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tubes vs. transistors,

Hi

It would be pretty hard to carry an argument of the function of one basic block (transistor or tube) without also considering what you’re doing with it.
While I agree some vacuum tubes have an inherently less audible distortion spectra per gain than a minimum component SS design, tube circuits generally use signal transformers.
One long careful look at output and signal transformers should leave one trying to find a way to live without them in the signal path. Looking at what they do with no romance, one is left saying ick.

In either SS or tube design, one can say the more negative feedback is used to reach the minimum desired spec, the more likely the amplifier is to misbehave under transient corrections.
Similarly, the more –fb is used to lower the intrinsic (open loop) output impedance to reach some minimum damping factor, the more likely it is to misbehave driving reactive a woofer.

Tubes have an inherent edge in bandwidth because they actually have an excessively wide (DC to RF) response which has to be limited. While a transistor has an open loop low pass corner decades lower in frequency so getting to 20KHz was the problem (all the –fb was used up just getting to 20KHz) in the beginning.

Lastly, one must keep in mind that the hifi industry as it is now has shrunk and bifurcated into group A that is focussed on selling slick looking Solid state equipment for as much as they can over cost to build and group B that would like to sell as much exotic gear as they can for as much over cost to build as possible.
Group A has hidden behind specifications and used them as a sales tool, Group B fully shuns engineering measurements and specifications saying they don’t describe what they hear.

Both groups have, in the face of decline, steadily honed a marketing strategy to appeal to the respective markets.
It reminds me of what a battle between Wallmart -VS- The New Age movement, might look like.
Curiously, by far the weakest link in the chain is the loudspeaker but SAF governed product boundaries prevents the mainstream from ever hearing what is possible.
Here is where the low efficiency tube folks (who often have larger, older, higher efficiency directional speaker designs) may have an edge, speakers of old, of a given power rating have much less power compression than a modern one of the same rating.
The reason was in the old days, they could not allow the coil to get hot as the glue melted easily. Nowadays a driver with the same rating would have a physically smaller motor system which will be much hotter at rated power.
All this is important because the speakers are a dynamic compressor ALL modern drivers begin to show power compression above between about 1/10 and 1/8 th rated power,
Dynamics are the heart of music where power compression is heart disease.
Hope that helps

Tom Danley



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