $126.80 |
| Extremes incl. outliers | $15.16 – $395.00 |
| Completed sales | 35 |
| Brand | Median | Range | Sales |
|---|---|---|---|
| RCA | $77.84 | $60.83 – $94.00 | 29 |
| Condition | Median | Sales |
|---|---|---|
| NOS | $87.97 | 18 |
| used | $57.72 | 15 |
Per-tube prices from completed sales, 2026-02-25 to 2026-09-13. Matched pairs and quads are divided out. See the price index for how these move over time.
Original manufacturer datasheets for 5691, hosted by Frank Philipse's Electron Tube Data sheets.
| Manufacturer | Designation | Datasheet |
|---|---|---|
| RCA | 5691 | PDF (942 KB) |
| RCA (HB3) | 5691 | PDF (258 KB) |
Documents held here and used to write this page.
- RCA