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 Tubes n' Tips for Guitar Amps

The humble Guitar Tube or Valve (UK) can make or break your sound if your using one of these old-style design but wonderful sounding amps. It's well worth your while to find a good source of manufacturer.

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Guitar Amplifiers - Tubes and Trannys

Tubes or Valves as there called in the UK, are an old design still used by Guitar Amplifier manufactures today, because they inherently give the Amp and Guitar a traditionally "Warm" sound.

Transistors were invented in 1948 and hit the streets back in the '55, in the form of the new-fangled Transistor Radio. Many consumer goods of the time, replaced the up-till-then used Tubes with their new electronic equivalent the "Tranny" - the TV is one of the most famous examples.

Cheaper to produce and smaller in size and design, these Transistorized models soon became par for the course. But the makers of audio equipment such as Guitar Amps realizes that the old Tube design gave a special sound which still hasn't been totally successfully emulated by the Transistor as we speak.

So it looks like the oul' Tube Guitar Amplifiers won't be going away for the moment and are still as popular today as when they first came out. Here's a few Tube tips and pointers used by Guitar Amp Tube-Heads the world over.

Tubes n' Tips

The difference in Tube and Transistorized Guitar Amp sounds, is a traditionally and historically hot debate in Guitar circles of course. I think at the end of it all, it depends a lot on personal taste. I personally prefer an all Tube Amp but that's just my taste. There are many players such as Jazz heads and Nu-Metallers who love the metallic cut of an overdriven Transistor Amp. Jazzers love their tight and clean sound and so on.
  • Tube Tips An All Tube Amp will contain transistorized components too. It is the Pre and Power-Amp sections we are interested in. This is where the Guitar Amplifier gets it's most characteristic sounds from.
  • Tube Tips In general, the Pre-Amp section Tubes gives you access to the Dirty sound.
  • Tube Tips The Power-Amp section is responsible for authentic Audio Output.
  • Tube Tips In simple terms, Tubes are used as a way of regulating the flow of voltage in a circuit, so they are in effect "Valves". This is the UK equivalent name.
  • Tube Tips Different Tubes are used in various sections of the Pre and Power-Amp sections for many purposes including:
  • Amplifying weak signals
  • Driving the Distortion Channel
  • Supplying regulated voltage to other tubes
  • Inverting the Output Tube's Phase
  • Increasing Audio Output
It all boils down to the sound coming out of your Amp in the end, so it's well worth the while taking the time to check 'em out as each Tube or stage of the signal is vital to get right.
  • Tube Tips Always use the Standby Switch on your Amp to lengthen Tube life.
  • Tube Tips Hybrids are Guitar amps that use a Tube only in the Pre-Amp. This is used to give the overdrive or distortion channel a nice creamy sound. The rest of the Amp is Transistorized.
  • WARNING NEVER work on any mains powered Guitar Amplifiers or Electrical Equipment unless you know exactly what you are doing! Even with the plug out of the socket, many appliances are capable of holding and producing LETHAL charges!
  • Tube Tips If you fit Output Tubes yourself get the bias done by your Service Technician for best sound and Tube-lifespan reasons.
  • Tube Tips Buy only the best Tubes you can get - it's worth it for the sound. Some of the good makes and suppliers include:
Groove Tubes (USA)
Watford Valves (UK)

The Pre-Amp Section

  • Tube Tips The same Tube type can have 2 names - one for the USA and a different code for the UK. Common Tubes found in the Pre-Amp section would be
              USA Tube Name EEC81 - Uk Equivalent = (12AT7)
              USA Tube Name EEC82 - Uk Equivalent = (12AU7)
              USA Tube Name ECC83 - Uk Equivalent = (12AX7)                             
  • Tube Tips If your local tech shop doesn't stock the Tubes you want you can buy them yourself, fit them if your competent, and just get the shop to check and regulate the bias etc. This can save you cash big time on hourly rates.
  • Tube Tips Make sure to buy reputable Tubes that have been put thru rigorous tests and checked for stability, microphonics, distortion tests, hum and so on - so avoid the cheapies.
  • Tube Tips If you buy a set in a box it's usually on the packaging that it's a matching set but the Bias still should be checked and set by your guitar-amp tech.
  • Tube Tips On average you'll need to change the Tubes every 6-12 months depending on use and other factors. This is one small price you pay to get that Tube Tone.
  • Tube Tips Carry spares with you as, like light bulbs, Tubes can blow at any time.
  • Tube Tips Some players just leave 'em in and get on with it, but try to carry spares in this case.

The Power Amp and famous Manufacturers

Here's 2 common Amplifier Power Amp set-up Tubes used -
  • The Peavey Classic 50w: 4 x EL84 (6BQ5)
  • Classic Marshall Lead Stack 100w: 4 x EL34 (CV1741)
  • Other Common Output Tubes: 6L6GC, 6V6GT, 5881, 6550, 7027A, T66, KT88.
Famous Tube Amp Manufacturers worth trying include:
  • Marshall
  • Fender
  • Soldarno
  • Vox
  • Orange
  • Peavey
  • Hughes and Kettner
  • Mesa Boogie
  • EVH/Peavey
  • Guild
  • Acoustic
  • Sunn
  • Ampeg
  • Carvin
See our Guitar Amplifiers for more detailed info.
Many players go thru many different makes of Tube before they finally settle for the ones they like.
  • Tube Tips Tubes can be replaced with a similar type for different sound options such as replacing the Ist Pre-Amp 12AX7 Tube with a 12AY7 on a '59 Fender Bassman or reissue. Do this with the Amp PLUGGED OUT! This results in less gain/volume but more overdrive qualities - useful to overdrive the Amp even more without drowning out your fellow band members or for playing a low-key gig etc.
  • Tube Tips You can do some investigation and find out if any changes can be made to your particular Valve Amplifier by using this substitution method.
  • Tube Tips This is called Tube Substitution. Be careful that you know exactly which substitution to use before trying this. The wrong Tube in the wrong place can fry your Amp. You can find some excellent Tube Substitution Info links on our Resources page.
  • Safety Tips It's usually easy to change them yourself if necessary in an emergency, but NEVER work on any mains powered Guitar Amplifiers or Electrical Equipment unless you know exactly what you are doing! Even with the plug out of the socket, many appliances are capable of holding and producing LETHAL charges!

Common Sick Tube Symptoms

  • No glow inside the glass when powered up in Standby mode.
  • Red spots appearing on the plate of the valves.
  • Blue/Silver marks on the glass (colors not unlike an oil slick).
  • Black burn marks on the glass.
  • Weak sound - not quite what it used to be.
  • Crackle or noise coming from the speakers.
  • Bad performance all round - not ALWAYS the Tubes.
  • Noise and Crackle when suspected Tube is tapped with a Pencil - Amp turned fully on. This test can be usually done quickly and safely without opening up the Amp. Please observe standard safety measures and have a healthy respect for the high voltages.
  • Keep old Tubes for testing purposes such as temporarily replacing a suspect one.
  • Keep spares at the gig.
Ok I hope you picked up some useful info on the humble but fascinating Tube - For more detailed info try The Tube Amp Book by Tube Guru Aspen Pitman.
  • WARNING - NEVER work on any mains powered Guitar Amplifiers or Electrical Equipment unless you know exactly what you are doing! Even with the plug out of the socket, many appliances are capable of holding and producing LETHAL charges!





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