Can tube amps give true high end bass?

T bone, I think that Jmaldonado is talking about the damping factor. The damping factor refers to the amp's ability to control the motion of the driver. The DF is a ratio of the impedance of the speaker and the output impedance of the amplifier. Most SET amps have DF's around 10-20, whereas good SS amps have a DF of >100. A system with a poor DF will be unable to start and stop the woofer with any great degree of precision, so the woofer cone will continue to oscillate for a period of time. This gives "bloom" to the bass. You can get used to it ... in fact it's one of my guilty pleasures :)

The other thing to note is that speaker impedance curves are not linear and tend to drop around the bass region.

Most tube amps have output transformers which will help to lower the output impedance but output transformers can introduce their own sonic colourations as well.

Amfibius, Thank you very much for the explanation. I had ignored damping factor as a possible reason for this "resonance" because Jmaldonado talked about the amplifier rather than the amplifier/speaker interface. I realize that speaker impedance curves are (generally) not linear and for most speakers, will drop around the bass (except for my former ESLs) leading to the lowest DF at the lowest bass. I guess I automatically assume that people, especially those with low-power SETs, would seek appropriately matched speakers so they would get speakers with low DF requirements. My tube amps do quite well with my efficient and high impedance woofers, though my amps are "cursed" with very large OPTs and a surfeit of power and my speakers are designed to use low-power amps.

I wonder if that is the reason why we tube amp owners "miss" the lowest frequencies in the bass... I had thought that the main reason I was missing 12Hz was that my speakers reportedly only go down to 18Hz :^).

In any case, I would have thought that once one gets down to below 40Hz, it becomes much more an issue of the speaker's frequency curve than the amp's (if properly matched) and in the real world, anything below 60Hz and I expect that room loading/acoustics will make a mockery of the "flat frequency response curve" that an amp, tube or SS, produces.

NO they cannot on anything under 8 ohms

+++ No they cannot on anything under 8 ohms +++

Pray tell me why not?

The differencies are VERY noticeable even above 40 Hz.
I tried a system in my office:

1.PC as transport
2.Audio Note DAC 2.1 Signature
3.B&W 602 S3
4.Kimber VS8 speaker cable

Both with CAMBRIDGE AUDIO 640 V2 integrated SS amp,and with SET 300B MONOBLOCKS (2 x 9W).A/B testing for few hours.
Results - better than expected with every amp.BUT:

1. 300B monos had a better vocal,and treble and midrange alltogether.Which was expected,of course.
2. Bass - SS amp had more tight and more precise bass.Especially noticed in fast double-bass parts.More than depth,the bass SPEED was a problem for 300B.
Dynamic fast bass drum (double bass pedals) were significantly better with Cambridge amp.But these 300B monos
cuold be improved with better output transformer (which is the most important part for bass in SET amp).

This is why i plan to use SS monos on rear 12" woofer of my Silverline Sinfonia,as mentioned above in my post.Best of both worlds.