[kfz03110@yahoo.com]

Is there a equivalent of Wattage rating between a same brand Class A and class A/B amp? Say a Class A 60 W is equivalent to 250 W class A/B from the same manufacture ?

[FullRangeMan]

Is there a equivalent of Wattage rating between a same brand Class A and class A/B amp? Say a Class A 60 W is equivalent to 250 W class A/B from the same manufacture ?

No, both Watts are the same, Watts are V x A=W.

[FullRangeMan]

I will move this topíc to The Lab Circle due multi-posting in the Starting Block.

[Wind Chaser]

A watt is a watt. But anything is possible when it comes to imaginary alternative watts.

[JLM]

Welcome!

Because tubes tend to overload (clip) in a "friendlier" manner it's an adage that tube watts are "bigger" than solid state watts.  But in solid state a watt is a watt, however class A tends to run much warmer and thus less efficiently than class AB.

[Letitroll98]

I think what folks are getting at is apparent sound differences between various amplifier classes, which is a generality that falls down in the specific.  The generality is that Class A amps, and by default tube amps, sound more powerful than Class AB amps.  While there is a certain clarity to Class A that appears to offer more dynamics than the rated power would suggest, watts are watts and there's no substitute for big honking power supplies driving powerful output sections.  Other considerations are that it takes a lot of power output to increase the level of sound pressure through speakers, you need to triple or quadruple the power to hear much difference in sound level.  And speakers are always limited in max spl's, so more power doesn't always increase dynamics.  Perhaps the added clarity in some Class A amps is more important than incremental power increases in some Class AB amps.

[Speedskater]

With modern well designed accurate solid state amplifiers, there is no difference between Class A and Class AB amps.
All the above differences only apply to amps designed decades ago.
Note that some modern amps are designed to sound euphonic rather than accurate.

[JLM]

Power (watts) are in a logarithmic relationship to sound pressure levels (dBs), meaning that it takes twice the power to sound half again as loud (+ 3 dB), ten times the power to sound twice as loud (+10 dB).  So moving from 60 watts to 250 watts will add 6 dB.  Note that 1 dB is the smallest perceivable difference in sound pressure levels (spl) that the human ear can detect, so don't quibble over say 50 watts versus 60 watts (all else being equal) the difference in spl's can't be heard.  That's why I'm a fan of volume levels being displayed in dB of gain. 

Keep in mind that jazz and classical live music peaks around 105 dB and rock at 110 dB.  The "average" stereo listening setup loses about 3 dB compared to rated speaker efficiency due to distance being greater than the 1 meter standard.  OTOH manufacturers often over rate their speaker efficiencies.  So 1 watt = 0 dB of gain, 5 watts = 7 dB of gain, 10 watts = 10 dB of gain, 20 watts = 13 dB of gain, 50 watts = 17 dB of gain, 100 watts = 20 dB of gain and so on.

Speaker efficiency can make a bigger difference than amplifier power ratings, example:  a low efficiency speaker (say 83 dB/w/m) coupled to a 100 watt amp will produce 100 dB peaks at the listening position (83 dB/w/m speaker efficiency + 20 dB of gain - 3 dB distance penalty), which does reach peak live music levels; but a high efficiency speaker (say 96 dB/w/m) coupled to a 20 watt amp will produce 106 dB peaks; + 6 dB from 1/5th the power. 

[JLM]

With modern well designed accurate solid state amplifiers, there is no difference between Class A and Class AB amps.
All the above differences only apply to amps designed decades ago.
Note that some modern amps are designed to sound euphonic rather than accurate.

So true of most audiophile gear, especially speakers, as audiophile goals are most often to be entertained, not to hear what was heard in the studio.

[Wind Chaser]

I think what folks are getting at is apparent sound differences between various amplifier classes, which is a generality that falls down in the specific.  The generality is that Class A amps, and by default tube amps, sound more powerful than Class AB amps.

I've owned a few Class A amps and took a few home on loan; I never once had the impression that they sounded more powerful than Class AB amps.

[Letitroll98]

I've owned a few Class A amps and took a few home on loan; I never once had the impression that they sounded more powerful than Class AB amps.

I think that's what I said in the quoted text?

[RDavidson]

I will now go buy a Sony receiver because it has sufficient power and will sound the same, if not better, than any properly designed studio or audiophile amp.

I will write a letter of discontent to Harmon Group for confusing me with their production of JBL Pro speakers (designed to provide "the truth") and audiophile Revel speakers (designed to hide "the truth").

Good day!

[Tyson]

So true of most audiophile gear, especially speakers, as audiophile goals are most often to be entertained, not to hear what was heard in the studio.

You are correct, I do listen to my stereo to enjoy music.  I mean, if I were a recording engineer then a hyper analytic sound would be useful.  But otherwise, give me enjoyable sound over analytical sound every time.  I'm always surprised when people don't make that choice, but whatevs.

[Freo-1]

Is there a equivalent of Wattage rating between a same brand Class A and class A/B amp? Say a Class A 60 W is equivalent to 250 W class A/B from the same manufacture ?

It sounds like your asking about an amps headroom.  In other words, how much short term power can an amp provide for music transients.  For example, a lot of the Pass Labs Class A amp have a lot of headroom, so even though the amp is rated at 60 WPC, it can supply a short term amount of power of 120 to 160 watts to handle the musical transients. 


Also, tube amps tend to "soft clip" when reaching the max power out, which is easier on the ears than a SS amp that clips. 


By the way, there variants of Class A and Class A/B.  Benchmark has a Class AHB, which switches power supply rails depending on the load (Class H component).   Devialet has a AHD (Analog Hybrid Digital).  It allows the voltage to remain in Class A, while the current is supplied via Class D.  It sounds better than pretty much any other amp available at any reasonable price.

[Speedskater]

a soft clipping tube amplifier can give the illusion of more loudness.

[smargo]

I've owned a few Class A amps and took a few home on loan; I never once had the impression that they sounded more powerful than Class AB amps.

agreed - ive had class ab amps that sound better than class a amps and vice versa