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help w/amp demo

On Friday, Sounds Real Audio of Golden, Colorado will be coming to my home to demo its Dehavilland 50a 40w tube amp w/my Aerial Model 9 speakers (full range, 90db sensitive, 4ohm). Given how good the 50a sounded at RMAF, I am very excited.

Nonetheless, while the 50a is designed to drive a bigger load than its specs would suggest, I am a little skeptical that it will be a good match w/the 9s (although I am hopeful). Thus, I have been doing a lot of reading on how to determine whether an amp is a good match w/a speaker and has enough power. In general, I think I have a handle on it.

One thing I don't understand is mention of a speaker making the amp "work too hard" as opposed to drving it w/"ease". I only understand that in the most general sense. My question is, how will I be able to tell if the amp is having to "work too hard" in driving my speakers? What should I look/listen for? Also, more generally, if people have ideas for how to decide if the amp is a good mate, I would love to hear them.

Thanks much.
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Showing 2 responses by almarg

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almarg
9,670 posts
 
Excellent suggestions by Tvad, as usual. The one thing I would add, with respect to your question about having enough power, is that a key variable is the dynamic range of the music you listen to.

I also have 90db speakers, in a 13 x 20 room, with the listening distance being about 9 feet. I am currently using an 80W tube amp (keep in mind that is only 3db more than 40W). On well recorded, minimally compressed, wide dynamic range classical symphonic music (which I listen to a lot) I find that the 80 watts is adequate, but just barely. A small nudge on the volume control above the position I normally set it to will result in slight but noticeable clipping.

On virtually all other kinds of music, listening at loud but sensible levels, the 80W is very easily adequate. A possible exception being things like some of the 1980's Sheffield Labs direct-to-disk LP's, some of which have dynamic range that is not likely to be encountered elsewhere. I haven't listened to those yet since I replaced my 200W solid state amplifier, which could handle them easily with the 90db speakers.

Best of luck!
-- Al
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almarg
9,670 posts
 
I get the impression that the dynamic limitations of a less powerful amp may be less of an issue for non-classical music, which is less dynamic?
Yes, with some isolated exceptions here and there, well recorded classical symphony orchestra will have much greater dynamic range, and therefore require greater amplifier power, than pretty much anything else (including other forms of classical music, as well as the types you mentioned).

A particularly dynamic recording of classical symphony can easily have occasional brief peaks that are 30 db or more greater in volume than soft passages (30 db being a factor of 1,000 in terms of watts). Since it is typically the lower volume levels within that range that comprise most of the music, the volume control will be turned up to a much higher position for that kind of music than for, say, rock, most of which is compressed such that its volume varies over a range of only a few db.

So the occasional brief peaks in a well-engineered symphonic recording will demand much more power from the amplifier than pretty much anything else.

Regards,
-- Al
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