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Most people think vacuum tubes have been replaced by solid-state electronics. However, vacuum tubes have some distinct characteristics which can really help tweak the sound of your amplifier in a desirable way. In this article, we’d like to cover the differences between 2 of the more common vacuum tubes, the 12bh7 vs12au7.
The main differences between these two tubes are their frequency response, gain factor, and maximum anode dissipation. The 12AU7 has a lower frequency response of about 50Hz and the 12BH7 has a higher frequency response of about 10kHz. The 12AU7 has a lower gain factor than the 12BH7. The maximum anode dissipation of the 12AU7 is 10W and that of the 12BH7 is 25W.
Another clear difference is that these two types of tubes have different operating voltages as well as dissipation rates (watts). While 1A BH7 has an operating voltage range of 6 to 75 volts, 1A AU7 has an operating voltage range of 6 to 60 volts only. As far as dissipations go, 1A BH7 dissipates 1 watt at its maximum while 1A AU7 dissipates 0.5 watts at its maximum output power level only.
When you want to build your own tube amplifier or use them in other applications, it’s important to know what each type does best so that you can choose the right one for your needs.
An-In-Depth Overview 12BH7 vs 12AU7
If you’re looking to upgrade your amplifier, two popular vacuum tubes to consider are the 12BH7 and 12AU7. Both are used as preamp tubes, but they have distinct differences in characteristics and applications.
12BH7 Vacuum Tube
A 12bh7 tube is a vacuum tube for amps. It’s used in the preamp and phase inverter sections of an amp and works as a voltage amplifier.
The 12bh7 is a low-noise triode that’s often used to buffer other tubes in the preamp section of an amplifier. The 12bh7 has high gain and low distortion characteristics, making it ideal for use as a voltage amplifier in other circuits. It is used in a variety of applications, but it is most commonly found in guitar amplifiers.
The 12bh7 is a beam power tube that can handle up to 150 volts and 100 watts of power. It has an octal base and uses between 45 and 65 volts to operate properly. The main function of this type of vacuum tube is to amplify audio signals before they reach the power amp section of an amplifier. Its job is to pass high voltages from the power supply through the tubes themselves without distorting or changing the sound quality of what’s being played.
A 12BH7 tube works by amplifying sound coming from an audio source such as a guitar or microphone. It amplifies this sound so that it can be sent through speakers so that it can be heard by people who cannot hear well enough to hear these sounds otherwise.
12AU7 Vacuum Tube
A 12AU7 tube is a vacuum tube for amps. 12AU7 tubes are the most commonly used preamp tubes. They have a warm, rich tone and are great for clean sounds. They also work great in lower-wattage amps that don’t need the power of a 6L6GC or 6V6GT.
The 12AU7 tube is classified as a medium gain preamp tube, which means that it can handle high levels of distortion without breaking down as some other preamp tubes might.
A 12AU7 tube is a dual triode vacuum tube that has two electrodes, one filament, and one plate (anode). The cathode is indirectly heated by the filament which acts as the cathode’s heater filament. The filament supplies current to the cathode and heats it up until it starts glowing red hot when powered by an AC current source (rectifier).
Once heated, electrons are emitted from the cathode’s surface and travel through the grid wire to reach the plate electrode where they are collected by an external circuit (speaker).
Differences Between 12BH7 vs 12AU7
When it comes to vacuum tubes, the 12BH7 and 12AU7 are two of the most popular types. While they might look similar, they have some key differences that can affect their performance and sound quality. Here are some of the main differences between the two:
1. Gain & Gain Bandwidth
Gain refers to the amount of amplification an amplifier provides, while gain bandwidth describes how much range of frequencies it can amplify. The higher the gain bandwidth, the better the amplifier. The 12AU7 has a gain bandwidth of 25MHz, while that of a 12BH7 is about 20MHz.
2. Input & Output Impedance
The 12AU7 has a high input impedance, meaning it is easy to drive. The 12BH7 has a low input impedance, meaning it is harder to drive.
If you have an amplifier with a high output impedance and are looking for a tube that will be easy to drive, consider the 12AU7. If you want something with lower output impedance and don’t mind losing some gain in your signal chain, you may want to choose the 12BH7
3. Dissipation rates
The dissipation rate is the maximum power that a tube can handle without overheating. The higher the dissipation rate, the more power your amp will be able to handle before it starts getting too hot and causing damage.
The 12AU7 has a lower dissipation rate than the 12BH7, so it’s best used in low-power applications. If you have an amplifier or preamp with 300W per channel or less, this is probably what you want to use there. It’ll help prevent overheating and keep things running smoothly for years without fail.
4. Size
The 12AU7 is significantly larger than the 12BH7. This means that it will take up more space and require more power to run. The size difference also makes it less durable and harder to repair if damaged.
The 12AU7 has a somewhat wider frequency response range compared to the 12BH7, which means it can produce more sounds across a broader spectrum of frequencies.
5. Power
As we mentioned above, 12AU7 has a higher plate dissipation of 1.5W, while 12BH7 has a lower plate dissipation of .5W. This means that if you’re using the same voltage for both tubes (say 150V), then with more current passing through the tube and less resistance to overcome in order to get there, 12AU7 will be operating at its optimal point almost immediately.
Whereas 12BH7 will need more time before it begins working properly in your circuit designs – this is especially true if they’re driving an output stage with no input capacitance or series resistance present as these two factors also tend to slow down how quickly voltage builds up within a vacuum tube circuit.
6. Noise
Because of the extra gain, the 12BH7 has a higher noise level than the 12AU7. The high-gain variants of this tube are also less noisy than the low-gain variants, though not by much.
The 12AX7 is slightly noisier than either variation of the 12AU7; however, its noise floor is still noticeably lower than that of any equivalent 12BH or AT variant. This makes it an ideal choice for use in high-gain circuits such as amplifiers or preamps where you need to keep your signal clean and free from hum.
7. Sound quality
The 12au7 has a higher gain than the 12bh7 and can be used in circuits where slightly more drive is desired. It’s also more efficient and generates less noise, but has a narrower bandwidth, which means that it’s less capable of producing low frequencies.
The 12bh7 is not as efficient as the 12au7, but has a wider bandwidth and lower noise level, making it ideal for use in high-end amplifiers or tube preamps where variability isn’t desirable.
8. Application
The 2 tubes are different in some ways. The 12au7 is used in guitar amps and the 12bh7 is used for hi-fi amps. Most people see this as a disadvantage because it means that if you have an amp that uses the 12bh7, then you cannot replace it with another tube.
Choosing the right vacuum tube for your audio system depends on your specific needs and preferences. If you’re looking for a tube with higher gain and wider bandwidth, the 12AU7 might be the better choice. However, if you need a lower output impedance and lower noise level, the 12BH7 might be the way to go. Ultimately, it’s all about finding the right balance between gain, bandwidth, and sound quality for your particular application.
FAQs on 12BH7 vs 12AU7 Tubes
Can I Replace 12AU7 with a 12AT7 Vacuum Tube?
Yes, you can replace the 12AU7 with a 12AT7 vacuum tube. Both tubes have the same pin structure, but they have some differences. The 12AT7 is usually used in audio applications, while the 12AU7 is commonly found in low-voltage output stages or as a driver tube for other tubes.
Can you use a 12AT7 in place of a 12AU7?
Yes, you can use a 12AT7 in place of a 12AU7. The 12AX7, 12AT7, and 12AU7 belong to the same family of twin triode tubes and are often interchangeable.
Can I use a 12AU7 in place of a 12AX7?
You can interchange a 12AX7 with 12AT7, 12AU7, 12AY7, or 5751 as they have the same pin structure. However, each tube has a different gain factor, so you will get different results in your amp.
Do you need to match preamp tubes?
With preamp tubes, you don’t need to worry about matching pairs or biasing, unlike power tubes. As long as your new tube is the same model as what you’re replacing, such as 12AX7, 12AT7, or 6SN7, you’re good.
Final Thoughts on 12BH7 vs 12AU7 Vacuum Tubes
You may find that the two tubes are very similar, but there are three main differences that you should consider when looking for a new tube. The 12au7 can be used to reduce the amount of noise in an amp because it’s quieter than a 12bh7.
The 12au7 is smaller than a 12bh7, and this can affect how it fits into your amplifier or power supply circuitry. And, the 12bh7 requires more power than the other vacuum tubes and may not fit inside some amps if they’re using an all-tube setup; a combination of vacuum tubes and solid-state transistors.
These tubes have different characteristics, but they all work well in the right applications. If you are looking to upgrade your amp with a new tube. Start by finding out what kind of sound signature you want and how much power your amp can handle. Then decide which of the two tubes will provide that sound signature and power requirement with the least amount of noise for your budget.
