OK, got a chance to check the documentation. Voltage gain about 2.3, voltage swing 15 V max (output), output impedance 100 ohm max.
It sound like you are picking because I gave you a measured and reasonable answer that doesn't seem to satisfy you? I find that puzzling and hence I asked.
Please read post #10508 again, it does provide an answer. It's a "convention" and a general rule we have followed for decades, that won't change, it is history.
convention ənˈvɛnʃ(ə)n/ noun
1. a way in which something is usually done.
That is all. It is a convention that we have known for decades and one that is rooted in the thoughts of Thiele and Small and those who added to our knowledge going back to the 70's and 80's. I could spend an hour plus digging them up, but seems superfluous.
Many flout with that convention, I texted Michael Lenehan of Lenehan Loudspeakers (http://lenehanaudio.com.au/)
"If you are awake, what would you say is the minimum impedance for a 4 Ohm speaker?"
Answer I got back:
"Usually after the box tuning impedance peak at say 150/200HZ you may see around 2.5 to 3 Ohm."
That is the experience we designers have, but the convention, the way things are usually done, is to avoid dropping below about 2.8 Ohm if possible. I think that is admirable, and if you can prevent it from dropping below 3.2 Ohm, then that is even more admirable.
Many raw drivers also drop below 3 Ohm when doing raw impedance plots for measuring Fs and T-S measurements, especially when using vented boxes. So even premium raw driver manufacturers seems aware of this.
Please note I said 'convention' and if the IEC says something different, it does not mean we can't keep following what we believe is a reasonable and acceptable rule that has been around for a lot longer.
I have texted Brad Serhan of Axis VoiceBox and Orpheus Loudspeaker fame and await his answer too and will report here.
Between the three of us we have near 80 years of hard-earned experience behind us, building and designing, measuring etc. That must count for something. We design in the 'real world' and we have our methods.
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Another easier method of bridging 2 NC400 amp -> custom made a pair of XLR + a jumper with 47nf/200V cap.
Think this DIY is simpler and more flexible.
Think this DIY is simpler and more flexible.
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Joe,
We clearly have a communication issue here.
I keep "picking" because I was confounded by the very precise number you gave, 2.83 ohm, so I asked how that number (two times the square root of two) was arrived at. I kept asking, because you never answered my question about the specificity and derivation of that number. Had you said "A safety margin of 70 % or so seems an established standard", I would have understood that you are talking about a rough, empirical value established through experience (and I would have agreed with you). But something like "2.83", with 3 digits of precision, and clearly derived from a mathematic formula, is something else.
So where in that message does it explain how that very precise number was derived, or even where you got it from?
Do you understand the difference between rough, empirical "rule of thumb" values, and precise values derived from definitions and mathematical formulas?
We clearly have a communication issue here.
I keep "picking" because I was confounded by the very precise number you gave, 2.83 ohm, so I asked how that number (two times the square root of two) was arrived at. I kept asking, because you never answered my question about the specificity and derivation of that number. Had you said "A safety margin of 70 % or so seems an established standard", I would have understood that you are talking about a rough, empirical value established through experience (and I would have agreed with you). But something like "2.83", with 3 digits of precision, and clearly derived from a mathematic formula, is something else.
I did. Here it is in its entirety:
I am clearly a lot older.
No connection to the nominal relationship with 2.83V and 1 Watt for 8 Ohm. That is of course related to voltage sensitivity (not efficiency).
But if somebody wants to say 80% is better than 70.7%, I won't argue on that score.
Probably in this instance IEC came up with 80% and was preceded by Neville Thiele and Richard Small by some time I suspect. Standards change, so got no beef with that.
Just for curiosity, I will ask some of my fellow designers what they follow and if they say 80%, then so be it and I will report it here. Fair enough?
So where in that message does it explain how that very precise number was derived, or even where you got it from?
Indeed. And had you said "70 %", I would have agreed. Instead you said "2.83 ohm". A very specific, precise value (as I keep pointing out, again and again - can you please address that specific issue?).
So yes, we agree on "something like 70 %, but 80 % is even better". 70 % of 4 ohm is 2.8 ohm, not 2.83 ohm (or exactly two times the square root of two).
Please understand I am not disagreeing with your ballpark figure (it is a pretty arbitrary value in any case), what I disagree with is providing a very precise number, with 3 digits of precision, and one that, funnily enough, just happens to be exactly the same as another commonly used value in loudspeaker measurements (the voltage needed top produce 1 W into 8 ohm, a value that is precisely 2.83 V and indeed derived from a definition of the units, involving twice the square root of two).Between the three of us we have near 80 years of hard-earned experience behind us, building and designing, measuring etc. That must count for something. We design in the 'real world' and we have our methods.
Do you understand the difference between rough, empirical "rule of thumb" values, and precise values derived from definitions and mathematical formulas?
I could swear that Julf is Bruno in disguise
Thanks, but I think that statement would make Bruno swear...
I don't and no reason for you to have such. I have decided not even to read the rest of your post past the above sentence, this is just getting too silly.
I have answered your questions very well, indeed there was a paper presented to AES circa 1980 that discussed a quasi-2nd order crossover that mentions 5.65 Ohm and indeed the crossover drops to exactly 5.65 Ohm at the crossover frequency as shown in the maths and it was designed that way to conform what we knew was the convention then. If you don't understand that, then you are just being a contrarian - argumentation for the sake of it. Not interested.
End of story.
Thanks for proving my point.
Funny how you try to answer something you haven't even read.
Any pointers to that AES paper? Do you know (and can you explain) why the crossover drops to that precise value? What is the maths behind it?
Don't want to drag this totally non-hypex-related stuff on more than necessary. I am just somewhat concerned when somebody throws around all sort of strange statements without being able to back them up in any way.
Opinions are opinions, and are of course totally OK when presented as such. Practical experience is great - when presented as such. When things are presented as precise facts, it is appropriate to be able to justify them, and explain the rationale behind them. Not being able to do that brings the integrity, knowledge and trustworthiness of the person into question.
Good. Let's move on to something more relevant to Hypex Ncore, shall we?
Wouldn't the needless mixing of 2 different PS outputs be less-than-ideal? Seems like the 2x5 should be used exclusively, just like all the other Hypex SMPS offerings.
I don't think the SMPS is defective and am unsure about the voltage. I'll give it a shot once I'm ready to button up the enclosure.
Hopefully Josjev or someone else with a NC400/SMPS1200A400 combo can chime in. Would be great if they could measure and/or try the alternative wiring (exclusive to J4) and provide feedback on any differences.
It certainly seems like mine were producing way more than the expected +5W. I measured the outside of my Ghent stereo enclosure at close to 120 degrees F last Summer. I can now very comfortably rest my hand on the SMPS heatsink after several hours at moderate volume, albeit with the enclosure top removed and improved case ventilation.
@josjev - are you able to give it a try?
Not really. It shouldn't matter.
Not implying it is defective - it would just verify if the voltage is at the setting where the internal regulator kicks in.
That is why I would like to verify if it now runs using the internal regulator or not.
Things are still in flux. Might add a few more holes to the enclosure.
Edited to add - No intention of any further wiring changes.
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An externally hosted image should be here but it was not working when we last tested it.
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OK, that should be just enough to trigger the "external aux voltage provided" detector.
An externally hosted image should be here but it was not working when we last tested it.
Kind of tough to read. Larger resolution version of the corrected wiring diagram.
http://i1308.photobucket.com/albums... - Revised Diagram 2_zpsmpxgxcic.jpg~original
=-=-
...and here's one midway teardown/rebuild.
An externally hosted image should be here but it was not working when we last tested it.
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That measurement was shortly after powering it on, with no load. It appeared that it was still climbing slowly.
- Disclaimer -
It's entirely possible this change has no benefit.
The tweeters on my floor-standers were replaced recently (don't ask) and I might of made a mistake on the initial wiring of the amp. There's some ambiguity in the original diagram that Hypex support provided.
I'm hopeful someone else with the same NCore/SMPS combination can give it a try. If you search around you'll find quite a few threads mentioning the excessive heat from the SMPS1200A400 + NCore combination.
To me that really sounds like the extra heat from the internal regulator on the nc400.
When the case was torn apart for the rebuild, I noticed some searing on the inside of the top enclosure nearest the large SMPS capacitors . Didn't notice any discoloration above the NC400's.
Ahhh... Perhaps the issue comes from the intermingling of the regulated and unregulated supplies (jumpers J7+8 set to regulated). I sure hope that's the case as it's far easier to move a pair jumpers than to rewire the whole thing.
Ahhh... Perhaps the issue comes from the intermingling of the regulated and unregulated supplies (jumpers J7+8 set to regulated). I sure hope that's the case as it's far easier to move a pair jumpers than to rewire the whole thing.
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It appears that the diagram provided by Hypex works just fine, assuming you don't attach anything else to J4.
In the event you do connect anything else to J4 you must also move the J7 and J8 to unregulated. A bone-head move on my part, but at least some lessons were learned
Thanks for all your help Julf!
-Sten
In the event you do connect anything else to J4 you must also move the J7 and J8 to unregulated. A bone-head move on my part, but at least some lessons were learned
Thanks for all your help Julf!
-Sten
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