2. amps-preamps
  3. 1267984978

Power output of tube amps compared to solid states

I'm having a hard time trying to figure out how tube amp power output relates to solid state power output. I've been looking at the classifieds for tube amps and I see lots of tube amps with 50w or 60w output, but nothing close to the 250w output typical of solid state amps.

So I have no idea what type of tube amp is required for my set up, right now I'm using totem forests with a required power rating of 150w-200w at 8ohms. The bass is so powerful on these that I have the sub crossover set to 40hz.

My question is, are tube amps so efficient that 50w from a tube sounds like 150w from a solid state? Or will 50w output from a tube severely limit how loud I can play my speakers? If so, are tubes usually meant to be driving super-high efficiency speakers?

I had previously tried a tube pre-amp with a solid state power amp (both musical fidelity) and didn't like the results because the imaging suffered greatly, even though the music sounded nicer from a distance. Now I want to try a solid state pre-amp (bryston) with a tube power amp (no idea which brand to look at), but I don't know how much power output I need or if it will even be possible with my speakers. Does anyone know what I would require?
acrossley
audiokinesis
2,751 posts
 
My understanding is that a woofer's electrical damping is described by the electrical Q (Qes) and the mechanical damping is described by the mechanical Q (Qms). The Qes value given in a spec sheet assumes a true voltage source amplifier, and in practice is raised by the amplifier's output impedance. I think the equation is Qes' = Qes x (Re+Rampout)/Re, where Re = the voice coil's DC resistance and Rampout = the amplifier's output impedance.

Much as I like prosound woofers, most of them have too much electrical damping (too low Qes) to give good bass extension with a low output impedance (high damping factor) amplifier. In other words, most prosound woofers are overdamped for home audio usage when used with solid state amps.

Duke
shadorne's avatar
Ag insider logo xs@2x
shadorne
7,477 posts
 
[/quote] In other words, most prosound woofers are overdamped for home audio usage when used with solid state amps. [/quote]

Good point - prosound woofers are often in a vice-like grip of the amplifier and excursions are tightly controlled and the bass is often tight and thin compared to the warmer and more extended sound of consumer designs. Partly this design approach helps protect the woofer from damaging over excursions.
pubul57
3,712 posts
 
What are the virtues of a DC-Coupled amplifier like the Atma-sphere?
kirkus
502 posts
 
Much as I like prosound woofers, most of them have too much electrical damping (too low Qes) to give good bass extension with a low output impedance (high damping factor) amplifier.
Excellent point - they also tend to have lower mechanical mass for sensitivity, and lower compliance for better power handling, resulting in a higher resonant frequency. The problem with increasing the amplifier source impedance for this type of driver (especially in a domestic application) is that while this raises the Q and the bass output, it leaves the resonant frequency unaffected . . . the result is then simply wooly, boomy mid-bass and no increase in bass extension.

An interesting exception is the JBL 2235/2245, which have mass-rings (weights) attached to the voice-coil former to both increase Q and to lower Fs. But this also makes them much more prone to over-excursion . . . so it's not uncommon for a reconer to remove the weights if there's a problem bottoming-out the voice-coil against the magnet, again raising Fs and lowering Qms in the process.
kirkus
502 posts
 
Pubul57, there's no shortage of material on the web that contains Atmasphere waxing lyrical about his approach to building amplifiers . . . I suggest you look at his website or peruse his posting history on Audiogon if you haven't caught it by now.
More to discover