Amplifier Power Ratings: Solid State, Tubes, and the Bass Problem

I explore the relative merits of tube (valve) and solid state amplifiers and specifically their power ratings. One of the difficult things about assessing tube amps is understanding the power rating. If you're used to solid state amplifiers, then you're used to amps that deliver the rated power, or nearly so, over the entire audible range, from 20 Hz to 20 kHz, or whatever frequency range is reported in the amplifier specs. However, tube amps generally do not deliver anything close to their rated power at the lowest bass frequencies. Some amplifiers makers may report a so-called power bandwidth, which is usually a frequency range smaller than the range reported as the "frequency response," but the power bandwidth is usually measured at a level, typically 1 watt, much lower than the rated power. All this is not to say that one shouldn't buy a tube amp; I have several that bring me great enjoyment. I want to educate those considering tube amps about the meanings of power ratings and power bandwidths and that neither of these specs answers one of the most important questions that potential buyers have: How loudly will it play music and still sound good?

In the first part of the video, I talk about amplifiers and what I demand from mine. In the second part, I make detailed measurements of three different amplifiers: a solid state Nikko TRM-750, rated at 75 wpc into 4 ohms; a "flea-power," "hollow state" Magnavox 196-00 modified to be a DG-SE1 and with a measured power of 4.0 wpc into 4 ohms at 1 kHz; and an AMI-Rowe R-2620 with a measured power of 22 wpc into 8 ohms at 1 kHz. I measure the frequency response of the TRM-750 relative to 11 wpc at 1 kHz. Measurements of the tube amps focus on useable power at low frequencies. I also demonstrate each amp playing music, so the video features clips of several songs.