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Class D Switching Power Amplifiers and Power D/A conversion

Quantifying class A quality.
Quantifying class A quality.
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Old 11th February 2019, 03:12 PM   #11
chermann is offline chermann  Austria
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Hi


my 2 cents


i had 28 years a Accuphase C200V and a P300V and its not Class A ...but
at the preamp I changed all caps and lucklythe amp played fine...very fine..nevertheless i sold it because my DAC (gustard A20H) sound better directly at the power amp



...the sound is always very nice but after doing DIY the relation between price and durability ....hmmm.. -----> you pay a lot for shiny, massive, commercial....blablabla.......
i accept a better craftsman ship and the durability


chris
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Old 11th February 2019, 03:23 PM   #12
Oneminde is offline Oneminde
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Buyers of audio equipment comes in different classes, have low or high interest, thin or thick wallet, have almost no to expert level knowledge, have no skill or a long list of skills he or she can pour into the project. People value different things. Some are hardcore old school (tubes) while other are always looking for the latest thing. Some are pure technical and couldn't care less about refinement and design. In the end, the one using cheap equipment might be as happy with his or here choices as the one spending $2.4 million dollars.

The Honeybadger class AB available through the diyaudio store can compete against the best class AB commercial units available and until a true superior class D amp appear, Hypex and Pascal is the way to go.

- Oneminde
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Old 11th February 2019, 03:28 PM   #13
chermann is offline chermann  Austria
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yop... i agree...some DIY project are very nice...
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Old 11th February 2019, 04:08 PM   #14
voltwide is offline voltwide  Ireland
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THD, IMD, S/N and damping factor are numbers you can certainly compare. Needless to say that beyond certain numbers achievements might be measurable but not audible. The actual reference of class-d seems to be Bruno Putzeys latest baby, the DD-amp. Based on the technical data I suppose it outperforms any class A on this planet.
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Old 11th February 2019, 04:12 PM   #15
Oneminde is offline Oneminde
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Quote:
Originally Posted by voltwide View Post
THD, IMD, S/N and damping factor are numbers you can certainly compare. Needless to say that beyond certain numbers achievements might be measurable but not audible. The actual reference of class-d seems to be Bruno Putzeys latest baby, the DD-amp. Based on the technical data I suppose it outperforms any class A on this planet.
I agree and IMD aren't specked typically which it should. Chn separation is utterly important as well. I have my ideas about superior class D but will certainly take a look at the amp you mentioned, there can be no harm in inspecting what others do. In the end, all I am after is "as good as possible"
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Old 11th February 2019, 04:57 PM   #16
Oneminde is offline Oneminde
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Quote:
Originally Posted by voltwide View Post
The actual reference of class-d seems to be Bruno Putzeys latest baby, the DD-amp. Based on the technical data I suppose it outperforms any class A on this planet.
I get a hint of a TON of feedback, digital correction etc. Not a fan of that. Sure, the THD+N is looks okay, besides massive spikes at 10kHz and 14-15kHz. On top of things, its more or less a digital amplifier. They might impress with good numbers, but remember, greater than 0.01% in THD (which is already an audiophile grade) has no real benefit since no one can detect it and is therefore only used for bragging, same with S/N in the range of -110-120 dB is absolutely acceptable - sure, the lower it is the better. But digital amplification these day ... mhe, I see no need for that. Pure analog class D with a minimum amount of closed loop or open loop feedback, heck yes. The rule is: Feedback is bad. Same thing with capacitor based DC servo on the output line.. If you know what you are doing, you can achieve outstanding performance without corrupting the signal via intermediate digital modulation.

Often it is not about you as an engineer and with that I mean your knowledge about electronics, but rather development of components and their ability to work closer to a theoretical ideal. The less ideal a component is the more the engineer must compensate and compensation is in reality not a merit of excellence. So, take two engineers: Both achieve the same performance, the difference is amount of components, topology, placement, EMI, IMD figures, efficiency etc - the one who reach stable function with least amount of parts and without compromises is perhaps the better engineer. On the other hand, a complex and heavy amplifier impress more.

Take the Vitus Audio SM-103 monoblock: 150w Class-AB w 1st 100w Class-A. S/N 110 dB and THD+N 0.01% - its not using toroidal core or R-Core or latest SMPS tech, nope, its using an EI laminated core transformer which is probably the worst thing you can use in an audio amplifier and all for the low price of $40 000/pcs ... Jebus.
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Old 11th February 2019, 05:02 PM   #17
Khron is offline Khron  Finland
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Well, they gotta squeeze out a profit SOMEwhere...

Those are made to be listened to, and optionally admired from the outside, not opened up and inspected, anyway

Oh, marketing...

Quote:
Originally Posted by Oneminde View Post
Take the Vitus Audio SM-103 monoblock: 150w Class-AB w 1st 100w Class-A. S/N 110 dB and THD+N 0.01% - its not using toroidal core or R-Core or latest SMPS tech, nope, its using an EI laminated core transformer which is probably the worst thing you can use in an audio amplifier and all for the low price of $40 000/pcs ... Jebus.
PS: If you're referring to the first graph on the DD amp thread, you'll note that's an IMD graph, not a THD+N
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Last edited by Khron; 11th February 2019 at 05:06 PM.
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Old 11th February 2019, 05:17 PM   #18
Oneminde is offline Oneminde
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Originally Posted by Khron View Post
Well, they gotta squeeze out a profit SOMEwhere...

Those are made to be listened to, and optionally admired from the outside, not opened up and inspected, anyway

Oh, marketing...
Sure, I get that. I don't mind when engineers poured their heart and soul into a project, splashed it with some art and refinement, spent months selecting components to up the performance and stability and had a blast doing so and its relative expensive to build. I totally accept that sometimes you have to pay for quality and a bit of luxury, but when you peak inside the Vitus amp, I am not impressed. What the heck am I paying for ... The Honeybadger with superb components and choices beat Vitus any day of the week even of it is specked and built like if Lexus decided to built a tank .... LOL - but at a fraction of the cost.


IMD, got it
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Old 11th February 2019, 05:50 PM   #19
doctormord is offline doctormord  Germany
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Quote:
Originally Posted by Oneminde View Post
I get a hint of a TON of feedback, digital correction etc. Not a fan of that. Sure, the THD+N is looks okay, besides massive spikes at 10kHz and 14-15kHz

If you're refering to this plot:


Click the image to open in full size.

This is IMD, so nothing is wrong about that. If not, what plot are you refering to?
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Old 11th February 2019, 06:46 PM   #20
ViennaTom is offline ViennaTom
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The turn on time turn off time and dead time distortion can be corrected by feedback. Problem is you need high loop gain. And high loop gain comes with high frequency. And at high frequency, the relative error introduced by these times becomes worse....

BTW I don' think that the easy explanation of THD and how much can be decteted says it all. There is also IMD (that sounds MUCH worse than pure THD!). Plus: IMD is related to THD and there are many ways to measure it so you can produce the number you want to see :-)
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