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
kosst_amojan
2,095 posts
 
@blindjim 
I wish it were as simple as you would like it explained to be. Voltage gain is just a fixed value of the circuit design. How that plays out in dB actually heard depends on how well the amplifier drives the speakers. dB can be used a lot of ways to describe many things. Atmasphere can explain that jazz better than I can. Suffice it to say, an amp with 20 dB of gain can produce vastly different results bases on the speakers it's driving. That might be just barely adequate with some 85 dB efficient speakers and wild overkill for some 103 dB efficient horns. 
mattmiller's avatar
mattmiller
1,180 posts
 
This is why I buy McIntosh Double or Quad balanced design. 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 gives the Mac a very non fatiguing sound especially when listening loudly for long periods. So much so is this true that the Grateful Dead used Mac amps in all live performances because they loved this type of sound and shared it with all their fans. Did I mention they never break either...and last forever!  Woodstock spread beautiful music throughout Max Yeagers farm using McIntosh amps! These amps were abused and yet they rocked the hell out of that place.

Go ahead and spend gobs of money on those pure class A amps that burnout after 7-10 years...not me.

Matt M
kosst_amojan
2,095 posts
 
@mattmiller 
The Grateful Dead did NOT use Mc amps for ALL their live shows. They used them for about 2 years to power the Wall of Sound PA until they retired it. Beyond that they used mostly a variety of Meyer Sound PA rigs all the way to their retirement. 


almarg's avatar
almarg
8,673 posts
 
Kosst_Amojan 12-14-2017
It's called impedance matching. The closer a load matches the impedance of the source, the more efficient the energy transfer. Generally you want the load to be at least twice the impedance of the source to avoid odd coupling effects. The ratio of impedance difference also defines the damping factor which can significantly effect speaker behavior.

Kosst & Miketuason,

The following statement appears in the manual for the McIntosh MC601 that is listed in Mike's system description.  I believe similar statements appear in the documentation of other McIntosh solid state amplifiers which use autoformers.  And this is what I was alluding to in my previous post, although I referred to performance benefits rather than benefits to long-term reliability.  (Kudos to Mattmiller for citing both benefits):

All solid state power amplifier output circuits work best into what is called an optimum load. This optimum load may vary considerably from what a loudspeaker requires. In the case of more than one loudspeaker connected in parallel, the load to the power amplifier may drop to two ohms or even less. A power amplifier connected to a load that is lower than optimum, causes more output current to flow, which results in extra heat being generated in the power output stage. This increase in temperature will result in a reduced life expectancy for the amplifier.

The special Balanced Winding Autoformer creates an ideal match between the power amplifier output stage and the loudspeaker.

Also, regarding the comment about damping factor, the MC601 has a specified damping factor of "greater than 40," which presumably means effective output impedances of the 8, 4, and 2 ohm taps of approximately 0.2 ohms, 0.1 ohms, and 0.05 ohms respectively, all of which of course are very small fractions of the impedance of most speakers.  Which in turn reinforces the notion that the multiple taps are provided mainly to benefit the amplifier's output stage, as opposed to optimizing interactions with the speaker, such as impedance interactions, bass damping, and energy transfer.

Regards,
-- Al
 

atmasphere's avatar
atmasphere
7,068 posts
 
I’m reading thru amp measurements done here and there, and often the terms get conveyed as ‘db’ losses or gains of voltage, I suspect. When the DB comes up, I am lost.
@blindjim Decibels are a logarithmic expression. They are handy because our ears are logarithmic as well. Voltages and audio equipment in general are linear expressions, so sometimes conversion is needed.

1 decibel is the least difference the ear can detect.
3 db is a minimum easiest change in volume that we hear. +3db requires twice as much power, -3db is half the power
6 db is a doubling of voltage, not power. This can be a bit confusing!
10 db is what we perceive as 'twice as loud' and requires 10X more power
20 db is 100x more power.  30db is 1000x more power.

In amplifiers there is something known as 'golden decibels', an expression that comes from the radio broadcast industry. 3 db represents a doubling of power, and to hear any significant increase in volume you need 3 db, so this gets increasingly expensive and in amps, the more power the less likely it will sound like music. This is why speaker efficiency is so important.

Voltage gain can be expressed as a ratio and can also be expressed in decibels. Here is a handy calculator if you need to make the conversion:
http://www.sengpielaudio.com/calculator-gainloss.htm
More to discover