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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
marakanetz's avatar
marakanetz
5,473 posts
 
Atmasphere,
my due respect to your OTLs, they are money-no-object electronics for whoever can afford to spend extra $$$ for nearly twice larger amount of tubes per channel for the same desired output power vs. an amp with output transformer.

speaking of power compare in plain English, 100Wpc amp wouldn't 'reach' to 12" woofer... you wouldn't even see it's moving unless you crank the volume levels high; while 250Wpc amp would move the 12" woofer at the same sound pressure levels... so 4db also has diversified meaning towards full range.
atmasphere's avatar
atmasphere
11,807 posts
 
Marakanetz, not to be on your case or anything but while we do go for as much performance as possible at the same time we take advantage of the vintage look to keep the overall cost down, making our amps affordable against similarly-powered tube amps.

The idea that larger woofers are harder to control is pure mythology and a common one at that. My speakers at home have dual 15" woofers per side and our little S-30 can put plenty of excursion on them.

The amount of excursion a speaker has can be extremely variable as all speakers have different damping requirements. IOW it is not the case that the higher the damping factor the better- in fact there are no known examples of any speaker needed more than a damping factor of 20:1, yet there are cases of speakers that need damping factors as little as 0.1:1 (usually these are designs intended for open baffle).

If the amplifier under-damps the speaker, you actually get excessive excursion rather than too little, and vice versa if the the speaker is over-damped.
dividebytube
50 posts
 
Rrog -

I was talking 'peak' power, not steady state.

http://www.the-planet.org/dynaco/Amplifier/Mark%20III%20review.pdf

see the above for some measured performance.
mlsstl
1,436 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.
pubul57
3,712 posts
 
I remember hear a 30 watt tube amp "versus" a 250 watt SS amp at a Stereophile show, simply to see if people coult tell which was playing in an A/B demo. I don't think the speakers were particularly high efficiency, but the difference in power was not in the least bit noticeable at fairly loud show room conditions - and yes, it was fairly easy to pick the tube amp.
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