what are the pros and cons of either amp power specification?


What are the pros and cons of either amp: 1) an amp that is 100watts at 4 ohms and 50 watts into 8 ohms or 2) an amp that is rated at 75 watts into either 4 ohms and 8 ohms speakers?   For example,  the new POWERNODE 2021 is rated at 80 watts into 4 and 8 ohms where as the Sprout100 is rated at 100 watts into 4 ohms and 50 watts into 4 ohms.

thanks

RLJ


rlj

Showing 1 response by mulveling

If it’s Solid State output-transformerless, then being rated the same power at 8 ohms and 4 ohms is generally NOT a good thing. It typically indicates that the PSU and/or output stage and/or heat dissipation is not robust enough to handle the increased demands of a 4-ohm load - and that’s not good because it can certainly affect performance even on 8 ohm speakers (also realize that most speakers are not a fixed impedance across all frequencies - far from it, in fact). The "gold standard" is for an SS amp to "double down" its power when you half the impedance. Then you get to tack on extra buzzwords like "load invariant" and "high current", etc.

So the Sprout displays that nice doubling BUUUUUTTTTT...realize that some manufacturers may goose the numbers to make an amp look like it doubles down perfectly, when it doesn’t. For example, consider an amp that makes 250 Watts into 8 ohms and 400 Watts into 4, by some standard of clipping (typically 1% or 10% distortion level). The amp maker might decide the market will be more receptive to a 200 Watt / 400 Watt amp, so they could purposely spec their amp as such - technically they’re "under-rating" its power at 8 ohms to make it a clean 4-ohm power doubling on paper. Why does this matter? Because when you put this amp on a 4 ohm speaker with a dip to 2 ohms in the bass region, this amp may run out of gas (so to speak) compared to an amp that actually doubles 200/400/800Watts into 8/4/2ohms. Never buy amps from tricksey hobbitses lol.

Tube amps and autoformer-coupled SS amps (like McIntosh) are a different story. Then there's the matter that a particular speaker may have been voiced more for "load invariant" amps or for "constant power" amps. 

* And yes, sound quality considerations are a different matter, but generally amps with compromises in PSU / output stage / heat sinking are at least correlated with less than stellar sound quality.