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 600 amps on our web site but if yours does not appear there, just drop us an email. 

Q2: I’ve heard about this “bias” thingy – do I need to bias my valves?

A: Ideally yes. We will always tell you to bias them every time. That’s because if there is a problem and the valves “redplate” we could be held liable for not giving you good advice. However, as you will have seen on the forums, most amp owners don’t bother. When I say “most” I would guess as many as 90% don’t.

To be fair to them, although there is a recommended bias setting specified by the manufacturer, in reality, some guitarists will actually 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 testing 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. If you do go to an amp tech you will have the peace of mind that it is correctly set up and if you need it tweaked to be hotter or colder than the recommended setting this will be done for you.

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. There aren’t many in this category but you might be lucky – or you bought that amp for that reason.

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 let’s 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: “Biasing amplifiers – what’s involved?”

We also have a blog dedicated to “Cathode Bias – What is it exactly” that you can read 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 are they able to 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 your 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.

Warning: Do remember that guitar amplifiers carry very high voltages even after they have been switched off so be sensible and don’t go poking around in places that don’t concern you.

Q6: I’ve heard that brand ‘X’ valves give a superb sound. How do they compare with JJ valves?

A: Great question.

If you have visited a few forums you quickly realise that if you ask 5 guitarists which valves are best you get six different answers. There’s a very simple reason for that and it’s called ….. the “variables”.
If you take five identical amps straight off the production line and compare them brand new, they all sound different. That’s because even at that point there are differences in the manufacturing processes. Also, the brand new valves inside vary massively and the setups also vary massively.
Now send those amps out into the market place. Let five different guitarists plug them in. They all use different strings, they have different settings on both their guitars and their amps, they use leads that cost from £5 to £55, they play differs styles of music, at different volumes, in different rooms with massively different acoustics …..  they are even playing different guitars.

There’s more but I think you get the idea.
So the answer is it’s a bit like choosing a girlfriend – play around and find out what you like. (Apparently, that’s not the correct PC company line here but it’s the easiest way to explain the concept that we all like different things).

Q7: Where does the “Balanced Valve” go?

The balanced valve goes in the final preamp position. So that means it is nearly always the one furthest from your input jack where you plug your guitar in.

the balanced valve is used for the phase splitter so works in a totally different way to the other preamp valves.

It should go furthest from the input jack and closest to the power valve section.

The good news is, if you do accidentally get them mixed up it won’t do any harm to the amp. We mark the box they come in as “balanced’ and we also put a small letter “B” on the top of the valve using a black permanent marker.

Q8: 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 quickly 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.

Q9: 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.

The forums are full of opinions and, as you will see, if you get 30 comments you will get 29 different opinions. The reason there are so many opinions is simple –  there are so many variables.

  • No two amps sound the same.
  • No two guitars sound the same. Even two identical guitars made the same week will sound different.
  • All guitarists play in a different style.
  • We all have a different idea in our head of what sound is “best”.
  • You play rock and I play country.
  • You use different strings to me.
  • Your guitar is set up differently to mine.
  • I have a brand new £60 lead – yours is a tatty free one the shop gave you that is adding more noise than you could ever imagine.
  • You have the tone set low and the volume high. I have the bass dialled in and low volume because of the neighbours.

The list is endless – which is why the discussions are futile. You need to change your amplifier if you’re looking for a different sound – which is the reason I own so many amplifiers.

Q10. 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?

A. We have many customers who order 5881 power valves (and ECC81 preamp valves instead of ECC83 preamp valves) in order to achieve different gain or break up points along the lines you suggest. However, this is very subjective. It depends on the guitar used and the style of play,  and the output level of the valves. All power valves run are at different levels which is why you always have to buy matched versions. Naturally, if you have a set of power valves rated at a different level to another “identical” set you get a different break-up point.

Then there is the issue of the bias of the amp. This will also will affect the break-up point of the valves you use. This is why there are so many conflicting comments on the forums. As a result of so many varying factors affecting the break-up point, this is not an area we feel comfortable giving advice on. There are plenty of forums on the internet which will be able to help you – but as you will see, there are as many different opinions as there are comments.

Q11. 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. 

Q12. Is it easy to change the valves on my amplifier?

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.

Q13. 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.

Q14. 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.

Q15. 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?

A. I’m assuming you are talking about MAINS INPUT voltage for your two amps? E.g. one is UK voltage and one is USA voltage. If that is the case then no, you don’t need to make any changes and your valves will work perfectly with either amp. Your amps have different mains transformers to handle the two different input voltages, but they produce identical OUTPUT voltages and so you can use the same valves.

Q16. I have a noisy scratchy volume pot. Will a contact spray solve the problem?

A. Yes, you can use a contact spray and we estimate you have a 50/50 chance of this curing the problem without removing the chassis. Those are pretty reasonable odds considering the small outlay. The product we recommend is Caig Deoxit D5. We have found this to be the best product available. It is not the cheapest but well worth the extra money. The 40g can is about £13.00 at the time of writing.

Here’s how you do it. Put the amp on its back so the pots are pointing upwards. Remove the knobs on any of the pots you want to clean. Now spray the DeOxit onto the shaft, close to where it enters the chassis. The plan is that enough runs down the shaft and into the pot body. Turn the pot backwards and forwards a few times. We reckon that on average 50% of the time this will work. 50% of the time you have to take the chassis out and try to get the nozzle into the pot.

To find out more about scratchy sounding pots click here

Q17. My amp keeps blowing fuses.

There could be many reasons for this but If your amp keeps blowing fuses the starting point is to replace the rectifier valve (if it uses one). Amp owners often change their preamp and power valves but forget about the rectifier valve. The first job is to swap that out.

Q18. My amp is starting to make a bit of noise (crackling, popping, hum etc). Is it likely to be the valves?

It’s always hard to diagnose an amp fault without looking at it but the first sign that your valves are getting worn is a noisy amp. Changing the valves is always a good starting point as they are usually the culprit when you get this kind of problem. You can do it yourself very easily and you won’t need to take it to an amp tech if this proves to fix the problem. If it doesn’t at least you have removed one of the potential problems and saved yourself the labour fees and valve markup fees at the same time.