Tube vs Tran

Back to the original question of why would anyone ever buy SS when tube "sound so good". Many speakers benefit from the extremely low impedance at SS amps which causes a high damping factor.

Basically the damping factor rates the amps ability to control the physical ringing of speakers after a note has sounded. If you switch out amps while listening to a passage with lots of bass content, it'll be very obvious as you move from a low damping factor to a high damping factor or vice versa.

Vienna Acoustics, DALI and Sonus Faber are examples of speakers that are really designed to work best with a high damping factor and relatively high power.

Tube amps are sometimes described as having "woolly bass." This is probably because they were paired with a speaker that needed a much higher damping factor. Relative to tubes, SS amps tend to have higher damping factors, but they're not all equal. The Jeff Rowland 501 monoblocks have a damping factor of like 1000 into an 8 ohm speaker. That's very high (and you hear it) but a damping factor of 100 or 50 isn't unusual for SS amps.

Generally, if you hear a speaker with a woolly, ringing bass, it'll very likely benefit from being driven by a SS amp with a high damping factor.

Dave

Dave, I respectfully disagree. The idea of damping factor is mostly mythology. If you hear a differece between an amp with a 'damping factor' of 1000 and one with 50, its likely due to other things than 'damping factor'. More likely the differences you hear are due to the amounts of negative feedback required to make a 'damping factor' that high.

One would be severely challenged to actually be able to define a sonic artifact and point to 'damping factor' as its cause. Audio signals require that the power energizing the speaker diaphragm not only carry it to the limit of the signal's excursion, but also back again to zero. There are no audio signals that stop at the peak of the waveform and fall to zero instantaneously- even synthesizers don't do that.

This is not to say that the output impedance of the amplifier does not have an effect on the sound (damping factor is an expression of output impedance, BTW). For more on that see
http://www.atma-sphere.com/papers/paradigm_paper2.html

Tube amplifiers can have excellent bass (given an appropriate load). The 'wooly' term at best is innuendo without a being a true statement of merit. There are tube amplifiers that can reproduce a 20Hz squarewave as well as transistor amps can. In the past there were older, lessor designs, but that says nothing about what is possible today.

Thanks all for a lot of great information. I AM NOT going to use a sub and have never really liked the idea or cared for sub in TWO channel system. With proper speaker, I don't think it is needed.
Rick

Here's a link about damping factors:

See http://en.wikipedia.org/wiki/Damping_factor

Measured square waves are not relevant to damping because of the interaction of the speaker and cable is also part of the equation.

Dave

I agree that damping factor has some effect on the poor bass of most tube amps. But wooly bass can mostly attributed to the hundeds of feet of wire in the output transformer. This is not always the case but the main reason.