Valves

CAN I REMOVE TWO VALVES FROM MY 100 WATT TO MAKE IT A 50 WATT?

We do not recommend the removal of any valves as a 100 watt amplifier is designed to work with four power valves. The removal of two valves can and will cause damage. One way to reduce the output of the amplifier will be to use a ‘power soak’. This gives you a lower physical output, allowing you to turn the amplifier higher to achieve the tone you are after.

Does fitting Mullard or other old valves make it more or less reliable, and would they make the amplifier sound better?

We recommend replacing your old valves with good quality new ones. Only use valves such as Mullard if you know and trust their history. If so, they should be no less reliable then a new valve. The tone or quality will vary from valve to valve. There is no guarantee when using old valves that they will sound any better then a new valve – it is down to individual taste. All valve replacement must be carried out by a qualified engineer.

Can I put different types of valves in my preamp to alter the tone or volume?

We recommend when replacing the preamp valves they are replaced with the same type and model. If you use a different type or model this can and will cause damage to the amp. All work of this nature must be carried out by a qualified engineer.

Can I put different types of power valves in my amplifier?

We recommend when replacing power valves they need to be replaced with the same type and model and they are matched. The amplifier will also need to be re- biased to match the new valves to the amplifier. All work of this nature must be carried out by a qualified engineer.

Can I mix the types/models of powers valves that I put in my amplifier to give a different sound?

We do not recommend mixing the power valves. They must all be the same type and model and matched. If different types of valves are fitted this can and will cause damage to your amplifier.

What do the different valves in my amplifier and combo do?

Most of our amplifiers and combos have a mixture of valves: some for preamp and some for the power amplifier. The number and type will vary from and amplifier to amplifier. The preamp valves take the small guitar signal and amplify it and alter it both in gain and tone and feed the larger signal to drive the power valves. The power valves then feed the larger signal to drive the speaker through the output transformer. Some of our transistor units, for example the AVT Series, have an ECC83 valve in the preamp to add tone and colour to the signal.

Does it matter if my valves are glowing blue/purple?

This does not necessarily indicate a fault with the valves or the amplifier or combo. But we would recommend that you have it checked out by a qualified engineer.

What is the lifespan of a valve and when and how should I change them?

A valve does not have a set life span. We normally recommend the power valves are replaced every eighteen months to two years. Preamp valves should be changed approximately every four years. When having your power valves replaced we recommend these are matched and the amplifier is re-biased. Regarding the preamp valves, these can be replaced individually as preamp valves do not need biasing when replaced. All work of this nature must be carried out by a qualified engineer.

Do I need to change all my power valves at the same time, and do I have to re-bias the amplifier?

We recommend all power valves are replaced at the same time and you use matched valves. The amplifier will need to be re-biased to match your new valves. All work of this nature must be carried out by a qualified engineer.

What is meant by the term bias?

When replacing power valves, to ensure they work correctly, giving the required sound and ensure a long working life, we recommend the amplifier is re-biased. If the bias is not set every time the power valves are replaced this can and will cause damage to the valves and amplifier. All work of this nature must be carried out by a qualified engineer.

What is the difference between a 12AX7 and an ECC83?

The term 12AX7 is the American model number for the ECC83.

What is the difference between a 6L6 and a 5881?

The 5881 is the same type of valve as the 6L6 but with slightly higher output. The bias on the amplifier will need to be set depending whether you are using 5881 or 6L6 valves. All work of this nature must be carried out by a qualified engineer.

Can I mix different makes of EL34 power valves in my amplifier or combo, and will this improve or alter my sound?

We recommend when replacing your EL34 power valves you use the same type and make and ensure the valves are matched together. The amplifier will need to be biased for the new valves. If you mix makes this can and will damage your amplifier or combo. All work of this nature must be carried out by a qualified engineer.

If I have the bias altered does this improve or alter the sound of my amplifier or combo and will it effect how long the valves will last?

Setting the bias value too high or too low will alter the sound of the amplifier and shorten the life of your power valves, and could damage the amplifier or combo.

If I use a power soak will this affect the life of my power valves?

When using a power soak with a valve amplifier or combo, because you tend to drive the amplifier harder and louder, the life expectancy of the power valves could be shortened.