tube watts vs solid state watts

Actually, most tube amps run into difficulty driving low impedance loads and put out less power at 4 and 2 ohms than most equivalent solid-state designs (many of which double power into 4 ohms and then double again into 2 ohms). So if you have a well designed ss amp rated at 50Wpc into 8 ohms it could put out 100Wpc into 4ohms and up to 200Wpc into 2ohms. A typical tube amp rated at 50Wpc will put out nearly the same 50Wpc at 4ohms and much less power (maybe 25 watts) at 2 ohms. That said, a few tube amps are specifically designed to drive low-impedance loads more efficiently. I believe that VTL has a few models optimized to drive 4-ohm loads.

Additionally, tube amps traditionally have terrible damping factors which is why their bass is loose and indistinct compared to decent solid-state.

The clipping characteristics of tube and ss amps do differ, and tubes do sound less harsh and do less harm to tweeters. However, except in Pro sound applications, anyone who, on a regular basis, drives their amps into clipping is simply using the wrong amp. Solid state amps can have circuitry that detects when clipping is on the verge of happening, and prevents it by a gain reduction. Of course this is compression, but at extreme volume level it is scarcely noticeable, and sure is better than clipping. Pro sound amps are most likely to have this feature, because these amps are often used right up to their power ratings, and with live sources that can not be preauditioned to set gain. I am using CarverPro digital amps, 600 wpc at 4 ohms, that have clip detection, and I have this feature switched on. Much to my surprise I discovered that my Maggie 1.6 speakers, 4 ohms, can trip the clip limiter feature if I play certain music at too high a volume level.

Jax2

"d" minor - saddest of all keys.

:-)

interesting paper about tubes vs transistors here

http://www.milbert.com/tstxt.htm

Larry

The "paper" by Russel Hamm appears to be a presentation at a session of the AES nearly 13 years ago. Such presentations typically are not peer reviewed. The questions following a presentation can be a form of peer review. The presenter appears to have connections with a manufacturer of tube amplifiers. Were it a peer reviewed article, I suspect the premise of the study, driving equipment beyond its operating range, might have been questioned and caveates added to the generalizations. Furthermore the confusion of the "loudness" of a trumpet with its SPL should have been corrected. Finally, why study the attacks of synthesized instruments rather than the instruments themselves?

Bottom line: This is not a peer reviewed article, but a presentation in front of a session of a technical society by someone with commercial connections that give the appearnce of a conflict of interest. I have seen presentations where there were only a few people in the audience, other presentations where the questions were embarassing and/or contentious -- I chaired a session that had one such presentation. As chairman, you're faced with a dilemma: Do you hold to schedule for the convenience of those who jump from session to session or do you permit extended discussion that is the reason for live presentations? You'll make enemies in either case.

db