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Tube Amp Facts

If you have never owned a tube amplifier there are some things you need to know!
  • Tube amps sound better than solid state amps- There is actual science behind it. Even order harmonics vs odd order harmonics.  They are also much less fatiguing for long term listening. You can listen to a tube amp for long periods of time even at moderate levels. The first time you listen to your favorite CD with a good tube amp, you will hear things you never heard before. They even make MP3's sound pretty decent.
  • Tube amps sound "louder" than transistor amps- or some people say they sound better loud, either way it has a lot to do with how tube amps distort.  A transistor amp goes from producing a sine wave to a square very quickly, as they distort. A tube amp will produce a sine wave and gradually the tops and bottoms start to go flat as the amp distorts. You can drive a tube amp to a square wave but it is a gradually process. A good tube amp will produce the same amount of "sound" power at 1/2 -1/3 of the power.  
  • Tube amps require maintinnce- As tubes age and over long term use, they gradually loose their ability to produce electrons and eventually they start to sound bad. Tubes can also fail suddenly when the filament burns out (much like an incadescent  light bulb) How long tubes last is dependent on many factors; how close to max plate voltage and current the tubes are run in the circuit, how much air circulation there is for the tubes, and how often they are used and for how long, just to name a few. Many times people may not notice the change in sound and often when their amp gets a "tune up" and some new tubes, they are amazed at how good it sounds. Professional musicians who use tube amps re-tube them every year and recap their tube amps every couple of years.
  • Tube amps produce a great deal of heat- They require air circulation and heat is their enemy. Putting tube amp in a cabinet with no circulation will shorten the tube and amps life. They also can be a problem if you live in a very warm climate and don't use air conditioning. I have one set of SE Amps that use 211 transmitter tubes and will heat a 10 X 15 room in the winter in South Dakota. They also present a danger to children and pets. Tubes run hot and touching an operating output tube will result in 1st to 2nd degree burns without too much trouble.
  • Tube amps are heavy and more expensive than IC amps or the new "Class T or D" amps- Tube amps generally require output and power transformers, that can weigh 10-30 lbs each. These contain iron cores and copper (or even silver) wire. They are expensive to make right and generally 50% of the cost  of a tube amp is in the transformers. A trend in some newer tube amps is to use a switching power supply, to replace the heavy power transformer. I haven't heard one yet that sounded that great. That may be due to the junk tubes that were used in them.
  • Tubes are getting hard to find- Some tubes are becoming hard to find and expensive, but commonly used audio tubes are being manufactured in the Russian Republics and in China. Many Russian tubes  were copies of US tubes and many were made for the Russian military. Several US companies are currently working with manufacturers in Russia to produce high quality audio tubes. For commonly used audio tubes, there is little issue with supply. There are stills stock of USA made tubes offered for sale, but at increasing higher prices. I use many Russian output tubes, they are reliable, and sound very good.  Chinese tubes on the other hand are pretty much junk, sort of like the stuff sold at the dollar store.
  • eBay is a very bad place to buy a tube amp- Most people selling tube amps on eBay have no idea about how to evaluate a tube amp. Any person selling a tube amp and stating the" the tubes light but no further testing done", is either an idiot or a liar. Plugging a tube amp in to power and turning it on would be like putting a battery in a very expensive vintage car and trying to start it without even checking the oil. Tube amps must be connected to a load(speakers or a resistor) and have the AC voltage brought up very slowly(24 hours) if they have been setting for a long time. All this time things need to be monitored. Failure to exercise caution can burn out a power or output transformer. You will also see sellers pulling good tubes and selling them separately to increase profit.