Is a Tube Amp Capable of High Current?

I thought I could get by under similar circumstances with a fairly high power stereo tube amp driving a pair of speakers with 81 db efficiency and a 3 ohm load. It was great if the music was quiet or solo acoustic but it didn't work worth a darn on anything requiring more "ooomph" such as symphonic. I didn't want to get rid of my tubes and was able to drive the mids/tweets with tubes and SS on the woofer... This happened to work great in my case and I got the best of both worlds but it is often difficult to get tubes and SS to mate well.

While I don't have any experience with your particular amp, I can state with confidence that the Wolcott Presence will meet the match - for whatever that is worth. -aj

Tube amps (except OTL types) use an output matching transformer. This transformer presents (relatively) fixed impedance (usually settable to 4, 8 or 16 ohms) to the speakers. The Matching Theorem (see any good EE circuits textbook) says that a source (i.e. amp) with fixed output impedance supplies maximum power when the load (i.e. speaker) has the same impedance.

Thus tube amps normally don't do well with demanding loads with impedances that vary across the audio spectrum. For example, when the speaker is attached to the 4 ohm tap on the amp, it gets maximum power when its impedance is also 4 ohms. Most speaker impedances vary across the audio spectrum, so power delivered to the speaker also varies with frequency. This effect is partly responsible for some of the tube sound.

Another way to look at it is that the inherent impedance of the transformer limits the current.

We can turn the matching theorum around, and ask what source (amp) output impedance delivers the most power to a given load (speaker). In this case, the lower the source impedance, the more power you get into a given load.

Transistor amps normaly don't have output transformers (there are a few exceptions). They tend to have very low output impedances. Many, (especially those built with massive power supplies and running class A) have output impedance much less than an ohm and can deliver large amounts of current into low impedance loads.

So if you need lots of current, solid state is the way to go. You can get there with tubes, but you need a lot of them, and massive (expensive) output transformers to go with them. They still supply maximum power only at the selected output impedance, though.

I don't think a 6 Ohm load will require that much current. 84 db's will require power though. A high power tube amp should fit the bill. Though a high power tube amp usually comes with a high bill. I'm not familiar with your speakers but a high power VTL should fit the numbers. Of course fitting the numbers doesn't mean it will float your boat sonicaly.

I second Angela100's suggestion of Wolcott amps (disclaimer - I'm a Wolcott owner & dealer). No, they won't double their power output going from 8 ohms to 4 ohms, and again into 2 ohms, like a beefy high-current solid state amp will. But, they will deliver their rated power into a 1.7 ohm load, which is pretty darn good for a tube amp. Especially for a tube amp that uses EL34 tubes, which are traditionally noted for their midrange performance, rather than their stability into difficult loads. But Wolcotts are the amplifier of choice of many Sound Lab owners, and Sound Labs are a difficult speaker to drive.

A feature of the Wolcotts that is quite welcome with demanding loudspeakers is the adjustable output impedance control, which allows the user to fine-tune the amplifier/speaker interface.

I'd be happy to answer any specific questions you might have.