Tube Amp. Power ratings

Cincy_bob, 'chip amps' have been around in one form or another since the late 70's. The issue with them is that the form factor limits the amount of heat they can dissipate and the amount of current that they can pass. So you can damage them if you try to operate them on 4 ohm speakers. They require feedback for operation, a fundamental difference between them and tubes, which can be designed to operate without feedback.

Negative feedback enhances (slightly) high-order odd harmonic distortion, a form of distortion that the human ear can detect in levels of 100ths of a percent. This we hear as harshness or at best an unnatural sheen on top.

Thanks for the clarification, Mr. Karsten. One follow-up question: You mentioned in your post above that pairing a speaker intended for tubes with a transistor amplifier will result in tonal aberrations. Given that chip amps are generally not suited to driving difficult loads and seem best suited to pairing with speakers that were most likely designed around tube amplification, does this pose a quandary when trying to match these amps to speakers? In other words, does this leave you with one of two less than ideal choices: (1) You can pair the amps with speakers designed for solid state amplification (causing heat and reliability problems due to low impedances - not a very practical alternative) or, (2) You can pair the amps with speakers designed for tube amplification (causing tonal aberrations due to the solid state nature of the amplification).

Am I missing something here? Is there a type of speaker that is ideally suited to pairing with a chip amp?

Ralph,
Your comment would appear to make it uneqivocal, yet I must ask; does this hold true for tube amps with output transformers specifying 4 ohms?
John

>>In the case of tubes- *any* tube amp, the investment dollar in the amplifier will be best served by speakers that are at least 8 ohms rather than 4, all other things being equal, regardless of the technology of the tube amplifier.<<

Jamnesta, yes. The degradation in performance of any output transformer on its 4 ohm tap is audible and measurable. You can often loose an octave off of the bass end, and often too the actual power output drops as the transformer is less efficient.

Cincy_bob, the way out of the conundrum is to choose a speaker with a flat impedance curve. Such a speaker, if 8 ohms, will be about equally friendly to either technology.

Atmasphere, you seem pretty knowledgeable on this topic. I am not throwing out a trap or anything of the sort. I have tubed power amps (BAT VK-60 running at 120 wpc in mono). My speakers are Wilson Duettes connected to the 4-ohm tap and running pretty consistant at 4-ohms (as these speakers are known to do).

Both Wilson and BAT feel that this is a good match (discussed this with both company's prior to purchasing the amps). As you may (or may not) be aware, Wilson is demonstrating more with tubed amps and virtually all of the Wilson speakers (I believe) are 4-ohm speakers.

Again, this is not a trap and I am not contradicting you in any way.

But would you suggest when running a 4-ohm speaker with tubes it is better to connect to the 8-ohm tap? Connect to the 4-ohm tap? Interested in hearing yours and other's feedback on this question.

My Duettes seem to perform well (I have been extremely pleased with them and this combo, as well as with my MLevinson amp) and I am happy with the sound (although I have always run them with subs).