Myth: low-power high-efficiency


The past 6 - 8 months I have been living with very efficient speakers (~ 109dB/m/w) driven by low-power SET amps. The amps use 300B output tubes for about 7 wpc. On paper, this should be a match made in heaven. In fact, the combination is capable of wonderful nuance, subtley, harmonic richness, and tonality. It is really pleasing, especially on chamber and jazz music. Except for one thing - dynamic energy. I am not referring to loudness. It can deliver more undistorted volume than I care to listen to. I'm referring to immediacy, presence, power, and punch - the life of the music. If you go to the symphony, or live blues, than you know what I am talking about. Next week I'm taking delivery of a 90wpc PP amp, to audition in place of the SET. I need an amp that can maintain the purity of tone and harmonic texture of the SET, while delivering more power, to grab hold and take control the 15" bass driver in my horns.

I searched the archives, but have not found a similar post. Are there any other high-efficiency low-power people who moved to a higher power amp? Are you satisfied now?

Scott
skushino
Aside from its enveloping, holographic nature, this tube in certain amps will drive quite well, and give you considerably deeper and punchier bass than will the 2A3, especially when the amp is SS rectified.

Howard (Boa2), sounds like I got to try a pair of Welborne 300b amps someday :). Of course this is just your fault: You could have sent me the Welborne pair you tried a couple of months ago ;). Actually, why don't you just sent all your equipment north of the border, I always wanted to listen to a pair of KHorns driven by Wrights or a Mac.

Anyway, fun aside, maybe sometime down the line I will be able to listen to some 300b amps. Actually, I already found some Audiophiles here; I just need to convince them to bring over their amp for some extended listening sessions...

Otherwise, I am curious to see how the "switch" to the Mac amp works out for Scott (Skushino).

Best wishes,

Rene
Hey Scott. I have a speaker rated at 103 db. At least based on experience with my system, a high powered amp was not required to achieve the “dynamic energy” you refer to. I’ve gone from a high powered amp to a small SET amp. The first amp I used was a 160 watt OTL amp. A fantastic amp, but not the best match for my speakers as I was limited to use of 2 or 3 clicks total with my preamp’s volume control. I’ve tried some low powered amps with unsatisfactory results, until I used Art Audio’s PX-25, 6 watt stereo amp with fantastic results. Though, they really shined in the “dynamic energy” department after I inserted the new power cords and cables from Basis Audio. Note, that my subwoofers are powered by an amp driven by the output of the Art Audio; thus your mileage may differ.

I am unfamiliar with your speakers and associated gear. If others that have some of these components can achieve this dynamic energy, then I’d think it is not a component issue, it is a synergy issue. Certainly explore the use of other components with your speakers. But I would not limit this to say looking only at higher powered amps. In fact, like my OTLs, the sensitivity of some higher powered amps may make their use impractical with your speakers. Also, you may want to explore other cables/power cords, etc. I was shocked that changes in these products did significantly more than what I expected, which was a best a slight shift in various sonic attributes.
Keep in mind not all 300B amps/tubes and high efficiency speakers are created equal.
For amps, the output transformer and tube choice, parts choice and bias can make some difference.
For speakers, driver size to match cabinet design is extremely critical for high efficiency speakers regardless of the efficiency and response rating.

And then there is speaker placement, room acoustics issue.

Can't draw conclusion based on few experiment since some has succeed and some failed.