Hypex Ncore

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@Julf, Ferrite beads on speaker lines are only a bad idea when you put one on each wire, because these things are hugely non-linear in the presence of current. If you put one on a neatly twisted pair it doesn't hurt because the audio currents in both wires cancel. [/QUOTE]

Thanks for the clarification, Bruno - I was thinking of the first case.
 
No. Phase is correct.
We'll try again. I just noticed you said gain is low. It sounds like only the hot input wire is connected.
Having done a lot of radiated emissions testing from Class-D amplifiers (to EN55022), I can safely say that common-mode RF noise on the loudspeaker output lines is always an issue, and sometimes a significant problem.
In general terms, CM on cabling is the way most emissions leave the amp. But by all means do the same measurement on the NC400, just to see where the various class D amplifiers stand relative to eachother.
 
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@Juhleren, the chokes are in the high voltage lines. The low voltage lines use ordinary SMD beads.

With regards to inductors in parallel, the only way that can make a load look more resistive is when you're driving only one frequency and the load is capacitive at that frequency. There is no generic "impedance improvement circuit" that you can slap across any speaker in the hope of making the whole thing less reactive. I think some SPICEing around may improve your intuitive feel for this problem.
)

Bruno
- thanks for the info -
I Was actually under the impression that class D amps generally didn´t like chokes in the HV supply, but obviously it is a matter of implementations :)

Regarding the autoformer, I think you read me wrong then. As I got it (and I may very well be completely wrong so rest with it) they work in principle by having the O/P of the amp driving one coil that then magnetically drives the speaker side coil which then drives the speaker. So the coil on the speaker is not just "across" it as much as it drives it hence a kind of serial connection.

You are right that a coil across the speaker terminals should just short DC to ground with the DCR of the coil and thus make a HP filter. The inductance of the coil "driving" the speaker doesn´t just work as a LP filter either (otherwise it´s L shouldn´t make it able to say anything but bass)

I am not trying to state a simple and workabel explanation here. I am just arguing for the "resistor hypothesis" to be missing something important.

And unless we know what it is missing, SPICE probably wont teach us much.

cheers,
 
Class D amps are not so much allergic to chokes in the power lines as to ringing. One should be careful how one uses chokes, because unjudiciously deployed they can indeed cause distortion. If the entire decoupling network (chokes & caps) is well damped, there is no problem.

An autoformer is no different from a normal transformer, except that you get to save some copper at the expense of isolation. The electrical equivalent network of an autoformer is a parallel inductance (primary inductance), a series inductance (leakage inductance which contrary to popular belief is not inherently lower in autoformers) and an ideal transformer.

So regarding the resistor hypothesis, what is missing is the leakage inductance and a trace amount of LF distortion. Plus, the rest of the amp. I didn't claim that the resistance is all there is to the "Mac sound". If asked to emulate that sound I'd have to do a fairly thorough characterisation measurements, perhaps even modelling some artefacts based on the schematics. But it's not something I plan to do for a living - I'd have a lot of work to catch up with the guys at Universal Audio for instance, whereas my gig is making stuff with "no sound". For me the ideal world is where people use targeted colouration on the music production end to control the sound, safe in the knowledge that the reproduction end doesn't try to do some "remastering" of its own by way of low-feedback amps, NOS dacs etc.
 
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For me the ideal world is where people use targeted colouration on the music production end to control the sound, safe in the knowledge that the reproduction end doesn't try to do some "remastering" of its own by way of low-feedback amps, NOS dacs etc.

I completely agree and the challenge when using "no coloration gear" in the reproduction these days, may be a temporary one that is based on varying mastering practices that 1) compensate for their own monitor gear, 2) produce for a market with "less than optimal" HiFi reproduction standards.

When problem 2) is implemented in problem 1), we who actually want to hear what is on the tracks suffer even more :warped:
 
For me the ideal world is where people use targeted colouration on the music production end to control the sound, safe in the knowledge that the reproduction end doesn't try to do some "remastering" of its own by way of low-feedback amps, NOS dacs etc.

Bruno, you'd better write "For me...." to make clear that this is your personal opinion, and therefore subjective. Which does not mean that I don't respect that opinion.
For me, and I hope the majority of audiophiles, the "ideal" world of music reproduction is largely met when I have the "illusion of being there", and to reach that goal IMO we don't necessarily need high feedback amps (class D or whatever) or OS dacs.
We seldom know how things exactly were at the music production end, and reproduction only gives an impression of that; the more it approaches the atmosphere of a live event, the more I like it, and once more, we are not limited by a particular class of gear.
 
My point is that adding euphonic distortion is best left to the production end. Every imperfect recording needs different euphonic treatment to maximise the sense of "thereness". A distorting amp or DAC is like a mastering engineer who leaves all the settings of his effects chain stuck in the same position regardless of the material he's given to master. Or like a cook who puts the same sauce on every dish. Such a cook would not even hold a job at McD's.

BTW I know you understand this point and are just trying to be quarrelsome. So I'm going to ignore your "input" from now on.
 
For me the ideal world is where people use targeted colouration on the music production end to control the sound, safe in the knowledge that the reproduction end doesn't try to do some "remastering" of its own by way of low-feedback amps, NOS dacs etc.

Bruno, you'd better write "For me...." to make clear that this is your personal opinion, and therefore subjective. Which does not mean that I don't respect that opinion.
For me, and I hope the majority of audiophiles, the "ideal" world of music reproduction is largely met when I have the "illusion of being there", and to reach that goal IMO we don't necessarily need high feedback amps (class D or whatever) or OS dacs.
We seldom know how things exactly were at the music production end, and reproduction only gives an impression of that; the more it approaches the atmosphere of a live event, the more I like it, and once more, we are not limited by a particular class of gear.

I thought Bruno made it completely clear in his original post
"For me" is written there and quoted

Out of interest Pieter, have you had an opportunity to listen to the ncores yet?
With SMPS and/or Linear supplies?
 
Out of interest Pieter, have you had an opportunity to listen to the ncores yet?
With SMPS and/or Linear supplies?

Yes, I listened to Ncores, and for comparison OEM Hypex modules driven by discrete input circuitry (solid state); they sounded equally good.
Power supplies were high quality linear (I don't believe in SMPS's sounding better by the way).
 
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