Tube Watts Vs. Solid-State Watts

This is a big topic of debate and discussion out there. It's generally accepted that a solid-state amp's wattage and loudness do not equate to a tube amp's wattage and loudness. Tube amps always sound significantly louder than solid-state amps in a watt-to-watt comparison. Most knowledgeable people will tell you a watt is a watt and there are many different factors involved that contribute to this. What we're really talking about here is "perceived loudness."

The generally accepted reason to this phenomenon is that tube amps can be pushed beyond their limits and still sound reasonably good, whereas solid-state amps will sound bad if pushed beyond their limits. If a tube amps is overdriven, it can introduce pleasing harmonics that make the tone sound fuller and louder. If a solid-state amp is overdriven, it will immediately sound harsh and unpleasing. It's why a solid-state amp typically needs to have a significant amount of wattage above a tube amp to be able to compete with the tube amp's output. In a way, that gives the solid state amp the clean headroom it needs to get loud without exceeding its limit.

Let's Conduct an Experiment

While the data from the sound level experiment below is by no means "official," it does give pretty good insight to the differences in the "perceived loudness" between tube amps and solid-state amps.

The experiment conducted measured the SPL in dB of three amplifiers:

• The Ampeg Portaflex 800: an 800W class-D solid-state bass amplifier
• The SonicTone BA-100: a 100W class-AB, fixed-biased all-tube bass amplifier
• The SonicTone BA-300: a 300W class-AB, fixed-biased all-tube bass amplifier

The control factors were as follows:

• All of the EQ controls were set to noon.
• The amps remained on channel 1. (The Ampeg does not have a 2nd channel.)
• The gain was set to 5.
• The amps were fed into a 4-ohm speaker load.

From there, the amps were measured with the master volume in three different positions while playing the open low-E string of a Fender Jazz Bass with passive pickups. The pattern played was a consistent running of an eighth note.

The Results