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First Watts and high output amps

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Posted on April 16, 2014 at 13:26:15
fstein
Audiophile

Posts: 2996
Location: fstein
Joined: May 18, 2006
 This is a two part question
I have efficient speakers (Klipsch Cornwall 2's and 15inch Tannoys) and so the first watts really do count.
I listen to a lot of classical power music and wonder if my low to moderate output amps are missing something.
Would I gain anything by going to a high power amp, and are there any that excel in the first few watts?

 

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RE: First Watts and high output amps, posted on April 16, 2014 at 14:49:01
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 I would suggest listening to how loud a 500 Hz tone is on your system at 1 Watt. (This can be done in a variety of ways, the easiest being to produce a 60 Hz tone, measure that with your meter to get the voltage, then calculate the output based on your amp's gain. Work it out until you have 1W at 60Hz, then up the frequency to 500Hz)

Very few users will need more than a watt or two with high efficiency speakers.



 

RE: First Watts and high output amps, posted on April 16, 2014 at 15:16:32
Victor Khomenko
Manufacturer

Posts: 55319
Joined: April 5, 2000
 Well, I dunno... I am using 110dB speakers with 150W mono amps, and the combination sounds quite good.


 

RE: First Watts and high output amps, posted on April 16, 2014 at 17:15:49
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 Those Tanoys are fairly sensitive speakers, but how hard are they to drive? You need to look at the electrical load and phase angle diagrams to really know. Stereophile reviews generally show these. High impedance and flat is what you are looking for.

More and more people seem to be going to high power transistor amps with little or no NFB to capture the dynamics of "big and fast" symphonic music and raucous rock.

One of these amps, which isn't all that high-power, are the monos made by Crimson electronics.

 

RE: First Watts and high output amps, posted on April 16, 2014 at 20:40:54
hahax@verizon.net
Audiophile

Posts: 4310
Location: New Jersey
Joined: March 22, 2006
 First watts always count. Even an 85 db speaker is quite loud at 1 watt average level. Where you need lots more watts is occasional peaks that are very short in time but can be 30 or more db on dynamic recordings. Overloading an amp can be short term distortion or it can put it in oscillation for a noticeable period. Even a very efficient speaker can overload an amp of a very few watts.

 

RE: First Watts and high output amps, posted on April 17, 2014 at 00:37:14
KanedaK
Audiophile

Posts: 2519
Location: Brussels
Joined: April 27, 2010
 I've been using a 120 watts amp with my modded LaScalas for years, with great success.
Now using a lower power 18watts class A amplifier but I have to say the only thing that is better with the lower power amp is the bass: lower damping factor allows the overly dry souding hornloaded woofer to seemingly reach deeper and sound more "round".
For everything else the 120watt Technics sE-A5 was an amazing amp even at very low power (at comfortable volume levels the needle of the vu-meters barely reached 0,1watts).
Now I'm not quite sure all very powerful amp sound that good at very low output; you have to try...

 

the 'cleaner' the amp the better., posted on April 17, 2014 at 08:49:35
Ralph
Manufacturer

Posts: 4778
Location: Minnesota
Joined: April 24, 2002
 The problem you have is sorting out what is meant by 'clean'. You are correct that with high efficiency loudspeakers the first watt is important.

The issue is: what kind of amp will provide a good first 2 watts or a good first 10 watts while still doing justice to the first watt? With loudspeakers like this, a desirable trait in the amplifier is linear decreasing distortion as power output goes towards zero.

Now SETs accomplish that although they can't make power and bandwidth at the same time. But its a trick with any push-pull technology, as the presence of a phase splitter circuit often causes distortion to increase below a certain minimum power, depending on the size of the amp. This can be seen in the distortion figures whether tube or solid state.

I am of the opinion that loop negative feedback should be avoided in amplifiers that are used with higher efficiency loudspeakers on account of the more reactive qualities of the speaker (caused by the tighter gaps employed in the magnet structures of such speakers). The greater reactivity results in more back EMF. If that finds its way into the feedback loop of the amp that's not always a good thing- it can make the amp sound more shrill. Additionally, loop negative feedback will make any amplifier sound brighter due to the trace amounts of odd ordered harmonic distortion added by the effects of the feedback. So if the amplifier has no feedback, it cannot react in this fashion- then its a matter of making sure that the speaker has a high enough impedance that its load is not a problem for the amp. In this case its no worries.

Our ear/brain system uses odd ordered harmonics (5th, 7th and 9th) as loudness cues and also interprets their presence as brightness. The ear so sensitive to these harmonics that it can detect them even when they are difficult to measure (this is why some amps sound bright even though they have perfectly flat frequency response). So its best to avoid them in the design if possible.

For this reason I like amps that are fully differential and without a lot of gain. You don't need a lot of gain with more efficient speakers to begin with and the less gain, the less distortion. If the amplifier is fully differential, even ordered harmonics will be canceled at each stage of gain rather than compounded as the signal progresses through the circuit. The result is mostly the 3rd harmonic which is the only odd ordered harmonic that the ear regards as musical relative to the fundamental. If zero feedback exists, the 3rd harmonic will be at about the same levels as occurs in an SET (if we are talking about a tube amplifier). IOW, the THD will be considerably lower than an SET, offering greater transparency but without harshness and with considerably more power and bandwidth available. Such an amplifier will not have a dedicated 'phase splitter' circuit as there is no need.

An additional benefit of such an amplifier is that it can accept a balanced signal at its input, which has the possibility of reduced artifact from the interconnect cable.

 

RE: First Watts and high output amps, posted on April 17, 2014 at 10:24:39
wheezer
Audiophile

Posts: 4309
Joined: January 24, 2001
 For everything else the 120watt Technics sE-A5 was an amazing amp even at very low power

This is probably the result of the SE-A5 residing in Class A!
Class B transition can be sonically quite nasty.

 

RE: First Watts and high output amps, posted on April 17, 2014 at 10:53:24
Palustris
Audiophile

Posts: 2408
Location: Cape Cod
Joined: September 12, 2008
 I did something similar a couple of days ago when I needed to ensure two amps were at the exact same level. I used Stereophile test disk #2 track 1 in my CD player to generate a 1kHz tone and set the volume control on the amps to a typical (loud) listening level on my Altec A7 speakers. I then measured the output from the amps to make them exactly the same using a DVM. I chose 100mV as the level as it was not only a nice round number but coincided with the volume level at which I normally listen (based upon the position of the volume control). So that's .1V squared / 16 = .000625W!

BTW: these were SE 2A3 amps putting out almost 3W.

 

RE: First Watts and high output amps, posted on April 17, 2014 at 11:33:34
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 It's very important to remember that most meters are made to measure 60Hz, and frequencies far away from 60Hz will yield inaccurate measurements.

 

RE: First Watts and high output amps, posted on April 17, 2014 at 11:35:25
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 I didn't say it wouldn't sound good.

Your 110db speakers probably have 5 watts of power handling at frequencies below 50Hz. Just food for thought.

 

RE: First Watts and high output amps, posted on April 17, 2014 at 12:03:07
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 The associated design decisions that make the transition palatable are also themselves often nasty.

 

RE: First Watts and high output amps, posted on April 17, 2014 at 12:35:44
Palustris
Audiophile

Posts: 2408
Location: Cape Cod
Joined: September 12, 2008
 The Fluke 175 manual asserts 2% accuracy to 1kHz.

 

RE: First Watts and high output amps, posted on April 17, 2014 at 14:08:57
wheezer
Audiophile

Posts: 4309
Joined: January 24, 2001
 Very true.
I'll cut back on the volume before exposing my ears to it.

 

RE: the 'cleaner' the amp the better., posted on April 17, 2014 at 15:02:41
fstein
Audiophile

Posts: 2996
Location: fstein
Joined: May 18, 2006
 ? examples please?

 

RE: the 'cleaner' the amp the better., posted on April 17, 2014 at 15:13:59
Ralph
Manufacturer

Posts: 4778
Location: Minnesota
Joined: April 24, 2002
 Electra Print has a fully differential zero feedback amplifier. Seems to me that VAC does too as does BAT. Of course we do as well.

 

Some very good points Ralph. Thanks. (nt), posted on April 17, 2014 at 15:45:44
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 .
Have Fun and Enjoy the Music
"Still Working the Problem"

 

A friend checked output of sine wave (1KHz) versus control position, posted on April 21, 2014 at 00:58:13
FenderLover
 FWIW... 1 watt RMS (1kHz sine wave input) = about "12-O'clock" position on his Marantz integrated amp's dial. So, in terms of RMS value --- most music is played back in the 1st watt of power (RMS).

 

RE: A friend checked output of sine wave (1KHz) versus control position, posted on April 21, 2014 at 10:41:39
mcgjohn@yahoo.com
Industry Professional

Posts: 501
Location: Midwest
Joined: February 5, 2008
 By Missing something, you first need to define what it is you think you may be missing? Are you referring to dynamics, resolution, imaging, etc?

With your speakers, I would be more inclined to use a lower powered tube amp than I would solid state.

 

RE: A friend checked output of sine wave (1KHz) versus control position, posted on April 22, 2014 at 10:38:14
saki70
Audiophile

Posts: 274
Joined: February 2, 2006
 A lot of technical advice here that is probably very good , considering the contributors ! Most of it is way over my head .

I think that the more complicated the crossover network , the bigger the bass driver and the lower and more erratic the impedance curve the more power that you need to drive everything properly . I have always wondered
about a 1 or 2 watt amp having the ability to properly drive a 15" bass driver , regardless of the efficiency rating for the speaker .

Just my 2 cents worth .
saki70

 

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