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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

Showing 2 responses by mlsstl

mlsstl
1,378 posts
 
While there are no universal absolute rules, a common difference between tube amps and solid state is the manner in which they clip.

Many solid state amps clip harshly. The peaks above max output are flat-topped with a square-wave like edge. This generates a lot of higher order harmonic distortion that sounds harsh, metallic or edgy.

Tube amps generally have softer clipping when over driven. Since this is more pleasant sounding, it gives the impression of more power since you don't hit a brick wall.

Of course, there are a ton of variables to consider. The main ones are how loud you listen and the efficiency of your speakers. While tube amps have a devoted following they are not for everyone. Make sure you can audition an amp in your system before you commit.
mlsstl
1,378 posts
 
I was talking 'peak' power, not steady state.
Unfortunately I don't believe this term has a standard definition or measurement protocol. As such, the measurement varies widely between those manufacturers who even bother to publish a figure.

What's the duration of the "peak" - is it 1 millisecond, 100 ms, 1 second, 10 or something else? What's the distortion level permitted? What frequency (frequencies?) are used for measurement, or is pink or white noise used?

Depending on the games that are played, "peak power" can be 30% or 40% higher than RMS or it can appear as a multiple of even 5 or 6 times the steady-state power.

Given all of those variables, many people believe the only value a "peak power" measurement has is for the advertising and marketing department.
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