High end Class D amps?

Combined, these two give’s you what’s called EPDR, (Equivalent Peak Dissipation Resistance) and that can give the amp a very nasty load impedance to look at.
Good big current bi-polar amps don’t mind seeing this
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Class-D tends to quickly drop off it’s current starting under 4ohms down to 2ohms, look at any Class-D "independently measured" spec and you will see that, they never come close to doubling wattage from 4 to 2 to 1ohm, many even go backwards, showing severe current limitations into low EPDR impedances, this is limiting bass performance and becoming like a tone control, rolling off the bass instead of staying flat to 20hz.

This statement is blatantly false. Class D amps are limited in their ability to play low impedance (and severe phase angles) in the same manner as traditional solid state, although in practice a class D amp usually has a much lower output impedance than most traditional solid state amps.


Be-it class D or traditional solid state, if the output power is dropping into lower impedances, this is entirely due to the power supply and not the topology of the amp. At anything less than full power, any class D amp made in the last 5 years will act as a nearly perfect voltage source with any conventional speaker, with loads as low as 0.5 ohms no worries (since their output impedance is likely less than 100th of that). 

This statement is blatantly false. Class D amps are limited in their ability to play low impedance (and severe phase angles) in the same manner as traditional solid state,

No it’s not, and you know it and are in denial, your just once again in "product protection mode for your yet to be released Class-D".
 Just try to get any Class-D to perform as well as an amp with bi-polar output like a big Gryphon's into a pair of Wilson Alexia’s, the Class-D will be shamed.

Well this is an excellent example of how George has no idea what he's talking about. Sheesh.

George, perhaps you could come up with some evidence of your preposterous claim?? You know what they say- photos or it didn't happen.

No you have no idea, or, as I said you are in "product protection mode" and need to say the opposite for your future release. Most probably the latter I would think.

I’ll state once again as yet NO!! Class-D (and that also goes for my choice Class-D Technics SE-R1) will perform as good into a pair of Wilson Alexia and such, with their EPDR bass loadings like a hi current Gryphon Antillion etc etc can.

George - You've brought up this notion of EPDR in several class D threads, but haven't explained how it relates to class D. This is a term that was made up by a Stereophile reviewer to try to explain why linear amplifiers had a hard time driving speakers with a reactive load. Specifically, speakers whose current demands are not linearly related to the voltage across the speaker terminals. 

In a linear amplifier, this will cause a higher than expected thermal load on the output transistors because the high current demand can exist even with a high percentage of the rail voltage across the output devices. 

In a class D amplifier, the output transistors don't care about the voltage across the speaker since the voltage output only affects the duty cycle, not the power dissipation. They are constantly switching on and off at their oscillation frequency regardless of the voltage across the speaker. As long as the amp can handle the current demands, the fact that the load is at all reactive is irrelevant. 

If you disagree with these statements, please explain why. (And don't just repeat your previous statements since so far you haven't described how EPDR relates to class D). 

Obviously, you can contrive a situation where a given class D amp does not have the current capability to drive a particular load at the desired voltage, but this true with a class A or A/B amp as well. And, in fact, the thermal challenges are much more difficult with a class A amp, and even a class A/B amp, to meet a specific desired current capability.