Key points
- The 6A7 is a vintage pentagrid converter tube used in AM radios.
- Popular equivalents include 6SA7, 6SB7, and military-grade 5961 tubes.
- 6A7 features a 7-pin base, while equivalents use modern 8-pin octal bases.
📈 6A7 Pinouts
Here is the pinout diagram information for the 6A7 vacuum tube.
Note: Pins 8 and the central key slot connect to the heater circuit.
The symbol “Ключ” under the base drawing in Russian means “key,” indicating the alignment notch.
| Pin Number | Connection |
| 1 | Cathode (K) |
| 2 | Grid 1 (Control Grid) |
| 3 | Grid 3 |
| 4 | Grid 5 (Suppressor Grid) |
| 5 | Plate (Anode) |
| 6 | Grid 2 (Screen Grid) |
| 7 | Grid 4 (Oscillator Anode) |
| 8 | Heater (Filament) |
📊Popular 6A7 Tube Equivalents
- The 6SA7 is considered the direct successor to the 6A7. It performs the same pentagrid converter function but uses a more modern 8-pin octal base instead of the older 7-pin UX7. The 6SA7 also provides improved shielding and stability, making it more reliable in post-war radio designs.
- The 6SB7 offers higher frequency performance and better internal shielding compared to the 6A7. Like the 6SA7, it uses an octal base, so it’s not directly interchangeable without modifying the socket. The 6SB7 is preferred in more advanced or custom-built radio circuits where reduced noise and better RF performance are important.
- The 5961 is a military-grade equivalent of the 6A7. It has a rugged construction designed to handle higher voltages and harsher environmental conditions. The 5961 also uses an octal base and is ideal for military and industrial radio equipment rather than standard consumer radios.
6A7 vs. 6SA7: Which One to Choose?
- Base Type: The 6A7 uses a 7-pin large UX7 base, while the 6SA7 uses the more modern 8-pin octal base. This means the 6SA7 won’t fit into a 6A7 socket without rewiring or an adapter.
- Electrical Characteristics: Both function as pentagrid converters, but the 6SA7 has slightly improved shielding and stability, making it better for stronger or clearer radio reception.
- Durability: The 6SA7 is generally considered more reliable due to its later production and better materials compared to the older 6A7.
- Application: 6A7 was common in 1930s–1940s radios. 6SA7 became the standard in the post-war era as radios transitioned to octal sockets.
6A7 vs. 6SB7: Key Differences and Similarities
- Frequency Performance: The 6SB7 offers improved performance at higher RF frequencies compared to the 6A7, which was primarily designed for AM broadcast bands.
- Base Type: Again, 6SB7 uses an octal base, unlike the 6A7’s UX7. This limits direct replacement unless socket modification is performed.
- Noise Reduction: The 6SB7 features improved internal shielding, which reduces signal noise—beneficial for sensitive radio equipment.
- Application: 6SB7 is suited for more advanced or custom radio circuits, while 6A7 fits vintage AM radios.
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6A7 vs. 5961: Are They Interchangeable?
- Build Quality: The 5961 is a military-grade pentagrid converter, meaning it is more rugged and has a longer lifespan than the civilian-grade 6A7.
- Base Type: Like the 6SA7 and 6SB7, the 5961 uses an octal base, while the 6A7 uses UX7. Socket conversion would be necessary for substitution.
- Voltage Tolerance: The 5961 can handle higher voltages and more extreme environmental conditions, unlike the standard 6A7.
- Application: 5961 is ideal for military or industrial radio equipment requiring long service life, whereas 6A7 is more for consumer-grade radios.
🎚️6A7 tube Datasheet:
| Parameter | Value |
| Tube Type | Pentagrid Converter (Mixer/Oscillator) |
| Base Type | UX7 (7-pin Large) |
| Heater Voltage (Uf) | 6.3 V |
| Heater Current (If) | 300 mA |
| Plate Voltage (Va max) | 250 V |
| Screen Grid Voltage | 100 V |
| Oscillator Grid Voltage | Typically 20–40 V |
| Transconductance (S) | ~1.1 mA/V |
| Internal Resistance | ~0.5 MΩ |
| Typical Application | AM Radio Mixer and Oscillator |
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