I agree, Bruno and I have had dinner together and talked and exchanged emails numerous times. A brilliant guy.
That is not to say that in the audiophile world there is not wiggle room for some differences of opinion, even between or among gifted and brilliant engineers, or even just smart and intuitive engineers who have good critical thinking skills.
One of the fascinating things about the audiophile world is that I'm guessing about half of what we hear is snake oil and the other half has at least some scientific basis, but it is often challenging to know which is which. Someone said that if you hear a difference and the cause can't be found in measurements, then you are not measuring the right thing.
I still remember the early days of solid state power amplifiers, when every one thought initially that they sounded really good, and later many realized that they did not sound as good as they thought, and then even later people realized that they needed to get more sophisticated in measurements, or interpretation of measurements to understand at least some of the causes of the audible shortcomings of of the early solid state amplifiers.
We may be in a similar early time with class D amplifiers. I do not believe, for example, that the conventional measurements we apply to class D amplifiers are adequate to measure some of the shortcomings that this new technology has. 20kHz THD, for example, is virtually useless for class D amplifiers. CCIF 19+20kHz with spectral analysis is much better, and quite useful, but I doubt that it catches everything. 19Hz+20Hz is a tempting test to catch some of the effects of bus pumping. I hope to touch on some of these tests in the second edition of my book.
This is not to say that there are not some very good-sounding class D amplifiers out there. Tremendous progress had been made in class D performance in the last 10 years, and Bruno is one of the people that has played a big role in that.
Cheers,
Bob
One of the spin-off's of Digital amps are their power supplies. it these can be made suitable for Hi-End performance requirements, they would save a lot in the shipping weight and costs.
The recommended digital amps with the JBL M2 speakers is the Crown iT5000 HD. Besides being ridiculously powerful, they actually sound quite good. Of course, the speakers have a lot to do with that great sound.
When the new analog CFA PA's arrive here, I will tap into the Crown amps cross-over to the amp go out to the CFA and listen. But the class D (?) is pretty good.... small, clean, powerful, light weight..... look forward to increased improvements.
THx-RNMarsh
The recommended digital amps with the JBL M2 speakers is the Crown iT5000 HD. Besides being ridiculously powerful, they actually sound quite good. Of course, the speakers have a lot to do with that great sound.
When the new analog CFA PA's arrive here, I will tap into the Crown amps cross-over to the amp go out to the CFA and listen. But the class D (?) is pretty good.... small, clean, powerful, light weight..... look forward to increased improvements.
THx-RNMarsh
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Are you talking DAC or ADC? Summing DAC's is pretty straightforward- unless you want to do some unusual thing. I have one DAC here that sume two outputs which are offset from 0 by a grey code to ensure that the outputs do not sit at zero. Interesting but not magic that I could see.
Summing ADC inputs is more complex but at 192 KHz the ADI 1940 can mix 8 stereo ADC's AD1940 Datasheet and Product Info | Analog Devices . making a PCB with 8 AK5394A's would be fun. Maybe Richard can bring his guys in on this. Theoretically summing 8 channels will get 9? dB improvement in SNR, already 123 dB, and if mixed correctly some distortion cancellation.
One of the new chapters in my second edition is a big one on switching power supplies in general, and for audio power amps in particular.
Of course, most pro amps of any significant power use SMPS already, be they class AB or class D amps. There are numerous different ways to implement SMPS supplies for audio power amps, including where to place the majority of the energy storage (reservoir) capacitance; on the input side of the main SMPS on the 385V intermediate bus, or on the dual-polarity main amplifier rails on the output side of the main SMPS. Similarly, there are different ways to deal with the issue of regulation.
Cheers,
Bob
I meant ADCs.
I wasn't aware of the ADI part. I'll have a closer look at that later today.
It looks like it should be fun for all sorts of things besides the topic at hand.
Mixed with some analog loops etc.
Why not just make the power supply and amplifier one? Instead of SMP and class D amplifier seperate.
We had similar experience, there is a lot more than just the DAC that figures into the final performance at these levels.
I pushed TI's digital amp guys hard on a composite approach. two independent switching systems seems far less insightful than an integrated approach. Got nowhere. Since the system has knowledge of what is coming (by a few samples) and what has happened the supplies could be more efficiently using the power if the amp and the supply communicate.
