18 Watt vs 50 Watt Tube Amp: Which One Do You Need?

An 18 watt tube amp breaks up earlier and sounds driven at lower volumes, while a 50 watt amp stays clean longer and gives you more headroom on a loud stage. The 50 watt is not close to three times as loud, though: the real difference is where the amp starts to distort and how the power section feels. Pick the one that matches the volume you actually play at most of the time.

How much louder is 50 watts than 18 watts?

Less than you might think. Our ears hear loudness on a logarithmic scale. You need roughly ten times the power to hear something as twice as loud. Going from 18 to 50 watts is under three times the power, which works out to about 4 to 5 dB. That is clearly louder, but not a different league.

What matters more in a room is the speaker. A sensitive speaker can add as much perceived volume as a big jump in amp power. So an 18 watt head into an efficient 2x12 can be loud enough for most rehearsals and many club gigs with a drummer.

Headroom: where the real difference is

Headroom is how far you can turn up before the amp starts to distort. This is where 18 and 50 watts really part ways.

• 18 watt: the power tubes start to saturate at a volume you can still use in a rehearsal room. You get compression, sag and that touch-sensitive breakup at a level that does not hurt.
• 50 watt: the clean sound holds up much longer. Your low end stays tight at high volume, and the amp keeps its punch when a band gets loud. Power tube drive only arrives at levels that are often too much for small venues.

If you get most of your gain from the preamp or from pedals, headroom is a good thing. If you love the sound of a cranked power section, a lower wattage gets you there sooner.

Power tubes and tone

Wattage usually goes together with a choice of power tubes, and that shapes the character too. Lower-power amps often use a pair of 6V6 tubes, which give a sweet, slightly compressed midrange and break up smoothly. Around 50 watts, a pair of EL34 tubes is a classic choice for British-style crunch, with a forward midrange and a bit more bite.

The Kool Ace shows this well because it comes in both versions. The 18 watt Ace runs on 2 x 6V6 and the 50 watt Ace on 2 x EL34. The 1984 follows the same split: 18 watts with 2 x 6V6, or 50 watts with 2 x EL34 / 6CA7. For more on how these tubes differ, read EL34 vs 6L6 vs 6V6.

What about playing at home?

A lot of people buy 18 watts because they play at home. That makes sense in principle, but an 18 watt tube amp at full power is still far too loud for a living room. Without a good way to turn down, both wattages end up being played with the master low, and neither sounds its best.

That is why a well-designed volume control in the power section matters more than the number on the back. The Ace has SVC (Seamless Volume Control), which lets you go from 0.1 watt bedroom levels up to the full 18 or 50 watts, without a power soak. The 1984 uses Loud and Louder attenuators for the same purpose. With controls like these, you can choose a 50 watt amp and still play quietly. See tube amp at low volume for more tips.

So which one should you choose?

A simple rule of thumb:

• Choose 18 watts if you play at home, in the studio or in smaller rooms, and you like the amp itself to do the breaking up. It is also the lighter amp to carry.
• Choose 50 watts if you play with a loud drummer, need clean headroom for a pedalboard, or want a tight, punchy low end at stage volume.

Weight counts too

Higher power means a bigger output transformer and power transformer, and that adds weight. On the Ace, the 18 watt head weighs 11.5 kg and the 50 watt head 15 kg. On the 1984, it is 14.5 kg against roughly 16 kg. If you carry your own gear to gigs or take public transport, a few kilos make a real difference over a year.

Unsure? Think about the loudest situation you play in regularly, not the one you dream of. Most guitarists who play small to medium venues are well served by either, as long as the amp has a good way to turn down. If you are also deciding on the format, our guide on amp head vs combo helps with the next step.

Try both versions of the same amp

The fairest comparison is the same circuit at two power levels. The Ace comes as an 18 or 50 watt head or combo, and the 1984 head as 18 or 50 watts. Both are hand-built in the Netherlands. If you want advice on which power level fits your music and your rooms, get in touch with Kool.