The most commonly asked questions about valves.
Q: What valves does my amp use?
A: You can find out exactly what valves your particular amp uses by clicking on the “Choose Your Amp” from the menu on the homepage. We have covered over 350 amps on the web site but if yours does not appear there, just drop us an email. Then you can use our build your own kit that will include all the valves you need.
Q: I’ve heard about this “bias” thingy – do I need to bias my valves?
A: Ideally yes but to do that you’d have to find a qualified amp technician near to you. Many guitarists don’t have access to this and cannot do it themselves, so they plug in the new valves and play. In the majority of valves we sell are usually installed by the owner without biasing. Biasing is really difficult particularly as some amps don’t even have “pots” that are adjustable so it’s not something you can do for yourself. (Also see answer below on “What is Bias Exactly?”).
Q: What is bias exactly?
A: Good question. It’s like setting the tick-over rate on the car. A power valve “idles” at a certain current. Adjusting the bias sets this current not too high and not too low. The good news is that there is quite a bit of tolerance which is why so many people do not bother to bias. Too hot and your valves will wear out a but more quickly, but you’ll get a fat sound. Too cool and the valves will last longer but the sound might sound a little thin in extreme settings.
Q: I’ve never changed valves on my amplifier before, is it easy?
A: Yes it really is. To remove a valve, steadily pull it. If it doesn’t come out give a VERY slight circular rocking motion and it will pop out. Note; I use the word very slight. If you are too violent with the valve you run the danger of bending the pins. To replace a valve, make sure the pins are correctly aligned with the socket (they only go in one way) then push it firmly home. The Health and Safety guy will also recommend that you hold the valves with a piece of cloth just in case the valve breaks and the cuts your hand.
Q: I’ve heard that brand ‘X’ valves give a superb sound. How do they compare with JJ valves?
A: Great question. There’s a huge amount of smoke and mirrors around valves with their ‘warm, dark sound and hints of blackberry on the nose’. In fact it is very hard to hear the difference between one good valve make and another. It is also impossible to test properly. Some guitarists seek the ‘holy grail’ valve because they think it will make them a better player. Some people just like to spend more money and are prone to advertising. We sell JJ which are really solid valves, giving awesome tone at a decent price.
Q: How can I tell if my pre-amp valves are blown?
A. Before we get into the theory, can I just say that every guitarist (especially a gigging guitarist) should have at least one spare pre-amp valve in their tool kit, carefully wrapped of course. Pre-amp valves are not made of concrete and so you should have at least one spare valve so you can quickly test when you have a problem or keep the band on stage when an amp goes at a gig.
Right, now on with the techy stuff. If one of your preamp valves is blown there are often a few tell tale signs:
- Visual Clues
Unfortunately, at first glance, a blown preamp tube will often look okay. Sometimes it may be more obvious because the valve is cracked or has a white film on the inside.
- Microphonic Valves
The easiest way to tell whether a valve is blown is when it goes “microphonic”. When this happens your amp gives off a high-pitched squeal when you turn up the volume. That will happen when the guitar is plugged in but also when it isn’t. You can test which tube has gone microphonic by gently tapping each valve with a pencil. Simply listen as you tap each one and the valve that is blown will sound very different from the others.
- Crackling Noises
Crackling, hissing and popping noises coming from your amp are a sign you have a blown preamp valve. However you need to eliminate the power valves in case they are the culprit. If you are hearing noise or crackling, you can rule out a power valve with this simple test. Gently tap on the power valves, one at a time using a pencil. They should not make any noise. If noise changes when you tap, this could mean you have a failing power valve. Always be ready to switch the amp off in case you have a failing valve and the tapping causes it to short out.
- Weak Signal
A blown pre-amp valve can cause your amp to produce a weak signal or lose all sound. A weak signal will diminish the amp’s volume and cause it to emit a low buzzing sound. A weak signal will eventually turn into a complete loss of sound.
- Lack of EQ Control
You may be surprised to know that the Pre-amp valves also control the EQ. If adjusting the EQ knobs on your guitar does not change the tone of your amp, you may well have a blown pre-amp tube.
- No Reverb
In older tube amp models, the reverb is also controlled by the pre-amp valves. So if your reverb begins to sound a bit odd, or you lose your reverb altogether, it could be a blown pre-amp valve.
Q: I’m looking for a certain sound on my amp (more bluesy, more bite, better low end, better top end, more headroom or whatever). Which valves would you recommend?
A: In our experience, changing valve manufacturer will not significantly alter the sound of your amplifier. You need to change amplifiers if you’re looking for a different sound.
Q. My amp is running too hot and sometimes blows a fuse.
My HT fuse blew on my Laney so I’m thinking that I may need a new set of output valves. I know that a blown fuse is the result of a fault not the cause and the replacement fuse hasn’t blown yet – but the amp seems to run very hot.
It’s not red plating but the rear panel is too hot to touch even with no signal. I can’t say whether it has always been like this and I gig virtually every weekend with it but I am a little concerned now. Would you know if they run hot naturally and if I need new ones would I need to re-bias? Any recommendations regarding replacements? ACDC, Sabbath type sound.
A. From what you have described I diagnose that the output valves are pulling too much bias current and that sometimes it just tips over enough to take out the HT fuse. You probably need a new set of output valves as they will have become worn with this excess current, but in this case you should then get the amp biased to make sure the current is correct.
Q. Is is easy to change the valves on my amplifier?
I am interesting in buying a replacement valve kit for my Laney VC15 as I have noticed a drop in performance after owning the amp for around nine years. I just wanted to enquire whether I would be able to simply replace the valves myself or whether any additional adjustments have to be made by an expert when changing valves.
A. Yes this is very straightforward job and you can easily do it yourself. There are some tips above on how to remove and replace your valves.
Q. Do 6V6’s sound different than 6L6’s? If so, in what way?
A. That’s a really great question. I wish I had a definitive answer. I can go into all the technical differences but they are small compared with the more important variations of:
1. The make of amp,
2. The speaker used,
3. The guitar itself,
4. The volume played,
5. The style of music played,
6. Most importantly, the “ideal” sound as determined by the guitarist.
Phew! Over the years I’ve had a pretty much 50/50 response from guitarists as to which they think is best. So it’s very much a personal preference. I’ve always taken the view that the manufacturer will have tried both types of valve and chosen the one that they deem to be the best sound. So when I get asked I always say “stick to what the manufacturer chose”. I do appreciate that some guitarists don’t like that sound and will change the valves to try and get the sound they are looking for.