The 12AX7 is a miniature dual triode vacuum tube that has been used in a variety of audio equipment since its introduction in the 1940s. This tube has become a staple in guitar amplifiers, hi-fi preamplifiers, and various other audio devices due to its high gain, low noise, and versatility. The 12AX7 datasheet provides detailed information about the electrical characteristics of this tube. It includes specifications such as maximum ratings, typical operating conditions, and performance curves for various parameters. This information is crucial for designers and technicians who want to optimize the performance of their circuits and ensure the longevity of their equipment.
The 12AX7 is a high-gain, low-noise, and low-microphonic tube. It is commonly used in preamp and driver stages of audio amplifiers, guitar amplifiers, and other electronic devices. Here are some of the key features of the 12AX7:
- High voltage gain: The 12AX7 has a voltage gain of around 100, which makes it suitable for amplifying weak signals from microphones, guitars, and other sources.
- Low noise: The 12AX7 has a low internal noise level, which helps to preserve the quality of the input signal.
- Low microphonics: The 12AX7 is designed to minimize the effect of mechanical vibrations and shocks, which can cause unwanted noise and distortion.
- High input impedance: The 12AX7 has a high input impedance, which allows it to interface with a wide range of signal sources without loading them down.
- Low output impedance: The 12AX7 has a low output impedance, which allows it to drive long cables and other loads without losing signal quality.
- Long life: The 12AX7 is a rugged and reliable tube that can last for many years with proper care and maintenance.
Overall, the 12AX7 is a versatile and dependable tube that has been used in countless audio and electronic applications over the years. Its high gain, low noise, and low microphonics make it an excellent choice for preamp and driver stages, while its long life and rugged construction ensure that it will continue to be a popular choice for years to come.
Read on for more detail and then we have an illustrated version of the 12ax7 datasheet.
Section 3: Electrical Characteristics
The 12AX7 is a high-gain, low-noise, dual triode vacuum tube. It has a maximum plate voltage rating of 330V and a maximum plate dissipation rating of 1.2 watts. The tube has a heater voltage of 6.3V and a heater current of 0.3A. Its amplification factor (mu) is typically between 60 and 100, and its transconductance (gm) is typically between 1.6 and 2.2 mA/V.
The following table summarizes the typical electrical characteristics of the 12AX7:
|Amplification factor (mu)||60-100|
|Transconductance (gm)||1.6-2.2 mA/V|
|Plate resistance (rp)||62.5 kohms|
|Gain bandwidth product (gbp)||6 MHz|
It’s worth noting that the actual electrical characteristics of a specific 12AX7 tube can vary from the typical values listed above. The electrical characteristics can also change over time as the tube ages and wears out. Therefore, it’s important to consult the datasheet for the specific 12AX7 tube being used in a circuit to ensure proper performance.
The 12AX7 is a small, nine-pin miniature tube that measures approximately 47mm in length and 22mm in diameter. The pins are arranged in a circular pattern around the base of the tube, with a 12.7mm spacing between each pin. The tube is typically mounted horizontally, with the pins inserted into a socket on a circuit board or chassis.
The tube’s glass envelope is made of high-quality borosilicate glass, which is resistant to thermal shock and mechanical stress. The envelope is designed to withstand high temperatures and pressures, making it suitable for use in a wide range of applications.
The tube’s internal construction consists of a cathode, two grids, and an anode. The cathode is a small, heated filament that emits electrons when heated to a high temperature. The grids are metal screens that control the flow of electrons from the cathode to the anode. The anode is a metal plate that collects the electrons and converts them into an electrical signal.
The 12AX7 is a rugged and reliable tube that can withstand a wide range of operating conditions. It has a maximum plate voltage of 330 volts and a maximum plate dissipation of 1.2 watts. The tube’s heater requires 6.3 volts and 300 milliamps of current to operate, making it compatible with a wide range of power supplies.
|Number of Pins||9|
|Maximum Plate Voltage||330V|
|Maximum Plate Dissipation||1.2W|
The 12AX7 is a nine-pin miniature tube, and its pins are arranged in a circular pattern. The pins are numbered clockwise from 1 to 9 when viewed from the bottom of the tube, with pin 1 being at the bottom left corner. The following table shows the pinout of the 12AX7:
|Pin Number||Pin Name||Description|
|1||Cathode||The cathode is the negative electrode of the tube and is connected to ground in most applications.|
|2||Grid 1||Grid 1 is the first control grid and is used to control the flow of electrons between the cathode and the anode.|
|3||Plate (Anode)||The plate is the positive electrode of the tube and is connected to the high voltage supply in most applications.|
|4||Heater||The heater is used to heat the cathode and is typically connected to a 6.3V AC supply.|
|5||Unconnected||This pin is not connected internally and is typically left unconnected in most applications.|
|6||Grid 2||Grid 2 is the second control grid and is used to further control the flow of electrons between the cathode and the anode.|
|7||Unconnected||This pin is not connected internally and is typically left unconnected in most applications.|
|8||Cathode||The cathode is the negative electrode of the tube and is connected to ground in most applications.|
|9||Shield||The shield is used to reduce interference from external sources and is typically connected to ground.|
The pin configuration of the 12AX7 is important to understand when designing circuits that use this tube. The cathode and plate are the most important pins, as they are used to control the flow of electrons through the tube. The heater is also important, as it is used to heat the cathode and must be connected to the correct voltage supply. The grid pins are used to control the flow of electrons between the cathode and the anode, and the shield is used to reduce interference from external sources.
The 12AX7 is a versatile tube that finds use in a wide range of audio applications. Here are some of the most common applications:
- Preamp tubes: The 12AX7 is often used as a preamp tube in guitar amplifiers, hi-fi systems, and other audio equipment. It is prized for its high gain and low noise characteristics, which make it ideal for amplifying weak signals from microphones and instruments.
- Tone control circuits: The 12AX7 is also commonly used in tone control circuits, where it can be used to shape the frequency response of an audio signal. By adjusting the gain and frequency response of the 12AX7, engineers can create a wide range of tonal variations.
- Power amplifiers: While the 12AX7 is not typically used as a power amplifier on its own, it is often used in conjunction with other tubes to create high-powered amplifiers. For example, it is common to see a 12AX7 used in the preamp stage of a guitar amplifier, with one or more power tubes (such as EL34s or 6L6s) used in the output stage.
- Effects pedals: The 12AX7 is also used in many guitar effects pedals, such as overdrive, distortion, and fuzz pedals. In these applications, the 12AX7 is used to amplify and distort the guitar signal, creating a wide range of tonal effects.
Overall, the 12AX7 is a versatile and popular tube that has found use in a wide range of audio applications. Whether you’re building a guitar amplifier, a hi-fi system, or a guitar effects pedal, the 12AX7 is a tube that you should definitely consider.
Characteristics And Typical Operations
Class A Resistance-Coupled Amplifier
Average Plate Characteristics
Average Transfer Characteristics
Conclusion – 12ax7 datasheet
After reviewing the 12AX7 datasheet, it is clear that this vacuum tube is a versatile and reliable option for a wide range of audio applications. Its high gain, low noise, and low microphonics make it a popular choice for guitar amplifiers, preamplifiers, and other audio equipment.
The datasheet provides valuable information on the tube’s electrical characteristics, including its maximum ratings, heater voltage and current, and amplification factor. It also includes a detailed pinout diagram, which is essential for properly wiring the tube in a circuit.
While there are many other vacuum tubes available on the market, the 12AX7 remains a popular choice due to its availability, affordability, and performance. Whether you are a musician, audio engineer, or hobbyist, the 12AX7 datasheet is a valuable resource for understanding this classic tube and its capabilities.