Valves - Matched Pairs

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Many amplifiers have a matched pair of output tubes. But what does this mean and why must they be ‘matched’?

In a guitar amplifier with two output valves, in simple terms one valve is pushing the speaker cone and one is pulling it.

With the same signal applied to each valve you can see that it’s important that each valve gives an identical amount of push or pull. If this was not the case, fidelity would be lost.

So you MUST replace both output tubes at the same time and you MUST buy a matched pair from a reputable dealer. At AmpValves we test all incoming stock and sort
into matched pairs (and quads).

A matched pair gives the same bias current under identical conditions of plate voltage and grid bias voltage.

Please note that valves (same make, same type) can differ wildly in their characteristics, hence this matching is required.

A new set of tubes can make a startling difference to your sound. Suddenly the amp sounds like it used to!

Here are some tips concerning valve replacement.

1. Keep a note of when you change your tubes, that way you’ll know when they need replacing.
2. Replace you tubes after approximately 1000 hours of actual playing. It doesn’t matter how old they are, it’s the number of hours they have been used which counts.
3. Never change just one output tube. They must always be changed as a set.
4. Always buy a matched set of output tubes. Either a matched pair or a matched quad. They have been matched to have the same gain and the same bias current.

We supply JJ tubes as they give a great tone at a sensible price. We also offer fast delivery so you can get your amp back up to spec as soon as possible.