The Tube Amplifier Solution

Tube amplifiers do some things that transistors can't, and vice versa. Before diving into that, allow me to take a little diversion.

Active speakers and Powered speakers are often confused.

  • Powered speakers have built-in amplifiers—they may or may not be active.
  • Active speakers make use of an active crossover (active x/o divides the frequency spectrum into individual bandwidths before amplification, then each bandwidth is sent to its own separate amp)—they may or may not be powered with built-in amps.

However, most active systems have built-in amps, which also makes them powered speakers, hence the confusion. What does this have to do with tubes? Powered speakers make the choice of amps impossible, and the use of tubes problematic. Vibrations inside the cabinet will microphone into the tubes. Not a good thing.

Today's renewed attention to analog has triggered a resurgence of interest in vacuum tubes and LPs. The aura surrounding these 19th century technologies has raised them to legendary status filled with nostalgia and wonder. The ritual involved with playing a 12 inch vinyl disk, from taking it out of the jacket, to slipping it from its sleeve, deftly holding it respectfully by the edges, placing it with conscientious deliberation on the turntable, then religiously cleaning before setting the stylus down with Zen-like precision into the first groove, is a finely honed sacred and transcendent ceremony. Tubophilia is no less encircled in a halo of angelic virtues worthy of banging the cymbal and strumming the harp, blowing the trumpet and sounding a chorus of cherubic voices in praise and worship. Alright, alright . . , let's come down from our 33 1/3 rpm spin induced high. A word of caution before we get too absorbed in the dizzying euphoria.

Tube amps have some limitations. It's well accepted that high efficiency, high impedance speakers are best, if not necessary, for tube amps. Not surprising when one considers the power requirements for reasonably realistic volume levels. The amount of power needed to avoid clipping and the subsequent high distortion may be shocking. Take, for instance, a speaker with a 102 dB sensitivity at 8 ohms. Very, very efficient indeed, and at a mere one watt from the amp, we can get a very loud 102 dB. (Measured at 1 meter with limited band pink noise or a 1 kHz sine wave.) But music isn't pink noise playing at a constant level. It rises and falls, sometimes greatly, particularly with percussion instruments that have striking transient spikes on the attack. These spikes can exceed 120 dB.

Let's use the piano, a percussion instrument, as an example. A loud passage may average in the mid to upper 90 dB range. This won't make a flea powered amp break a sweat. Spikes, on the other hand, can reach up to 120 dB or higher. Even a speaker with a sensitivity of 102 would need 10 watts to produce 112 dB, and 80 watts to handle a 121 dB peak without clipping. A speaker with a sensitivity of 92 (still better than average, most are under 90) would require a blistering 800 watts! And this example assumes 8 ohm impedance across the whole spectrum. How many people actually have 800 watts of transistor, or 80 watts of tube power (and 102 dB sensitivity speakers) to handle the situation? How many speakers never drop below 8 ohms? Not many. There's the rub. With either tubes or transistors there will be clipping, and with clipping we have gross audible distortion. But, and this is a big but, there is no doubt, the tube amp is going to sound better, especially over extended listening time. The tube amp is the winner. Its soft clipping, more gradual saturation, and quicker recovery rate is less harsh and easier on the ears. It's no wonder nearly 50% of audiophiles (see the surveys) have a preference for tubes. Should this seem like an exaggeration of power needs, read this link's Soft Sounds and Loud Sounds section.

This all assumes that clipping is inevitable. Unless we have prodigious amounts of amp power, it is. I have heard inadequate power problems time and again, almost exclusively with tube amps, and with very high efficiency speakers too. Careful listening will reveal this problem no matter how big, how expensive, or how sophisticated a system. (The example above, with the piano and 102 dB sensitivity speakers, was taken from a first hand experience of a very high-end system, $20k speakers, $22k 8 watt SET amp, that I auditioned in May 2009.) For any serious audiophile, this is unquestionably an unacceptable situation. It does not qualify as high fidelity. The solution?

An active system with three amps, each handling only a portion of the spectrum, each dealing with only a portion of the transients and the power required, is the most viable solution. The effect of using separate amps of reasonable power is not simply the sum of their outputs, it's effectively much greater than the sum. (And here is an instance when the word synergy might actually be appropriate. Read this link about : Actual vs Effective Power) By eliminating the clipping events, we've eliminated the only advantage of tubes. We've eliminated the high cost, the inefficiency, and the maintenance of tubes. We can quit fussing over amps, fussing over choices, and simplify our lives. Forget the system; listen to music.

Three short pages about : Valves vs Transistors & Harmonic & Intermodulation Distortion.& Output Impedence

And if you're still concerned about amplifier choices, read the following link. Masters on Audio : The Ongoing Debate about Amplifier "Sound"

An easy one page summary explaining valve and solid state electronics : Institute of Electrical & Electronics Engineers and The Audio Engineering Society Spell Out the Pros & Cons

Are you into fantasy or reality? Another Audiophile Debate

And about Analogue Warmth

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