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
Pass Labs is another that truly doubles down

Many manufacturers understate in their literature the 8ohm wattage so the 4ohm and 2ohm wattage looks to be doubling.
It's only on independent tests this shows up the 8ohm to be higher and the 4ohm or 2ohm not doubling.
 
Here's what I mean, both taken from Stereophile on one of the latest 60 .8 series.

Manufacture: Specified as putting out 60W into 8 ohms and 120W into 4 ohms (both 17.8dBW),

Stereophile measured:
The XA60.8 considerably exceeded that power, delivering, at 1% total harmonic distortion (THD), 150W into 8 ohms (21.8dBW, fig.4), 240W into 4 ohms

So you see 150w into 8ohms but only 240w (not 300w) into 4ohms, where's the other 60w gone????

Cheers George  

Because of this "voltage source" characteristic, the 300- series amplifiers double their power demands every time a loudspeaker impedance is cut by half. For example, the no. 336’s continuous rated output is 350 watts per channel at 8ohms; 700 watts at 4ohm; 1400 watts per channel at 2ohms.

Again, many manufacturers understate in their literature the 8ohm wattage so the 4ohm and 2ohm wattage looks to be doubling.
It’s only on independent tests this shows up the 8ohm to be higher and the 4ohm or 2ohm not doubling.

Levinsons specs: for 334. 300 series

8ohm=125w

4ohm=250w

2ohm=600w


Stereophiles tested specs

8ohm=139.9w

4ohm= 242.4w

2ohm= 430w

As you can see they don’t double, when tested.


Cheers George




Hi George,

The no.334 manual does not give a rated output for a 1ohm output load. 
8 ohm- 125; 4 ohm- 250; 2 ohm- 500 watts.
However John Atkinson found his test sample to measure quite closely to the ML literature:

"..John Atkinson also measured the No.334’s maximum output power using the Miller Audio Research Amplifier Profiler and a low-duty-cycle 1kHz toneburst to avoid loading down the AC line and the amplifier’s power supply. The result is graphically shown in fig.8. Though with this signal and one channel driven, the amplifier did meet its specification into 4 ohms, there was still a very slight shortfall into the demanding 2 ohm and 1 ohm loads. Into these impedances, 492W and 829W were available, these powers equivalent to output currents of 15.7A and 28.8A, respectively..."

N
So the upshot is, if you have speakers that are a kind load to the amp, then the amp is not called for to deliver current, and will stay reasonably flat in frequency response.

But if the speakers are a load that asks the amp to deliver current at certain frequencies, and the amp can't, then what happens at those frequencies is the amp "sags" in power at those frequencies and therefore cannot stay flat in frequency response, and becomes a tone control instead.

EG: Like the blackish grey trace shows in this graph of a tube amp that can't stay flat into a easy simulated speaker load. Which is plus and minus 6db!!! very far from sounding flat, and very mush a tone control.

https://www.stereophile.com/images/1116PLPPfig01.jpg

Cheers George