What Class D amps will drive a 2 ohm load

dsper,
All amplifiers running 2 ohms continuously will get hot, independent of class. But I have seen that class D modules (Icepower, hypex, purifi) have current limit to protect the module from overcurrent.

As for thermal dissipation, musical signal has peaks, it never has the same power requirements as a full signal sine wave. So the manufacturers add dissipation to the modules in a coherent way for music listening.

If an amp was to be built to run full power sine wave at 2 ohms just for long term measurements, just add a lot of heat sinks and even a fan or two. It would do great on the benchmarks, but would make no sense for customers to pay and lift the extra weight.

As for distortion is simple: along with the Benchmark AHB2, the Purifi module is the lower distortion amplifier in the market, as far as we know (most manufacturers don't publish THD x power graphs, just single number specs).

The only caveat I'd have about the Purify 1ET400A as a separate power amp in the gain spec of 12.8dB.  I'm sure that doesn't hurt the distortion specs but may not be good for many people depending on their associated equipment.

Purifi 1ET400A has no buffer, so it is expected to a manufacturer to add a custom buffer, and add more gain as needed.

All we have here are a few manufacturers spruiking their new or yet to be released Class-D amps without any shame, saying they "can handle" the 2ohm load, making out they can drive this speaker to it’s best in the bass. Without presenting any measured proof of their claims, that they can almost double their clipping wattage from 8 to 4 to 2ohms.

With GaNFETs having 'on' resistances of only a few milliohms, its obvious that a class D amp using such devices will easily double power into 2 ohms (not that such is important for proper audio reproduction) as long as heatsinks and the associated power supplies can support the current. This has been stated before, its really not an issue of debate to one learned in the art.

  What I've learned lately on this thread is to avoid using speakers that present loads to the amp of less than 2 ohms. I believe if speaker designers and manufacturers decide to rule out the use of the majority of amps working well with their speakers, then we can certainly decide to rule out the purchase and use of their speakers.  

@noble100 +1 on this comment and post. This is exactly the issue- IMO/IME its irresponsible to create such low impedances where serious power is required for the simple reason that distortion will be higher, and increased distortion will make the presentation less musical.

why can't discussions of audio stuff, hifi stuff and music listening stuff, be non confrontational ?

really you have to ask this?? Because there's way too much BS and Voodoo in hi-end audio Mr D

Its not so much voodoo (although that is a problem); on this thread it really comes down to the posts of exactly one person.

Good quality sound? into hard speaker loads it’s all about current.

This statement is misleading. Its really all about distortion.

Spectron amplifiers can deliver peak currents of 65 amps, with a staggering peak power of 3500 watts per channel for over 500 msec (!), which allows the amplifier to deliver the full transient (burst of music) without current or voltage “clipping”. "

this statement is also misleading- here's why:


Current cannot exist without voltage. When the two are together you have Power, and the relationship is thus: 1 Watt = 1 Volt times 1 Amp.


If you don't know the voltage, you can use algebra to sort out the power anyway, using Ohm's Law. That relationship is used here:


Doing the math and giving the amp the benefit of the doubt, lets assume that the speaker load is 1 ohm. You'll see why in a second. Power equals Resistance times Current squared. So if we have 65 amps, the square of that is 4,225 watts into 1 ohm (just multiply that number by the impedance of the load if you want to know what 65 amps into higher impedances is). You can see right away that 65amps has nothing to do with the output of the amp. It likely represents how much current flows when the power supply of the amp is shorted for 10 milliseconds. IOW its really a measure of the capacitance in the power supply. FWIW, our MA-2 power amplifier (Vacuum tube class A triode OTL) has about the same current by this measure.


FWIW this sort of current number being bandied about is a common myth with solid state amps.

Purifi 1ET400A has no buffer, so it is expected to a manufacturer to add a custom buffer, and add more gain as needed.

It also has a disappointedly low 2.2k input impedance, so the use of most capacitor coupled (unless >10uf) preamps, tubes, or solid state or passive preamps direct in are out of the question if no extra gain is needed, which with today’s sources giving so much higher output, no extra gain is needed, so then neither would be an opamp buffer.

And if more gain is needed then a direct coupled opamp smd buffer is the only obvious option, again not capacitor coupled, solid state or tube buffer otherwise a massive 10uf coupling cap will be needed into that 2.2k input impedance.

WHY!! they keep making low input impedance amps these days is beyond me, go back to 48k (the once recognized industry standard) or even 100k like it used to be with tubes, makes for a whole better range of preamps ,tubes SS or passive able to drive them properly.

Cheers George