What Class D amps will drive a 2 ohm load

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

Custom buffer adds gain and increases impedance to 47k ohms. As seen on current NC500 based amps such as Nord or Apollon. Just Google it before complaining... These modules are NOT finished products yet, manufacturer is supposed to add their buffers.
For all in one, buffer+power section+power supply, see Hypex nCore MP series or ICEpower. The bufferless modules are for manufacturers wanting to differentiate their implementations.

Custom buffer adds gain and increases impedance to 47k ohms.

There’s no need for it in many cases, as sources and preamp have enough gain these days. It’s just "another opamp in the signal path" that’s not needed in many cases if the input was high enough instead of 2.2k, who wants that in hi-end if it can be taken out and one less opamp yay!!! gotta be good for the sound, and the business.
I think that’s a very legit observation or "complaint" as you would put it..

Holy crap - 49 amps. Didn't know this one existed

https://www.hypex.nl/product/nc2k-oem/79

Here's Apollon's version:  https://www.apollonaudio.com/hypex-nc2k-monoblock-amplifier-apollon-audio-nc2kslm/

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.

The reason you see this has to do with the fact that a filter often has to be installed between the audio input and the encoder (comparitor or the like). The filter is there to remove high frequency noise that might otherwise get amplified and add to the noise floor of the amp. But good high speed comparitora have issues of their own and can be unstable with a high impedance inputs. Hence low input impedances if there is no input buffering.

There’s no need for it in many cases, as sources and preamp have enough gain these days. It’s just "another opamp in the signal path" that’s not needed in many cases if the input was high enough instead of 2.2k, who wants that in hi-end if it can be taken out and one less opamp yay!!! gotta be good for the sound, and the business.

This statement is incorrect. Of course there is a need for an input buffer in many cases- a lot depends on the encoding scheme of course (for example with PWM the gain is based on the difference between the amplitude of the triangle wave in the circuit and the input signal). Things might not work out in the design that you have enough gain- particularly if feedback is employed. So an opamp or instrumentation amplifier might be used to make up the needed gain. Quite often this isn't a lot of gain, maybe a gain of 2 to 10. You could do it with an input transformer which has certain advantages, but it should be obvious that an input transformer adds a whole set of problems of its own.


Our preamps can drive such low input impedances- any preamp that supports the balanced standard can, but in high end audio such preamps are quite rare.