Do Amps matter.. in an Amp?

I have a buddy with the Maggie 3.7i. We tried three amps one day, level matched. The Magtech… stereo version, The Parasound A21 and the Orchard Audio GanF class d Stereo Ultra. The Magtech at 900 watts into 4 ohms, the Halo and Orchard at 400 watts into 4 ohms. 
 

All three amps handled the Maggie’s with no problem playing loud…. and they sounded more similar than different in most areas. Listed in order of warmth.. Halo, Magtech, Orchard… but the difference was slight and without hearing the others, any of the three would be good choices. 

sure, as you said, it's a weird measurement since it doesn't reflect any real useful scenario of use.

@dain Exactly.

Class D amps most definitely have power supplies!! It can have an enormous effect on how they perform.

I'm not saying this 'current' thing is bad! I am pointing out however that without context it can be really misleading. Take the example I gave where our 220Watt MA-2 amplifier (which is a tube amplifier) is rated at 80Amps! We put all that extra capacitance in the power supply because the amp does not use any feedback and so everything like capacitance in the power supply affects it.

We also developed a class D amp of our own design and it makes the same power into 4 Ohms as the MA-2 but has a much lower 'current' value. It however uses 37dB of feedback and so can reject power supply problems in a way that the MA-2 cannot. I think it sounds better on 4 Ohm loads too.

Don't get hung up on any single variable in the specs. The old maxim 'trust your ears' applies here.

@atmasphere sure, as you said, it's a weird measurement since it doesn't reflect any real useful scenario of use. Did I get that right? I still ask, as power supplies aren't cheap.. even if it's a 15 watt amp (BTW, great observation on why lower powered amps may be better designed since they prioritize better quality) it must have some spec a potential buyer may appreciate? Or is it all numbers for marketing sake and really you just need to trust your ears? Or even class D which I guess don't have a power supply except for what's coming in from the grid?

Or to say in another way, this measurement was into a shorted load

@dain I think you misunderstand- that current is not when the amp is driving a short, its when a short is placed across the power supply of the amp. The output section of a 1000 Watt amplifier would not be able to survive that kind of current!!

@hilde45 totally! It's the benefit of a good brick and mortar store, and in 'high end audio' so much is about fit with your room, other equipment, etc. they tend to let you try things in your system. I was happy to own Wyred, Rogue for a while, I tried Hegel, Acoustic Research, PS audio, Odyssey, er, perhaps one or two I forget.. but it's really vital to not get too distracted by specs and cost and focus on seeing if it works for your setup. Oddly, you get used to almost anything, so auditioning may not be the most scientific way to assess the quality of a product. Almost all of these were mono blocks, so that does make some things easier - haven't really tried many integrated amps. 

@kijanki and @atmasphere very knowledgable replies thank you! So if I follow, there's many 'dials' one can change to design an amplifier. Some have significance as measurements, some do not. I thought of this question when looking at power supplies that were all 5v but got more expensive as the amperage went up. Or as you say "These numbers might reflect good power supply, but have nothing to do with reality."

Or to say in another way, this measurement was into a shorted load - speaking of which I did trash one of these high average amps, and indeed, just like an arc welder it melted the circuit board! But as to if this means anything to making music fun to listen to.. I wonder, if you have a tube amp, even 3 watts should be pleasant enough to listen to, do these have other numbers like amperage and power supplies and damping and such to consider? I guess I just see certain numbers all the time but no real context as to why they are important, and why they do seem to have some percievable effect. At least on cost!

You've tried dozens of amplifiers? Literally dozens? How do you manage that? I'm jealous...and curious!

What does max amperage mean compared to the damping factor or the wattage change into different loads? Seems like an easy engineering question but I don’t see it discussed very often. 

If the speakers dip down into low impedance somewhere in the frequency range, then enough current is a good thing.

If it was 8 ohm from DC to daylight, then ho much current does one need?

I think that the Saunders amps are usually the “go to” with some of the Maggy range.

I’m stuck on amperage. Most product tout wattage, which I find misleading since the highest wattage amp I own has the least satisfying sound. My favorite amplifier claims >60 amps of current, and a few manufacturers state this measurement. But most don’t. Is it significant?

@dain Don't be stuck on this! 'Amperage', as @kuribo points out, has nothing to do with the power the amp can make. But I should point something out here!! Power (Wattage) is Voltage times Current. IOW, current cannot exist without voltage and so cannot exist without Wattage.

When you see enormous amperage ratings like you mentioned, usually its a rating of how much current will flow if the main power supply is shorted out for 10milliseconds. IOW really a measurement of how much energy is stored by the power supply capacitors rather than how much power (or current) the amp can actually into the speaker. 

Here's an example of what I'm talking about:

Maggies are 4 Ohms. If you had a 1000 Watt amplifier, the power formula states that the resulting current present when 1000 Watts is present is only 15.81 Amps!

Its not a bad thing that the amp might store this much energy. Our MA-2 amplifier, which can make 200WRMS into 4 Ohms, has a current rating of 80Amps. That's because it stores a lot of energy in its power supplies- but I would not want to be in the room if they were shorted out for something like this!

IMO/IME when manufacturers state numbers like this without any information explaining what is meant by them, its not a good sign and clearly causes confusion (which IMO is the goal). It certainly says nothing about how the amp will sound (which is caused by the distortion it make BTW). Put another way, you may be liking certain amps over others on account of their distortion. You can get lower IMD by increasing capacitance in the power supply. This is because at higher power levels, the power supply is more impervious so its voltage remains more constant and interacts less with the amplifier circuit.

However you can get around this a bit if you use enough feedback in the design! IME most amplifiers don't have nearly enough. So adding filter capacitance is one way to reduce intermodulations.

In theory, an amplifier with high current output capabilities is less affected by either the speaker or the music played before, but even this measurement can be greatly misleading. Is it peak current? Sustained?  Equal across all frequencies or only in the bass? 

Your amp would likely need that much current to drive difficult load, but 60A current thru 1ohm load produces 3600W  !!!   These numbers might reflect good power supply, but have nothing to do with reality.  As for damping factor - the easiest way to reduce output impedance is to increase negative feedback leading to, in extreme case, Transient Intermodulation Distortions (overshoot in time domain).  40dB of negative feedback will reduce output impedance 100 times.  Membrane motion damping is limited to DFmax=1.5  anyway, since speaker's resistance is in series.  We don't want to make it much worse, so output impedance should be at least 10x lower than speaker's impedance.   Output impedance might be important to produce constant voltage (voltage source) under changing output load, but again many tube amps have higher output impedance and sound fine. 

 
Assuming competitive market 100W amplifier should sound better than 200W amplifier if they cost the same and you don't need 200W.  Cost of larger heatsinks, bigger transformers, stronger transistors etc. can be used for better components and design.

I would suggest reaching out to Chris Brunhaver for power/speaker interaction answers. Or Ralph. He answers the phone.