The humble Guitar Tube or Valve (UK) can
make or break your sound if you're using one of
these old-style design but wonderful sounding
amps.
It's well worth your while to find a good source of
manufacturer.
Lots of info and tips below ...
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Tubes or Valves as they're 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.
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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, 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:
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.
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!
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!
