Watts! How many do we need?

However, based on my basic search, amplifier specs don't advertise/disclose this info.I need one more variable.

@tee_dee The variable that tells the most about how an amplifier will sound is distortion vs frequency, which is a chart with a curve on it. Ideally, the curve is really a straight line across the audio band. If it rises with frequency, this can cause the amp to sound harsh and bright. The lower the frequency this happens, the more harsh and the more bright. The brightness is not a frequency response error, its caused by higher ordered harmonics being audible. The ear interprets such harmonics as 'bright' and also 'harsh'.

But you are right, many manufacturers do not publish this particular measurement! I'm of the opinion they really don't want the spec sheet actually telling you how the amp sounds.

is it watts that drive the speaker? (I know that if I put the + & - lead of my vm on the corresponding speaker posts. I get an AC volt reading which varies depending upon volume level.) But if it is watts that drive the speaker, and every watt is equal to every other watt, what is it that makes speakers sound different with different amps?

@immatthewj Watts drive the speaker. But most speakers are designed to be ’Voltage driven’. "Voltage driven’ is a short hand phrase that basically says the amp, while making power, should be able to act as a Voltage source, which in turn means that the amp can make the same Voltage regardless of load. You are familiar with what this looks like already: if the amp can double power as the speaker load impedance is halved, then its a Voltage source.

So the short hand can be confusing. However Voltage does not exist without current being present and vice versa. So in the end Watts are actually driving the speaker.

The reason amps sound different is how they make distortion on a particular speaker. Our ears convert distortion (harmonics) into tonality in the same way that harmonics of musical instruments define the tonality of those instruments. The ear is particularly sensitive to higher ordered harmonics (the 5th and above) since it uses them to tell how loud a sound actually is. But those harmonics can be masked from causing tonality if the 2nd and/or 3rd harmonic is high enough- this is why SETs seem to sound so musical despite having a lot more distortion (including higher orders) than any other kind of amp; the 2nd and 3rd harmonics are masking the higher orders.

Solid state amps often have much lower amounts of distortion overall, but the higher orders are not masked, causing the amp to sound brighter and harsher.

The most musical amplifiers are those that make very low amounts of distortion (SETs are typically 10% at clipping so they are right out) and that distortion will be the 2nd and /or 3rd harmonic, enough to mask any higher orders.

@invalid Yes, that’s true. But they advertise that pesky current thing on their website- take a look (and click on 'specifications').

Now lets do the math:

Giving the amp the benefit of the doubt, we set the speaker load impedance to one Ohm. Using the Power formula thus the Power the amp makes is the current squared. This amp does not make 160,000 Watts! They claim 6000 Watts into 2 Ohms, so the current flowing at that time is only 54.77 Amps... and if it doubles power into 1 Ohm (which it probably can do but not to full power) it would be double the current or only 109.54 Amps.

Obviously that current spec is something entirely different!! Most likely its 400Amps that flows when the power supply is shorted out for 10mS. So its really a measure of the capacitance in the power supply rather than the current that the output section can produce.

Thanks for your comment, but I am pretty sure I understand current and how it relates to solid state amplifiers performance characteristics. Sorry, but the article you refer to is so poorly written as to escape making any sense to me, hats off to you if you can understand the techno babble, with a bit of some kind of marketing. I am familiar with ohms law.

@ghdprentice I'm going with 'apparently not' in this case. The reason, which is pointed out in that article, is that current does not exist without Voltage and the two together make power according to this formula, which is quite simple:

1 Amp times 1 Volt = 1 Watt.

This means that if the amp can make the power, it has the current also. So it makes no difference if the amp is tube, solid state or class D.

When there is talk about current, absent of power, then its nonsense. For example, quite often solid state amps are advertised as having lots of current; not picking on anyone in the industry but I've seen '80 Amps' advertised many times.

Since Power is also (through algebra) equal to Resistance times Amperage squared, let's give the 80 Amps the benefit of the doubt and set Resistance to 1 Ohm. Thus the power is the Amperage squared. In the case of 80 Amps, that's 6400 Watts. To my knowledge there are no amps offered to high end audio that make that kind of power: Amps that make current beyond the power they also make do not exist.

If you think otherwise you are engaging in a myth. That is why I linked the article.

From my experience with solid state, current was the primary determinant if the amp was up to the task, the more the better. From my tube amp experience, it is far, far less important. So I went from high current 350 wpc solid state to 70 wpc tube amplification and my system sounds so much better it is amazing. It is a high quality amp… I am sure there is a difference between 70 wpc with an inexpensive light weight tube amp and a good one.

@ghdprentice 'Current' in the way you describe it above has little or no meaning. You might want to read this article which explains why.

@jfrmusic If you need over 100 Watts to make your speaker really sing, you have a problem- the speaker might be criminally inefficient unless you are in a very large room. The more power you need, quite often the harder it is for the amplifier to sound like real music. Most higher powered amps I've seen simply don't, although they are pretty good at sounding like electronics.