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Old 11th January 2012, 09:12 PM   #1511
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Quote:
Originally Posted by Bruno Putzeys View Post
I think I'll be in trouble (wife waiting in bed) if I stay up late enough to give your reply the consideration it deserves tonight. So tomorrow
I get it it's her who drew this then...
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Old 11th January 2012, 10:04 PM   #1512
iand is offline iand  United Kingdom
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Quote:
Originally Posted by Bruno Putzeys View Post
@iand, I know how the Zetex works in much better detail than I showed in that post, but I don't think the detailed operation detracts from the basic idea that it's comparing the power stage output with the output of what is essentially a small-signal 1-bit DAC and feeding back the integrated error into the digital domain through an ADC.

Of course that needs to add further loop gain to shape the quantisation noise of the correction (which is determined by the system clock as well). But still the amplifier essentially ends up reproducing the spectrum found at the 1-bit DAC "reference". All of it. Just try adding an extra, externally generated analogue signal. It gets amplified. The circuit cannot differentiate between the intended signal and any you add externally. So the "reference" is truly a DAC. That's why it has to be this good.

This arrangement does have its merits, mind you. Since the reference contains roughly the same HF as the output, the error signal is essentially ripple free. This eliminates "ripple aliasing distortion" (i.e. the gain change the ripple would otherwise cause in the modulation process). But you get the same in an ordinary PEDEC controller.
I don't think we're disagreeing about how the Zetex DDFA works or its advantages -- it was just that you said you couldn't understand why the complexity was needed, so I was pointing out that it wasn't just a power amp.

As you say the DAC has to be pretty damn good, but at least there are few other error sources apart from this, you could say the power amp function is pretty much distortion-free on top of this, since the reference DAC output and the PA output are essentially identical -- looking at the results, the performance of the entire DDFA circuit is almost the same as the reference DAC alone. And you can use it as a multichannel solution for active speakers including crossovers and EQ.

Processing the error feedback signal and the feedforward signals digitally also opens up many possibilities for effective current/power limiting and amplifier and speaker protection (including dynamic EQ and driver excursion limiting) as well as "ideal" (distortion-free) gain limiting/clip prevention (using digital lookahead) and so on -- it's possible to do many things like this with digital algorithms that are impossible with analogue circuits.

Of course this is really moving into the realms of multichannel DSP where many amplifier designers fear to tread -- and where many audiophiles would say we shouldn't go because it ruins the sound, ignoring that many of the same techniques are used in the studio before they ever get their precious recordings...

Ian

P.S. I'm not trying to plug the Zetex solution, but speaking as an engineer it seems an elegant solution to building a large part of the sound reproduction chain at relatively low cost and with great consistency and flexibility. Digital in and speaker(s) out has its advantages :-)

P.P.S. But it's even more overkill for a single-channel power amp only...
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Old 11th January 2012, 10:33 PM   #1513
bbggg is offline bbggg  United States
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Quote:
Originally Posted by mr_push_pull View Post
starts with M
Bruno sidestepped the issue. Sounds like a confirmation.
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Old 11th January 2012, 10:43 PM   #1514
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I'd be happy to find that Meridian thinks the NCORE is a confirmation from Hypex.
based on interviews I've read, Bob Stuart seems one of the most down to earth guys in the business. I'm curious if it goes into an active system.

...

some Googling later:
News | whathifi.com

The speaker uses a single 8.5cm aluminium-cone wideband drive unit powered by a 100W wide-range super-linear low-feedback amplifier, this covering frequencies down to 200Hz.

At that point the downward-firing, relfex-port-tuned 14cm aluminium cone bass driver, powered by a 150W Class D amp rolls in.
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Old 11th January 2012, 11:54 PM   #1515
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Hi Bruno,
I am quite surprised about your definition of digital and analogue.
Since you pointed to this paper, I hope you are willing to discuss it, even if it is not a specific ncore topic.
Until I read your AES convention paper 353 I always said a digital
signal would be any signal where we use a digital protocol (using only certain discrete values) for coding the information.
But you are stating: 'What makes signal digital is whether the recipient interprets it as such.'

I am really wondering why a digital information protocol should flip to analogue just by being fed into an analogue recipient.

Examples:
If we use a traditional triangle modulator for our PWM, then the information is coded in a duty cycle that allows any value from 0 - 1. No quantization, every value is possible, like we are used to it from analogue world.
Yup, intuitively I would call this an analogue signal.

Instead of an analogue triangle PWM modulator we could use a uC to generate a PWM. Different from an analogue triangle modulator such a PWM is not able to deliver all duty cycles, but will show quantization steps, depending on the chosen resolution.
Lets have our digital protocol like this:
2 bit resolution and we can have the following duty cycles: 0 1/3 2/3 1
PWM frequency may be any typical value used for class D PWM, i.e. 400kHz.
If we use this protocol for coding music and feed it by a half bridge to an analogue speaker ==> IMHO it would still remain a signal with digital information coding. Why should I suddenly call it analogue? Just because I feed it to an analogue transducer?

Erhm, well of course a 2 bit resolution might not be most fortunate - but I am definitely expecting that DSPs which can do such a PWM in real time with 16bit...24bit resolution and even can handle a fast post filter feedback loop will become cheap within some years. Why should I call such a system analogue?
Of course such a system will still have to handle all the intruding analogue headache like unstable supply, limited switching speed and dead time adjustments as well as non linearities of the output filter, output impedance, back EMF ...
But the information coding would be digital. Should we really call it analogue just because we have chosen a digital protocol that is suitable for an analogue transducer?

Coming from the reasoning above your definition really feels counter intuitive for me. Why did you define it as you did? I am sure you had a reason, but this reason is not obvious to me.


Bye
Markus
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Old 12th January 2012, 12:13 AM   #1516
matjans is offline matjans  Netherlands
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On a somewhat different matter than pure tech, here's my sketchupped "artists" impression of a case. As you can see, I'm not that much of an artist.

Turns out that a mate of mine has a CNC router (diy) that "should" be able to do aluminium and he was actually happy to test it out somewhere in the (not so near) future.

Still a lot to be done, but I'm aiming for a kind of Linn Klimax look. Really cool. Sort of a sidewalk-tile (stoeptegel??) meets fondleslab meets klimax-esque thing(y).

Try searching google images for the linn klimax. I especially like the "roofed" connector section at the back. Sort of a cross reference to Linn (who I think started it) and Devialet (yeah right!). Don;t forget to add KLIMAX to the query in google if you have your filters set to none (NSFW results). W in this case may also be wife (not that I have one, but hey gf is almost wife sometimes).
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Last edited by matjans; 12th January 2012 at 12:22 AM. Reason: added some nonsense. I'm good at that.
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Old 12th January 2012, 12:33 AM   #1517
tinitus is offline tinitus  Europe
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Originally Posted by Bruno Putzeys View Post

Let's call it "pleasantness" then. Indeed, to call euphonic distortion "musicality" may be giving it too much credit.
I have different 'indicator'

its the drama in classical music
you will know when you hear it
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Old 12th January 2012, 12:34 AM   #1518
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so you're basically talking about a DSP controlling the switchers and an A/D converter providing the digital feedback information? I would indeed call that a digital amp. but no matter how I look at it I can't see any way to avoid the A/D part, since one must take analog feedback information back into the digital domain in order to keep the amp digital.

wouldn't that need a very precise ADC with the added complications (jitter like distortion etc)?

looking naively at it... a performance ADC is anything but simple and in order for the idea to be effective it would need to be fast too. could we compensate for A/D conversion errors in the digital part of it? hm...
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Old 12th January 2012, 02:24 AM   #1519
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Wow, you engineering knuckleheads sure know how to put a damper on an exciting thread

Here I was all excited to read about impressions of the NCore from early adopters, followed by enthusiastic responses about a potential case design. Now you guys go off into some goofy, boring diatribe about digital theory as if anyone on a DIY audio forum would be interested in that nonsense. he he he

In all seriousness, as much as you guys want to debate quantum physics, could you start another thread and leave this one to those of us who use a computer for email and the internet and a calculator to balance our checkbook.

Every time I get an email notice that someone has responded to this thread I get all excited thinking I am going to read someone's experience with their new NCore build or there is NCore enclosure news. Sure enough when I get here, you pocket-protector guys have hijacked this thread again

I'll be patient until you guys get this out of your system and then we can get back to the important stuff - how does the NCore sound and how are the NCore amp builds coming along.
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Old 12th January 2012, 03:31 AM   #1520
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Originally Posted by slowlearner View Post
Wow, you engineering knuckleheads sure know how to put a damper on an exciting thread

Here I was all excited to read about impressions of the NCore from early adopters, followed by enthusiastic responses about a potential case design. Now you guys go off into some goofy, boring diatribe about digital theory as if anyone on a DIY audio forum would be interested in that nonsense. he he he

In all seriousness, as much as you guys want to debate quantum physics, could you start another thread and leave this one to those of us who use a computer for email and the internet and a calculator to balance our checkbook.

Every time I get an email notice that someone has responded to this thread I get all excited thinking I am going to read someone's experience with their new NCore build or there is NCore enclosure news. Sure enough when I get here, you pocket-protector guys have hijacked this thread again

I'll be patient until you guys get this out of your system and then we can get back to the important stuff - how does the NCore sound and how are the NCore amp builds coming along.
Hear! Hear! - from one of the "latent" readers of this thread.
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