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Re: Watts are watts

Speakers are driven by voltage. As such, the amp with the higher voltage potential will typically sound both cleaner and more powerful, so long as it has the necessary current required to sustain that voltage under any operating conditions. Given that tubes tend to run at a higher rail voltage, they exhibit traits that follow that supposition, but only up to a point. Most tubes aren't capable of a high current output, so that's where they run into trouble. On the other hand, SS amps typically run at a lower rail voltage, but are capable of passing quite a bit more current. This is why many tubed designs offer "finesse" whereas many SS designs offer "brute force".

With that info at hand, it would make sense that tubes would work best with a higher impedance speaker i.e. a load that didn't require much current. This would allow one to achieve all of the benefits of the design with very little of the drawbacks. At the same time, a well designed SS amp is at home with a wider variety of speakers, but the sound may not be as good at any given time as what one could achieve with a well designed tube amp. Then again, tubes tend to introduce a higher noise floor into the equation with increased levels of distortion, whereas SS amps are typically much quieter and can be more linear in operation. Each design approach has pro's and con's.

Having said that, the ultimate would be to have an amplifier that ran very high rail voltages with gobs of current, a low output impedance with a very high S/N ratio, very fast transient response with a very wide power bandwidth, circuitry that was naturally linear in operation so that there would be minimal need for negative feedback, was biased into Class A operation above the power levels required for the average listening session and had more than adequate amounts of heatsinking with proper ventilation. In most cases, 10 watts of Class A power would be adequate for a nominal 8 ohm load, but with a lower impedance or low sensitivity speaker, higher levels may be required. After that point, the amp could run in Class B mode for what should be several hundred watts per channel. Power should "double down" as impedance is halved, not only at the rated output, but at the point of clipping also. This means both a hefty power supply and a high current capacity output stage.

Extremely high efficiency designs ( 100+ dB's @ 1 watt @ 1 meter ) still require enough voltage and current to overcome thermal loading losses and reflected EMF, so the available power should be kept up as high as is possible while still being able to retain the aforementioned design goals.

With those variables in mind, an SS amp has more potential to achieve those results than a tubed design. At least, the tube designs using tubes that are currently being marketed for "audiophile" purposes. Why a manufacturer hasn't produced such a product is beyond me, although i do see some heading in that direction. Until we get to that point, not all amps or "watts" are created equally. That's because not all amps, tubed or ss, can deliver the same amount of power with the same amount of quality into all loads equally, nor do they recover from impedance changes in the load or dynamic changes in the signal in the same fashion. As mentioned above, an amp that is stable into any given load is what we are looking for, and even then, that stability has to be achieved with a high level of linearity and proper design traits. Too many engineers attempt to seek those traits, but utilize circuit design trickery ( gobs of feedback ) to cover up the lack of quality in the circuitry that they've devised to attempt such a task.

As such, pick your poison i.e. tubed or SS. Just make sure that the other components in your system and listening environment are the antidote for that poison, as a good system is one that balances the pro's and con's in equal manner. Otherwise, specific areas are highlighted and others are treated in a subtractive manner. While this type of system can be quite enjoyable to listen to, it is strictly a matter of personal preference and might not be to universal liking. Sean
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