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
The Mac autoformer takes care that the amp drives the rated output across all loads 2,4,8, without raising distortion! (which these other brands dont do)

This reeks of MacItosh proper-gander
"Good designed" solid state amps are designed so the output transistors are used in their most linear part of their curve.

Cheers George
@atmasphere
Thank you.

You said earlier, there are a lot of amps that will work for you.

I agree. Finding the exact right one is the issue. Or exact right 3 for that matter. Or even finding the exact wrong ones helps too.

I think, knowing no better, it would be an easier task were more speakers 8 ohm impedance.

RE speaker eff
I often see sensitivity and impedance figures noted by makers on their speakers. Now, I’ve been reading where possible, measurements are made on which ever unit, and am often lost once more until the final analysis commentary arrives indicating if the tester felt positive or not about what all they saw from this or that model.

Although, I don’t routinely see an item declared as speaker efficiency, per se.

Is this a product of some other factors or measurements? Or is efficiency another term for sensitivity?

I’m thinking this is more involved than that somehow.

Best regards


Hi Jim,

Strictly speaking, speaker efficiency would be the ratio of acoustic power out to electrical power in.

However, it is common practice for the term "efficiency" to be used to refer to the sound pressure level (SPL) that would be produced at a distance of 1 meter in response to an input of 1 watt.

It is also common practice for the term "sensitivity" to be used to refer to the SPL that would be produced at a distance of 1 meter in response to an input of 2.83 volts.

2.83 volts into 8 ohms corresponds to 1 watt.  (2.83 squared/8 = 1). So for an 8 ohm speaker, that is truly 8 ohms, sensitivity and efficiency are equal.

2.83 volts into 4 ohms, though, corresponds to 2 watts (2.83 squared/4 = 2), which is 3 db more than 1 watt. So the efficiency of a 4 ohm speaker would be 3 db less than its sensitivity, assuming those terms are used in their most usual sense.

Also, keep in mind that as can be seen in measurements provided by John Atkinson in Stereophile, and measurements that are provided in reviews at SoundStage.com and elsewhere, manufacturer sensitivity and efficiency specs are often overstated by a few db. In some cases, I believe, because the manufacturer’s rating may be based on a single frequency, rather than an average across a wide range of frequencies.

Best regards,
-- Al

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When it comes to the perfect amp, Ralphs OTL Atamsphere’s are it.

But, and it’s a big BUT, you need the perfect speaker. One that is efficient, has a nice even resistive high impedance load across the frequency range, with virtually zero phase shift also across the frequency range. And Autoformers such as the Zero are a bandaid fix to get it, as they create other evils instead, similar to the Mac autoformers.

Full range speakers and horn speakers ("maybe Magie’s"??) are possible to have these 4 attributes, but are severely compromised in too many other areas, eg: colouration’s and distortions. Good luck finding any without these compromises.

Cheers George