At the end we have to compare apples with apples. The extraordinary THD figures of the purify are a matter of open loop gain in the 20kHz region and specially a matter of multipole feedback compensation network. I am quite certain that Bruno Putzey is capable to design an A/B amp that outperforms his class D-designs. All in all there is no evidence for a general rule claiming class-d may outperforms class A/B.
No but I don’t understand how someone could DIY a better implementation of the 3251 chip with integrated power supply than Icepower has done for $68 retail, in lots of 20. Even if you count your time for free, the parts alone will cost more.
Why would you make a class AB amp these days? Larger size? Less efficiency? Higher BOM? Nostalgia maybe, but not for any practical reason.
Or just build a home theater with active 3-ways crossovers on all the speakers. One can easily use up close to all 40 channels of amplifications. It appears that the 200AS2 has a 300W power supply, and the 100AS2 only has a 100W power supply. I would pay the minimal extra and get the 200AS2.
Practically, I can see some want to build class A amps for compression drivers.
That’s still 28dB worse. And what’s the power level of the amp at 1%THD+N/4R?
Let’s not forget that the Purifi is a 450w amp at 1% THD+N/4R
In a true academic overkill design better results would likely be possible. Like bridge-paralleling dozens of ADA4870-based ultra-high loop-gain composites ;-)
I agreed if you say that no high-power class A or class AB amps are measured better than Purifi. But, if I only want say 5W or less. I think one can do better than Purifi. Not sure if it will be cheaper than Purifi, however.
There a some pretty practical reasons to do so:
Some years ago I inheritated a collection of Hitachi LatFETs that looked at me saying: Hey, layzy chap, build something with us!
And I always liked the idea of a special laboratory amp with these features:
-Lowest noise and distortion possible
-Bandwidth several 100kHz
-bulletproof
-oscilloscope-friendly clean output signal without any pwm artefacts
And size, weight, efficiency, costs - do not matter here
Did you ever try to replace old school filament bulbs by LEDs in a mains bulb tester?
Yeah but what’s the point? Will is actually sound better?
We have reached the point where the electronics hardware of an audio system is no longer the bottleneck. The future advancements all lie in the realm of advanced spatial sound DSP algorithms, multichannel Atmos music, High res wireless transmission. And perhaps driver technology.
A little hint can be seen here:
https://www.futuresource-consulting...dio-megatrends-for-2022-tech-perspectives.pdf
I haven't seen any 5W or less amps that measure better. And if they did, somewhere else between the digital storage medium and the amplifier would likely become the weak link.
Absolutely. And that is why nitpicking THD values of 20kHz in the vicinity of noise level is irrelevant to audio experience.
I wholeheartedly agree.
And would add integrated amp+driver topologies, buzzword would be "optimized drive impedance profile" (vs frequency), in active speakers. The current standard voltage drive (and drivers optimized for it) is still a (small) brickwall left...
In the meantime I would be happy if my bluetooth handsfree would connect flawlessly with my mobile phone.
Sometimes there maybe some requirements beyond your point of view that are not covered by Icepower and similar industrial products.
Let me name a few that I put into my battery operated design:
-on-board low noise +-/12V supply
-on-board 6.3mm output jacks
-ribbon cable port for various audio front ends
-auto shutdown after several minutes without audio signal
-auto shutdown on low battery voltage
-total standby current in shutdown mode <100uA
-ribbon cable port for programming/diagnostics