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Old 13th December 2006, 11:42 PM   #1
Klimon is offline Klimon  Belgium
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Default Tube-amp power issues

What is the term used for the 'more authoritative' (I'm looking for words) sound when comparing e.g. my 2watts el84 set with a 30watt el34 pp, speakers are about 90db/w?

Does this have something to do with headroom?

I've driven 90db/W speakers with my 2W amp for a while and although I enjoy listening and definitely prefer the low-powered amp (turned less than half-way up) over the 30watt beast, the latter does have the edge when it comes to dynamics (if that's the word)... I've experienced the same thing a couple of years ago with other 90db/w speakers, another 2w set and another el34 pp so it's definitely the result of the lack of power of the little sets. It doesn't have anything to do with bandwith either, the sets have lower f3.

Cheers -- Simon
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Old 14th December 2006, 04:05 AM   #2
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Simon, I think you have summed it up pretty well.. And FWIW I have noticed much the same thing comparing two amplifiers with much different power output capability on moderately efficient speakers, running at the same average spls and output power. (I've measured it) The differences seemed to be in the peak to average power ratio between the amplifiers, the higher powered amplifier sounded and measured less compressed.

Very small set amps need very, very efficient speakers to shine, at higher speaker efficiencies the smidge of dynamic compression I think I hear in some of my smaller amplifiers disappears.

My 45 amp seems to compress very gradually as it runs out of steam, and there is no obvious distortion, it just is not getting as loud as it should. Finally it hits a brick wall and the distortion becomes quite audible. It recovers quickly which makes it seem to play a lot louder subjectively than you would expect for its 1.6W. (Visible distortion on peaks above 1.6W)

My daily listener is a 300B amplifier which has enough power to not exhibit this effect at any reasonable listening level with the onkens.
That is until I build an even bigger SE amplifier to compare it to..
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Old 14th December 2006, 04:30 AM   #3
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It is called dynamic range.

However, no need for a wide dynamic range listening to some modern CDs because everything recorded on it is squized by compressors, but if you listen to a good symphonic orchestra you would love to feel the difference between mecco-piano and forte-fortissimo.
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Old 14th December 2006, 06:37 AM   #4
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As Wavebourn says, dynamic range (DR) is the name. With a symohony orchestra or a choir, for instance, a system with inadequate DR sounds throttled. That's why we need an amp/speaker combination to have a far higher output capability than we ever intend to use for normal listening levels, just so that transients are not choked off.
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Old 14th December 2006, 02:57 PM   #5
Klimon is offline Klimon  Belgium
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Thanks for your opinions - I'm glad I didn't simply get the answer: "you need atleast 10watts to drive 90db/w speakers"
Well - time for more efficient speakers!

Simon
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Old 14th December 2006, 06:20 PM   #6
Klimon is offline Klimon  Belgium
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Or a line-level filter would probably also bring an improvement. Say F3 at 80-100hz; relieving the tiny-amps of the lowest octaves. What do you think?

Simon
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Old 14th December 2006, 07:29 PM   #7
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Quote:
Originally posted by Klimon
Or a line-level filter would probably also bring an improvement. Say F3 at 80-100hz; relieving the tiny-amps of the lowest octaves. What do you think?

Simon
It depends on what do you call "improvement".

You may use also a compressor (for example, a bulb in parallel with a speaker and a photo resistor in parallel with a volume control pot output), in such case you save bass, but reduce dynamic range of music.
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Old 14th December 2006, 08:41 PM   #8
Klimon is offline Klimon  Belgium
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Let's say a passive first order filter @ 100hz (small cap between tube amp volume pot and driver stage) for the set amp + an active 24db/octave low-pass fed into an active subwoofer?

The first order high pass will only attenuate 9db @ 50hz and 15db @25hz but in terms of power I think it'll mean a >90% relieve for the tube-amp.

Simon
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Old 18th December 2006, 09:29 PM   #9
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Quote:
Originally posted by Wavebourn
It is called dynamic range.

However, no need for a wide dynamic range listening to some modern CDs because everything recorded on it is squized by compressors, but if you listen to a good symphonic orchestra you would love to feel the difference between mecco-piano and forte-fortissimo.

Ahh..I'll take you on this one.......Mike Oldfield (just an example) Amarok----- some decompression on this.....it will "push a 50Watt amp" from basic listening levels nicely up through the power midrange. It opens up the Fender beautifully...A 20watt HiFi amp will struggle. Not all CD's are fully level compressed. There is a warning label on this CD !

richj
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