Because tubes decay with usage, leaving a tube amp on reduces tube life. Many tubes generate a substantial quantity of heat. This heat has the potential to dry up and damage other components of the amplifier. Tube amplifiers may be dangerous if left on and unattended. The sound can become distorted over time as the amplifier loses its tone control voltage.
It's recommended that you turn off your amplifier by pulling the power cord or switching mode switch. This will stop current flow through the amplifier circuitry, which will shut down any active circuits (such as speakers) connected to it. You should also unplug any cables from the amplifier back to a source of electricity (such as a wall socket), unless they have magnetic power supplies built in. Leaving anything plugged in but inactive will drain battery energy so there is no point in doing this.
If you need to leave your amplifier on but not use it for an extended period, try using it only occasionally as this will reduce the stress on the batteries and help them last longer.
A blown tube can soon become a fire danger in addition to producing heat. The internal parts of a guitar amplifier can also be damaged by excessive heat so care should be taken not to leave any equipment on for too long.
If you do leave your amplifier on for too long, turn it off immediately. If necessary, remove the power supply cord from the amplifier then take all removable panels off the chassis to allow air to flow inside the unit and dispel the heat. You should also check all wiring inside the unit to make sure it is not hot to the touch. Finally, replace all panel screws to ensure that no part of the amplifier was lying across a pin on which power was still being sent after you had turned the unit off.
Blown tubes are usually easy to identify because they have greatly increased sound pressure level (SPL) at which they break down. That is, they produce extremely loud noises when subjected to high voltage currents. The noise produced by a blown tube will likely be very unpleasant to listen to even with closed headphones. A simple test to see if a tube is blown is to connect one electrode to a speaker voice coil and the other to a metal surface on the inner wall of the case.
There is nothing wrong with leaving your amplifier on for an extended period of time. It doesn't wear out the tubes as quickly as if you played it for eight hours straight. Probably much less, because you don't play it, but instead simply leave it. The power supply may need replacing though, since it will fail eventually.
Tube amplifiers, in many circumstances, do not necessitate the level of upkeep that they are known for. As long as you take adequate care of your equipment, buying a tube amp is straightforward and well worth it for the tone. The price of modern tube amps is coming down all the time, so if you can afford it, there's no reason not to buy one.
The best thing about tube amps is their sound. They tend to have more character than solid-state amps and this is because they use vacuum tubes which are basically batteries with leads attached. Batteries need taking out and charging up from time to time just like any other battery-powered device such as phones or radios, but this happens mostly under the hood of the amplifier. All you need to do is plug it in when you want to use it and switch it off when you don't.
There are several different types of tube amp: single-overdrive, dual-overdrive, stacked-power-amp etc. These names will explain themselves. Basically, they are just different arrangements of valves (gates) inside the amp designed to produce certain effects. Single-overdrives are very popular for blues guitarists looking for that classic Chicago sound. Dual-overdrives are great for metal guitarists looking for a bit more bite.
Tubes do get heated. However, in a properly running closed amp, they are just as safe as solid state. Tubes within the amplifier, on the other hand, operate at lethal voltages. They are less safe to build and work on, yet they may be done securely if you take precautions.
Closed amplifiers are less expensive than open ones. Also, many high-end manufacturers use them instead of their more expensive open counterparts because they can sound better (with better quality speakers) than their open-case counterparts. Closed amplifiers are also used in home audio systems because they are less affected by noise from outside sources such as power lines or neighbors' equipment.
However, due to their design, they are more prone to overheating. If this happens, the metal parts will start to warp, causing internal shorts that could ignite any flammable materials inside the case. Also, some components are sensitive to heat exposure. For example, electrolytic capacitors lose up to 30% of their value when exposed to temperatures over 85 degrees Fahrenheit for several hours. This loss is not significant for small units used for personal enjoyment, but it would be unacceptable for larger systems used in studios or live performance settings.
Closed amplifiers produce more heat too! This means that you need more powerful cooling devices to keep them under control. Without proper cooling, your components will overheat and malfunction.