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How often Do I need to replace my Valves ?

This is a question that is commonly asked about both preamp valves like the common 12AX7 ECC83 and also power valves like the EL34, 6l6GC, EL84.  The answer is not definitive but hopefully the following comments and things to listen out and look for may be of some assistance.

Valve technology has been around for many years and as most of us know they are consumable items so do need replacing from time to time in order to maintain that awesome and excellent valve tone from your amp.  There are many factors that can affect valve life and lifespan.  Useful life can vary considerably from one valve to another even valves that are the same brand and manufactured in the same batch.  You will often hear the comment "I have had my valves in for 20 years and they are still OK".  One of the problems is that most valves tend to age and die slowly so a low performing valve that has gone past its best is often overlooked.  It's only when they are replaced that the amp suddenly sounds different.  Brighter, Clearer, louder, deeper, more responsive etc.

So We have put together some factors that can accelerate valve life and also some things to listen out for and watch for as indicators that your valves could need replacing.  Hopefully you will find them useful.

Things that could potentially shorten valve life....

1 Excessive vibration or shock particularly when the valves are warm.

2 Using near maximum volumes and plenty of overdrive

3 Incorrect Bias settings for power valves

4 Low plate voltage

5 Excessive heater voltage and or plate voltage

6 Leaving valves powered up overnight or for extended periods of time.

Symptoms of Valve failure

1 White or milky top (this indicated vacuum is lost or soft)

2 Low volume

3 No transient attack, lack of depth in tone

4 Dull muddy sounding

5 Crackles and pops

6 Loud Hiss

7 Humming

It's important to note that on some new generation valve designs the heater glow can no longer be seen easily so heater glow not being visible is not necessarily and indication that a valve has failed.

As a general rule we advise that power valves should be replaced approximately after 300 hours of use and pre amp valves usually last at least twice that time.  But this is not a hard fast rule and as can be seen from the list above those times can vary considerably.  The best thing is to use your discernment.  

All the best from all at Voc Rock.

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