2. tech-talk
  3. 132841-3105

Which watts are the right watts in SS amps?

Hello Sports Fans!

More than a few people over the years on these pages have said only those SS amps which double down in output power as impedance drops are truly special or worthy amps. Eg., 200 @ 8ohms; 400 @ 4 ohms; 800 @ 2 ohms; etc.

Not every SS amp made does this trick. Some very expensive ones don’t quite get to twice their 8 ohm rated power when impedance halves to four ohms. BAT, darTZeel, Wells, and Ypsalon to name just a few.

An amps ‘‘soul’’ or it’s ‘voice’ is the main reason why I would opt in on choosing an amp initially and keeping it. Simultaneously , I’d consider its power and the demands of what ever speakers may be intended to be run with it or them.

I’ve heard, 80% of the music we are listening to is made in the first 20wpc! I’m sure there’s some wisdom in there somewhere as many SS amps running AB, are biased to class A Only for a small portion of the total output EX. 10 – 60 wpc of 150 or 250 wpc.

After all, any amps true output levels are a complete mystery when anyone is listening to music anyhow.

I suspect, not being able to actually measure true power consumption, the vast majority of listening sessions revolve around 60wpc or so being at hand with traditional modern reasonably efficient speakers.

Sure, there are those speakers which don’t fit into the traditional loudspeaker power needs mold such as panels or electrostats, and this ain’t about them.

The possibility of clipping a driver is about the only facet in amp to speaker matching which gives a person pause while pondering this or that amplifier.

I feel there is more to how good an amp is than its ability tou double output power with 50% drops in speaker impedance.

However, speakers are demanding more power lately. Many are coming out of the gates with 4 ohm ‘nominal’ IMPs which lower with fluctuations in frequency. Add in larger motors on larger drivers, multiple driver arrays, and on paper these SOTA speakers appear to need more power.

IMHO It is this note which introduces great concern.

I’ve read every article I can find on Vienna Acoustics Music. Each one says give them lots of watts for them to excel.

Many times good sounding speakers I’ve owned sounded better with more power, albeit from arguably a better amp.

I tend to believe having more than an adequate amount of cap power is indeed integral. … naturally the size and type of transformers in play possess a strong vote for an amps ability to successfully mate with speakers.

Controlling a driver’s ability to stop and restart is as well a key to great sound and only strong amplifiers can manage this feat. Usually this gets attributed to ‘damping’ factor, but damping as I read it is more a shadow than a tangible real world figure as it depends on numerous factors. Speaker cable length alone can alter damping factors.

A very good argument exists about those mega watt amps voices. Each 500 or 600 wpc amp or amps, I’ve heard have had stellar voices too, not merely more watts.

So is it predominately these mega watt power house amps souls or their capacities that fuels the speakers presentation?

Would you buy an ‘uber expensive’ amp based more on its voice or soul, than on its ability to output loads of watts, even if you feel the amp may be somewhat under powered for the application?

Choosing this latter option also saves one money as the more powerful amps do cost more than their lower outputting siblings.

Please, share your experiences if possible.

Tanks muchly!

blindjim
114 responses Add your response
shadorne's avatar
Ag insider logo xs@2x
shadorne
7,477 posts
 
This article explains why some very powerful amps sound terrible at low levels.

https://benchmarkmedia.com/blogs/application_notes/power-amplifiers-the-importance-of-the-first-watt

My power amp has a sliding bias so it stays pure class A up to 2/3 power...that is what ATC chose to do with their active speaker electronics.

I dont recall what Bryston does but big poweful class AB amps that dont have specific solutions to this problem need to be serviced often to ensure zero crossing distortion remsins as low as possble.
willemj
1,036 posts
 
Well, it is a free world, fortunately. However, for me it is not the job of my gear to change the sound of the music - I am not the artist. What I want is simply what Quad once called ’the closest approximation to the original sound’. I accept that that is a very modest brief, and at least for the electronics part of the chain easily achieved (witness the Yamaha that I linked to). With speakers and room interaction it is a different story, unfortunately.
Shaping the sound to your liking can be done much more cheaply than by buying exotic gear and expensive cables - just use a graphic equalizer, or if you want to get fancy, use one of the modern plugins for recording studios: vinyl, a Studer tape machine or tubes on the cheap and without the hassle.
geoffkait's avatar
geoffkait
23,365 posts
 
Dynamic range overrides frequency response any day of the week. Besides unless you’re prepared to pony up lots of cash on room acoustics you will never get flat frequency response on any room.
erik_squires
16,056 posts
 
@willemj wrote:

A flat frequency response is crucial for a natural representation of the music. You don’t want the system to artificially boost or depress certain frequencies, and hence change the sound from what it was.

I think you should buy what you like, and whether it is perfectly realistic or not is not among my first purchasing priorities. I spend money to make myself happy, not reviewers and not any of the 4 measuring microphones I own. :)

Having said this, I think discussions about technology, pros/cons are always fun and interesting, but honestly, some of the best sounding amps I've ever heard were seductive liars. 

Best,

E

ghosthouse's avatar
ghosthouse
4,306 posts
 
George - I agree. 20 wpc being adequate to drive the Forests to moderate volume levels might not be particularly remarkable. I’ve read all the available on-line reviews about the Forests and am familiar with their reported specifications.  In light of statements from various A’gon participants however, I still found that adequacy unexpected given they are 87 if not 86 db sensitive speakers. Regardless, no one seeking speakers to pair with an SET or SEP amp is going to choose Totem Forests. BUT, more to my point, it is the quality of sound those 20 F7 watts produce with the Forests and with Silverline Prelude Pluses (more sensitive and also a nominally easy load) that I’m finding very remarkable. I’m not sure nature of the load provides the complete explanation for what the F7 does. In support of this statement, see the lengthy Six Moons F7 review where it was coupled with a range of very different speaker types. Link here:

http://www.6moons.com/audioreviews2/firstwatt2/3.html

Apologies to Blindjim for the (temporary, I hope) derailing of his original thread.

roberjerman
4,319 posts
 
Years ago Harry Pearson (TAS) tested a pair of 1000 watt Bryston monoblocs. He was impressed by the clarity of the sound - especially at low listening levels! He concluded having all that power available was certainly beneficial, regardless of listening level!
willemj
1,036 posts
 
A flat frequency response is crucial for a natural representation of the music. You don’t want the system to artificially boost or depress certain frequencies, and hence change the sound from what it was. As has been remarked, there are two sides to this.
First there is the speaker. It should have a relatively flat impedance curve without deep dips. There are plenty of speakers that present an easy load (Harbeth are good, but there are enough others), but there are also speakers with a devilish load.
Second there is the load dependency of the amplifier. A good amplifier should not be too troubled by impedance swings. Tube amps have a harder time here, given their design with output transformers. The Prima Luna that Eric referred to, with its absolutely massive frequency swings, is an extreme example of how not to design an amplifier. Compare this to an affrodable Yamaha AS 500, tested here: http://www.avhub.com.au/product-reviews/hi-fi/yamaha-a-s500-amplifier-review-test-395710 Even under realistic speaker loads it maintained a flat frequency response within 0.05 dB, an amazing performance not matched by many amps costing ten times more.
Taken together, I think speakers that are not easy to drive and amplifiers that are load dependent are just bad engineering, and are to be avoided. If you succumb, you will suffer the dreaded synergy problem and all the audiophile Angst that comes with it.

The second problem is power output. Most good speakers are not very efficient, so you will need lots of power to drive them. If you don’t have enough power, you will suffer clipping distortion on dynamic peaks, with a ’dirty’ distorted and compressed sound as a result. Again, some people like this, but it does not meet the criterion of neutral and life like representation. So how much do you need, not for average levels, but for dynamic peaks? A few years ago, having moved to a larger house and having upgraded from the Quad els 57 speakers to the less efficient Quad 2805 I decided to replace the 2x45 watt Quad 303 by a 2x140 watt Quad 606-2. There was no diference on small scale music, but it sounded much more realistic on the large and dynamic repertoire. I began to realize that I now also played my music rather louder, because the sound remained so clean. Since then, I have concluded that even more power may well further improve the sound. As another anecdote, Harbeth's Alan Shaw recently demonstrated his big M40.1 speakers in the Netherlands. Even he was surprised that on dynamic music the big amplifier that was used was putting out more than 500 watt per channel. Fortunately these days watts are no longer particularly expensive.
georgehifi's avatar
georgehifi
10,312 posts
 
prevailing wisdom about Forests needing a lot of horsepower to sound their best.

With this type of impedance and -phase angle, to they are EASY to drive,
https://www.stereophile.com/images/archivesart/TotFofig1.jpg
I would even say a 20w SE tube would do it. And they can’t drive ****!

And here’s what Stereophile measured test concluded:
"(fig.1) revealed it to be a very easy load for the partnering amplifier to drive. —will hardly stress even the most current-challenged tube amplifier."

Cheers George


ghosthouse's avatar
ghosthouse
4,306 posts
 
@georgehifi

I agree the Forests are an "easy" load (as has been noted in the reviews) and attempts to mate the F7 with a low efficiency/low impedance speaker would NOT be a happy pairing. I suppose there’s no surprise that 20-30 watts are enough to get some sound out of the Forests. The bigger surprise for me was the quality of that sound and that the F7 experience turned on its head prevailing wisdom about Forests needing a lot of horsepower to sound their best. Many comments here on A’gon to that effect (I still believe this to be generally true, by the way). Not only was the F7 able to drive them but it did so in a manner producing the best sound I’ve heard from them to date, even when compared to that with a 200 wpc Hegel or 400 wpc Taranis. Imaging, sound stage, detail and musicality add up to a magical experience: sheer, seductive listenability. In my O-pinion, the F7 is not just a "good" amp but a great one (paired with the right speakers, of course!) and an even greater value. Make the F7 exhibit one for Blindjim’s contention, "...there is more to how good an amp is than its ability to double output power with 50% drops in speaker impedance."

georgehifi's avatar
georgehifi
10,312 posts
 
absolutely astonishing when the F7 was used for a short time with 87 db sens. Totem Forests. It won’t peel paint but the sound produced is "to die for".

Here is a classic example of a good amp that doesn't need too much current to drive this easy Totem Forest load, but the same amp on a hard load that dips down much further in impedance and negative phase angle would be very handicapped. 

https://www.stereophile.com/images/archivesart/TotFofig1.jpg

Cheers George
ghosthouse's avatar
ghosthouse
4,306 posts
 
Picking up on Erik Squires’ reference to Nelson Pass....

I recently purchased a First Watt F7 amp. It generates 20 watts into 8 ohms and 30 watts into 4 ohms, so it doesn’t "double down". On a couple different levels it seems to embody "the less is more principle". I also think it shows not all watts are equally "capable". I’m mainly using it with moderately efficient Silverline Prelude Plus speakers (nominal 92 db sensitivity). Sound quality is extraordinary with the Preludes and was absolutely astonishing when the F7 was used for a short time with 87 db sens. Totem Forests. It won’t peel paint but the sound produced is "to die for".

At the risk of being accused of exaggeration, listening with it is like going from B&W TV to color, if you will pardon the non-audio(phile) analogy. And this by comparison to many different higher power amps including tube mono blocks and, more recently, Hegel H200 and Merrill Audio Taranis (both still part of "the fleet").

In the interest of full-disclosure, while the sound with the Forests was absolutely magical (the best they’ve ever sounded) concerns about yielding to temptation and pushing the volume into clipping territory and damaging a tweeter led me to discontinue that experiment. SPL readings of upper 70s db at 10 feet diagonal from the speaker (C weighting; Slow response) were easily achieved beforehand with no sign of strain - very satisfying levels for late night listening. With the more sensitive Preludes, low to mid 80 db peak SPL are regularly registered at the same 10 foot listening position. Completely satisfying levels for the kind of listening I do.

So, in reply to Blindjim’s question, "Would you buy an ‘uber expensive’ amp based more on its voice or soul, than on its ability to output loads of watts, even if you feel the amp may be somewhat under powered for the application?" The answer is "yes"...except for the uber expensive part.  The F7 lists for $3000.

(FWIW - I believe NP credits Dick Olsher with "the first watt is the most important watt" comment).

For more info:
http://www.firstwatt.com/pdf/prod_f7_man.pdf
czarivey
5,946 posts
 
Hmmm lemme guess:
In SS amps the "right" watts are perhaps ones delivered or possible to deliver from Right channel.

Case solved?
erik_squires
16,056 posts
 
It's not a matter of the first few watts. It is a matter of how the electrical frequency response changes based on the speaker.

A perfect amplifier has a flat electrical FR, regardless of the speaker. A weak amp may have it's FR adulterated by the speaker crossover, and that happens even before 1 watt.

Here is a measurements page from a Prima Luna design, to see what I mean:

https://www.stereophile.com/content/primaluna-prologue-premium-power-amplifier-measurements

You don't need an ideal amplifier to have good sound. Goodness knows most tube amplifiers barely meet this requirement, but it is a good indicator of the current drive, and guts of the amp.

Nelson Pass does make a related, but not the same, point about the first watt being most important. But he's talking about noise and distortion. He, rightfully, states that Signal to Noise at 1 watt is a far more important gauge of sound quality than Signal to Noise at full power (which we never spend time listening to).

Best,

E
georgehifi's avatar
georgehifi
10,312 posts
 
More than a few people over the years on these pages have said only those SS amps which double down in output power as impedance drops are truly special or worthy amps. Eg., 200 @ 8ohms; 400 @ 4 ohms; 800 @ 2 ohms; etc.

  To put it more simply:

No amp will exactly double all the way, anyone who advertises this is stretching the truth.
Ones that can come close to doubling (usually good bi-polar output amps) all the way to 2ohms, can push good current into hard to drive speaker EG: most Wilsons especially Alexia ( .9ohm epdr in the bass) and many other brands.

This is however not an indication of good sound quality, but your half the way there with a "very" important part of the equation to get it, but your half the way there with a very important part of the equation to get it. It's up to you then to sort these out with best one sound wise, as you taken care of the drive (current) factor.

Cheers George



Log in to respond
More to discover
80x80
Wisdom Audio P20m
80x80
Bricasti M5
80x80
Focal Chora