Can tube amps give true high end bass?

Ulf, there's no way a tube amp will produce better bass than a solid-state amp. It's just the laws of physics. Specially, not a 40 Watt tube amp! What you are probably describing as "better bass" has to do with the coloration and second harmonic distortion that your tube amp is generating. Besides, the higher output impedance of tube amps create the conditions for slightly undamped resonance that adds to the "joy" factor. The end result is a warm, rich bass around the 40-200 Hz region to which you have become accustomed by now. The problem is, this bass is a distorted version of the original as stored in your recordings. Even worst, you probably are missing the very lowest bass frequencies that only a solid-state amp can produce, and which contribute greatly to the realism of your bass playback.

Regards,

T_bone, as amfibious said, I was talking about damping factor. This has been one of the big discussion themes since the 70's, but apparently it keeps being ignored by most audiophiles. Regardless, it will always be important because it predicts how good is the amp's ability to generate a bass fundamental without the speaker circuit altering its amplitude. Why this happens? The question has to do with the current vectors created in a third order (or bigger) circuit, such as that found in all speakers. It's pure math, but you can measure it and of course listen to it. It manifiests itself as a "boomy" bass at a certain favorite band of frequencies which depends on how the speaker was designed, and how well (or bad) the amp can control it.

Why do I think solid state amplifiers have the advantage? Transistors are low-voltage, high-current devices, whereas tubes are the opposite, i. e. high-voltage, low-current devices. Virtually all speakers in production today are low impedance transducers, varying from 8 ohms down to 1 ohm. THEY NEED CURRENT TO WORK! By nature, they work best with transistors due to their lower output impedances, and better damping factors. Besides, in order to equal a solid-state amplifier current capability, you would need a battery of 30 or 40 tubes in parallel (remember Julius-Futterman OTLs?). That's why most tube design depend on an output transformer in order to compensate for the disparity between tubes and speakers. However, IMHO transformers bring even worst evils than they cure. They introduce even more coloration, hysteresis distortion, they attenuate the lower bass, they introduce phase-shifting, etc. The situation is just hopeless.

I have no doubt that somebody will say "But I like the bass of my tube amplifiers better than a solid-state's. They really kick in ________ recording!". That's OK. It's just a personal preference, a very romantic one... ;)

Regards,

T_BONE: Another question back at you would be... how much tube power (watts vs output impedance) would one need to adequately power an 8ohm 96db woofer? say, the way a 40W solid state amp might...

Theoretically, Watts are exactly the same whether they come from a solid-state or a tube amp, so a 40 Watt tube should produce the same acoustic output as a 40 Watt SS amplifier. In practice, it depends on how conservative are both manufacturers on their power specs, but the differences should be negligible even for differences up to tens of percent (for example, a 40 W SS amp vs. a 30-60 W tube amp).

A more relevant factor is: How loud you like your music? With 40 Watts, you can have undistorted peak acoustic levels of about 112 dB at 1 meter with your speaker in anechoic conditions. Adding the other speaker and the room gain, you could easily surpass 120 dB peaks in your seat!! Ironically, at such loud levels a solid-state amplifier with better bass extension might stress your speakers and cause them to produce a phenomenon known as "Doppler distortion" (don't confuse this with another, notorious concept mentioned in the H-thread). In this case, a tube amplifier having weaker bass would produce a cleaner, more enjoyable sound, provoking the logical conclusion that the tube amp sounds "better" than the more accurate solid-state amp. The morals of the story is: If you want powerful low bass from your amplifier, first make sure your speakers can handle it!

Regards,