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Class D Switching Power Amplifiers and Power D/A conversion

Ncore design refinement
Ncore design refinement
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Old 8th February 2019, 05:29 AM   #1
kazap is offline kazap
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Default Ncore design refinement

Ncore refinement might measure well:
“prototype Lyngdorf 8 x 400 Watt class D amplifier based a new patented class D amplification technology which is the brainwork of my co-founders of Purifi Audio, Bruno Putzeys and Lars Risbo. This is the first of any class of audio amplifier which is completely indifferent to frequency, level and impedance variations. The actual performance is difficult to measure due to limitations to even the best test equipment (AP555). But we are specifying max 0,00015% THD+Noise, at ANY frequency 20-20KHz at 100 W/4 ohms. Intermodulation distortion WAY below any other technology. Notice the output impedance - scaled in micro Ohm!” Peter Lyngdorf

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EDIT: see Bruno's post

Last edited by kazap; 21st February 2019 at 02:05 AM.
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Old 8th February 2019, 06:21 AM   #2
KaffiMann is offline KaffiMann  Norway
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Ncore design refinement
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Whatever's gonna happen, it will not be cheap...
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Old 8th February 2019, 06:48 AM   #3
googlyone is offline googlyone  Australia
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Ncore design refinement
Likely not, agree they will be looking for payback.

Oddly, I suspect that the cost of the device won't be inherently large, in that this will, in essence, be a bunch of high power DACs with tolerance for supply rails being saggy.

Ok... there will be some cleverness as if I tried this, I would be looking for very high speed switching at the output which would either make it fail or be gruesomely inefficient. Or expensive or all of the above.

I will be very interested to see how they negotiated this trade off!
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Old 8th February 2019, 07:12 AM   #4
FauxFrench is offline FauxFrench  France
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The fully numerical amplifier is coming and it is counter to the DIY idea of adaptation. When the ICs are ready, we as DIYs have little other option than to implement them and use them "as is". We may not even have to worry about making good power supplies which may be integrated in the design.
On the other hand, I see a lot of members using vacuum tube amplifiers. That is hardly because they offer the lowest THD values or best linearity (I'm no expert) but is based on the appreciation of sound. Sound is in the end subjective and may not be fully coherent with electrical data.

In the past, we designed discrete amplifiers with ample possibilities for individual adaptation and variation. We have many members who still master that art but they will become less in numbers because it is really complex work. Then came the chip-amps and our concern was to assure the best operating conditions for the chip while we were limited by the chip design itself. The monolithic class D (and T) amplifiers give us little room to deviate from the concept described in the datasheet. We can concentrate on the power supply, the output filter and eventually the input adaptation but we are bound by the chip layout.

The fully numerical amplifiers will be very expensive for some years before the successful chip-sets are available. Then, when the chip-sets are available and the Asian production robots are ready, the price will drop rapidly. But at that time, humanity may have more serious problems to attend to than sound quality.

Last edited by FauxFrench; 8th February 2019 at 07:19 AM.
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Old 8th February 2019, 09:14 AM   #5
Windforce85 is offline Windforce85  Poland
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From looking at the output impedance and the author's name, there is probably monstrual feedback loop gain inside of this amplifier, like noone has seen before. Interesting if its DSP engine is prepared for integration of driver's motional feedback in order to definitely close control loop around whole playback system. Looks like serious thing at the development, not a toy for audiophiles.
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Old 8th February 2019, 09:32 AM   #6
jan.didden is offline jan.didden  Europe
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@Windfore: agree, most probably multipole feedback loop(s)..

The caption under the 2nd graph says 'THD' but the graph Y-axis label says 'THD+N'. I guess it actually is THD+N, because it gets lower at increasing power which is typical for THD+N. So the real THD will be even lower.

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Old 8th February 2019, 03:03 PM   #7
Antoinel is offline Antoinel  United States
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I searched United States Patent and Trademark Office for Putzeys Bruno/Inventor Name and Risbo Lars/Inventor Name. The Assignee Name for Risbo's recent patents and patent applications is Texas Instruments. His/TI's last one is in late 2018. The last solo patent by Putzeys is US 8,289,097; in 2012!

I am not versed in Class D. Hopefully, you can extract the patent/application which describes Peter Lyngdorf's excerpt.
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Old 8th February 2019, 08:15 PM   #8
FauxFrench is offline FauxFrench  France
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Quote:
Originally Posted by Windforce85 View Post
From looking at the output impedance and the author's name, there is probably monstrual feedback loop gain inside of this amplifier, like noone has seen before. Interesting if its DSP engine is prepared for integration of driver's motional feedback in order to definitely close control loop around whole playback system. Looks like serious thing at the development, not a toy for audiophiles.
You mention an internal feedback loop. Due to my ignorance regarding "DD" amplifiers I will ask, isn't it so that a numerical amplifier operates on a description of the input that is so (absolutely) precise as the input sampling allows and needs no feedback?
Evidently, motion feedback will require a feedback loop. But without motion feedback and with high precision input sampling, for me to see it is a matter of converting the PCM description into a PWM description and the job is done? Few uses post-filter feedback anyway. Evidently, both a very precise and fast A/D for input sampling and a fast high-resolution DSP for conversion are needed.

Last edited by FauxFrench; 8th February 2019 at 08:18 PM.
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Old 8th February 2019, 08:27 PM   #9
Windforce85 is offline Windforce85  Poland
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I am not an expert in mixed signal systems control theory but I know that PWM power output stage will certainly need control loop in order to fully linearize and immune it from the load variables. Fast ADC feedback loop using digital signal processing is perfectly possible in acoustic frequencies and it is done already in more or less good way in some designs. For such sharp guys like them it will be piece of cake I assume...
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Old 8th February 2019, 08:28 PM   #10
MorbidFractal is offline MorbidFractal
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I would not wish to detract from the achievement but Mr Putzeys has already advertised a lack of confidence in his patents by not giving direct links to them. If I were to infringe on his claimed IP and he wished to complain I would invalidate the pertinent claims and ignore him.
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