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Hypex NCore NC500 build

The discussion is about how much current is being drawn from the LM4562

Indeed. *Not* about efficiency or supply current. Thank you for acknowledging that.

we already know that the LM4562 data sheet clearly says that the maximum limit based on good quality standards is 23mA.
And to achieve 23 mA into 1.8 kOhm, you need a 41 V signal - and at that point the nc500 will be clipping rather badly.

Assuming that the buffer is only 21% efficient is absurd.
Assuming anything about efficiency, or even introducing it into the discussion is absurd (as you acknowledged above).
 
I'm just wondering from a layman's perspective

Thank you for honestly describing yourself as such.

if 60mA is being drawn from the regs, yet only 10mA of that is making it to the NC-500's, where did the other 50mA go?

Dissipated as heat, but who cares? 50 mA doesn't result in very much heat, so the opamp running perhaps 10 degrees warmer than the surrounding air wouldn't be a major issue.
 
Thank you for honestly describing yourself as such.



Dissipated as heat, but who cares? 50 mA doesn't result in very much heat, so the opamp running perhaps 10 degrees warmer than the surrounding air wouldn't be a major issue.



I'm not buying that 85% of the power is dissipated as heat. If the circuit is that horribly inefficient, then I would be redesigning it either way.
 
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I'm just wondering from a layman's perspective, if 60mA is being drawn from the regs, yet only 10mA of that is making it to the NC-500's, where did the other 50mA go?

If in this question you're referring to the NC-500 datasheet you posted up a while back, then the 60mA figure is the maximum. I agree its not clear if that figure of 60mA is perhaps taken momentarily on power-up, or if its there because the design permits OEMs to engineer their own board and they shouldn't assume they can have more than 60mA.

I'd hazard that 'where did the other 50mA go?' is making some kind of wrong interpretation of the data provided, but its not perfectly clear, even to this non-layman.
 
So where do you suppose Richard got the idea that the NC-500's draw between 50-70mA max from the buffer? After all he had them in his lab to test with his high end AP gear

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So where do you suppose Richard got the idea that the NC-500's draw between 50-70mA max from the buffer? After all he had them in his lab to test with his high end AP gear

No idea - he isn't part of this discussion, except through a proxy (you), so without any context and without any ability to ask him clarifying questions, all we can say is "who knows?".

Appeal to authority
is generally considered a rhetorical fallacy.
 
What has this to do with anything in this thread?



Well it seems that the fact the SIL-994's are so powerful and can drive a 150mA into a 75 ohm load, and 30 in pure class A is so wasteful. Perhaps it's wasteful buying an amp over 10w output just the same. Or is there any reasons sound wise we don't want to take amps right to the limit to get the best out of them ?
 
Bavmike, how about taking the rest of the day off from this forum, use your precious time to read this:
Biasing Op-Amps into Class A
and come back (preferably not before tomorrow) with hopefully a new, fresh look ......



Yes the 994's come out of the box running in class A up to 30mA. It's common knowledge that biasing into class A sounds better As Abraxito said, the lm4562 would probably only handle 1mA biased into class A.
 
Why you are into class D when you think class A sounds better?
Besides, when you would take the effort to read that article I linked, you would know that you can force an opamp into class A, also an LM4562 to drive a NC500.



You require some sort of buffer between a DAC chip and the class D NC-500 module. When this buffer is 100% discrete, and running in pure class A, it sounds far better. Likely the reason everyone says with the SIL-994 not a single detail is lost, but at the same time the sound is natural without a hint of listening fatigue. Listening fatigue is one of the biggest complaints from those who have heard other Ncore based amps and passed on them.
 
No not at all. The opamp in the buffer is no different. Running it in pure class A at levels far far below the maximum capabilities is no different than buying a 1000w amp and only using 10w of it. Because it sounds better!

It is more like making sure your amp can drive a 0.1 ohm load, just in case.

If you have a 1000 W amp, and only use 10 W on average, you still have headroom for transients, so there is actually a benefit from the overkill. But if you build in way too much headroom in a preamp or buffer, if doesn't buy you any benefits as the power amp will clip long before you get to use your headroom.