The buffer section consists of an opamp and a couple resistors. Nothing else is causing losses you clearly don't understand what you're saying. The efficiency matters because it lets us know how much of that 60mA the regulators are being loaded, is being drawn out of the lm4562's from the NC-500's.
I suggest you calculate that for yourself. Remember, power is voltage times current. Still think it would run very hot?
The lm4562's are used in several applications. But we are talking about the NC-500's now.
I don't need to. I already know it sounds like crap. Good enough for me. And I don't think Colin's losing sleep after hearing all the outstanding feedback on the Rev C board and SIL-994's.
What do you guys what anyways? Do you want Colin to just announce:
" hey guys I know there's been outstanding customer feedback on the rev C boards and SIL 994's, but I've decided to discontinue them and offer only the Hypex evaluation board version. The reason for this is because of what Julf, igorzep, SDK and all of the rest of the peanut gallery who never heard them is saying over on Diyaudio"
No it doesn't. 1.2k and 2k isn't the same load. And the input impedance doesn't tell you the exact power the amp will consume. Besides you are comparing a budget DIY amp to a flagship product. In Hypex's own flagship products they use discrete opamps exclusively.
Yes, it would help us to calculate the output current *if* we knew the actual efficiency of the buffer circuit. We don't. Instead we can look at the input impedance of the nc500 and apply ohm's law (as usually taught in 7th grade elementary school physics).
A 16 V voltage (assuming worst case) into a 1200 ohm load results in a 13 mA current.
Pity. It is a simple multiplication, not higher maths, and it would show how silly your comment was.
It had nothing to do with sound - it simply showed your hyperbole about "hot enough to melt the solder" was totally silly.
NC500 datasheet species input impedance to be 1k8, not 1k2:
http://www.hypexpro.com/wp-content/uploads/2015/03/NC500-OEM-datasheet-R4.pdf
Any competent opamp is able to drive this load, as confirmed in this same datasheet.
http://www.hypexpro.com/wp-content/uploads/2015/03/NC500-OEM-datasheet-R4.pdf
Any competent opamp is able to drive this load, as confirmed in this same datasheet.
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I have absolutely no opinion on the power efficiency of the buffer circuit (apart from the fact that 47 mA isn't unreasonable in any way). This discussion was about output current capability, not efficiency.
Thanks, so the current is even less. 16 V into 1k8 is 9 mA. To achieve a 26 mA current into 1.8 kOhm you would need a voltage of 47 V...
The discussion is about how much current is being drawn from the LM4562 we already know that the LM4562 datasheet clearly says that the maximum limit based on good quality standards is 23mA.
Assuming that the buffer is only 21% efficient is absurd.
Bavmike, it's about time to admit that most if not all "audio" opamps can drive an NC500.
Sound quality of the multiple options is a totally different affair, and discussing this is interesting but most of the time rather meaningless.
Sound quality of the multiple options is a totally different affair, and discussing this is interesting but most of the time rather meaningless.
Please start reading datasheets well: the 23 mA is with a 600 ohm load. The NC500 load is three times "easier".
I'm not buying that the LM4562 is only 15% efficient, and 85% of what's being drawn from the regs is being pissed away as heat.
because I don't understand what I'm talking about we are pi..sng away up to 8mA out of total expected load (18mA typical - 10mA required by NC500) if you wanna know why is Bruno stating 60mA (maximum) to be on safe side you should ask him or measure it yourself...
And the 150mA rating of the SIL 994 is at 75 ohms. Which opamp do you suppose is working harder to drive the NC500's?