The most commonly asked questions about valves.
Q1: 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.
Q2: I’ve heard about this “bias” thingy – do I need to bias my valves?
A: Ideally yes. However, most of our customers don’t bother. When I say “most” I would guess 90% don’t. To be fair to them, although there is a recommended bias setting specified by the manufacturer, in reality, some guitarists will prefer their amps to run hotter or colder than the recommended setting. So we are not dealing with absolute numbers here. If you do decide you would like to bias your amp there are two routes. You can buy the equipment and a bias manual from us (check here to see if we have one for your model) and have a go yourself or you can take it to an amp technician. Biasing is easier with amps that have adjustable trim pots compared with those that have a resistor soldered in place. (Also see our answer below on “What is Bias Exactly?”).
Some amps are Cathode biased which means they do not need to biased. You can see a list of these amps here to see if this applies to you.
Q3: 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 bit 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. This is an important point because when you read on a forum that a particular set of valves, let’s say 6L6 power valves, sound like this on a particular amp, and break up at lets say volume 7, your set of so-called identical 6L6 valves may be running either hotter or colder and your amp may be biased completely differently. We have a more detailed blog on this subject here.
Q4: I live near Reading, can I collect from the warehouse?
A: Unfortunately the warehouse is not geared to accept customers or payment nor pull one order from the hundreds we send out each week. We do have a spare storage facility in Beaconsfield and if you drop us an email BEFORE you place your order we may be able to help with a collection. Once the order has been placed though we cannot intercept it.
Q5: 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 words “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 cuts your hand.
Q6: 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 valves which are really solid, premium quality valves giving awesome tone at a decent price.
Q7: 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 telltale 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.
Q8: 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 also have the problem that the amp was set up to take certain valves and changing to different ones will require an amp tech to make sure it can both cope and deliver the tone you want within the bias settings.
Q9. I have a Fender Deluxe Reverb and would like it to ‘break up’ sooner when cranked than the stock valves do at present. I have been told the 5881 valves will achieve this. Is this correct?
Q10. 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.
Q11. Is it easy to change the valves on my amplifier?
I am interested 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 inquire 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 a very straightforward job and you can easily do it yourself. There are some tips above on how to remove and replace your valves.
Q12. 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. The bias set up oh that amp for the particular power valves currently installed.
7. Most importantly, the “PERFECT” 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 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.
Q13. I want my amp to sound different.
I’m thinking of replacing my valves in my Fender Hot Rod Deville 4 x 10. Basically, I bought the wrong amp, I should have bought the Blues Deville. I’m trying to get the Hot Rod to sound like the Blues Deville, if possible. I’ve been told if I change the preamp valve in position V1 to a 12ay7, standard ecc83 V2 and a balanced ECC83 in V3 along with 2 x 6l6GC this can be achieved, any advice would be grateful. Also, would the bias be the same?
A. As a guitarist myself I will be blunt and honest. You will never get an amp to sound like a different amp by changing the valves. Once you have a particular sound in your head you will never be satisfied. That is why I have a house full of amps (all of which my partner says sound the same). It is true to say that swapping an ECC83 for an ECC81 will make a difference in the sense that it will reduce the power and that will impact to some extent on the tone – but in my opinion, it will never sound like a Blues Deville. Yes, you would also need to rebias if you change the power valves.
Q14. I have one amp that runs at 220 volts and one that runs at 120 volts. Do I need to specify the voltage when I order my valves?