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LUXMAN - SQ-N150 Tube Integrated


EmilC

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2 minutes ago, artto said:

What I said was virtually all Class D amps are not DIGITAL at all. The M32 is as close to true DIGITAL as it gets at the moment, other than requiring some kind of "analog" output to drive ANALOG speakes. Class D amps are NOT Direct Digital or Digital Feedback or Direct Digital Feedback amplifiers. However, the NAD/Zetex developed amplifiers are. Hence, the original, and I agree with it, designation Class Z

 

Nobody said a Class D amp was digital. I have repeatedly said they are switching amplifiers.

 

What you don't understand, and is the only issue of confusion is that the Class Z technology is still utilizing a switching output stage, which is Class D. It uses digital processing in the feedback and input to improve upon the switching amplifier performance.

 

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1 minute ago, Shakeydeal said:


I’ve put together quite a few outstanding systems over the years. How presumptuous of you to think I need a recording background to do so. Or anyone else. Your smugness is certainly apparent, but you should open yourself to other possibilities. I know you won’t. No matter to me, carry on.

NO. You are the one who needs to open yourself to other possibilities. You *might* learn something instead of being so presumptuous yourself.

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Just now, captainbeefheart said:

 

Nobody said a Class D amp was digital. I have repeatedly said they are switching amplifiers.

 

What you don't understand, and is the only issue of confusion is that the Class Z technology is still utilizing a switching output stage, which is Class D. It uses digital processing in the feedback and input to improve upon the switching amplifier performance.

 

Which is precisely why it is Class Z, as the the original inventors designated it.

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12 minutes ago, artto said:

Which is precisely why it is Class Z, as the the original inventors designated it.

 

Going in circles here.

 

You made a statement that people wrongly call a Class Z amp, a Class D amp.

 

My only point is that people that know how they work know that the output stage is still a switching output stage no matter what else you call it. The definition of Class D is exactly that, it has a switching output stage. Class Z is just a made up class because it is really just a Class D amp with different method of controlling the switching modulation of the output devices. Hence the "Class Z" chipset is added input modulation chip and the feedback chip, connected to a switching output amp stage.

 

Calling it a Class D amp is technically not wrong.

 

 

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18 minutes ago, captainbeefheart said:

 

Going in circles here.

 

You made a statement that people wrongly call a Class Z amp, a Class D amp.

 

My only point is that people that know how they work know that the output stage is still a switching output stage no matter what else you call it. The definition of Class D is exactly that, it has a switching output stage. Class Z is just a made up class because it is really just a Class D amp with different method of controlling the switching modulation of the output devices. Hence the "Class Z" chipset is added input modulation chip and the feedback chip, connected to a switching output amp stage.

 

 

ROFLMFAO.

 

You just can't admit it, can you.

 

Let's go through this again.

 

Class D amp = no "added input modulation chip"

 

Class D amp = no "feedback chip"

 

Class Z amp = "different method of controlling the switching modulation of the output devices"

 

Class Z amp = "added input modulation chip"

 

Class Z amp = DIGITAL "feedback chip" (yes, I'm correcting you)

 

But to you they are the same thing and both Class D. If that's the case, we should just throw out all amplifier Classifications all together.

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39 minutes ago, artto said:

ROFLMFAO.

 

You just can't admit it, can you.

 

Let's go through this again.

 

Class D amp = no "added input modulation chip"

 

Class D amp = no "feedback chip"

 

Class Z amp = "different method of controlling the switching modulation of the output devices"

 

Class Z amp = "added input modulation chip"

 

Class Z amp = DIGITAL "feedback chip" (yes, I'm correcting you)

 

But to you they are the same thing and both Class D. If that's the case, we should just throw out all amplifier Classifications all together.

 

Admit what? I admit you haven't a clue what you are talking about but why would I expect anyone that is not an electrical engineer and has no idea how any of this stuff works except for tidbits of information they misconstrue would even follow the simple concepts.

 

Do you even have a basic concept of electronics and circuit theory? Let alone any sort of background or education to where actually you have an advanced understanding of this stuff?

 

It's okay because if anyone that reads this that actually has a thorough understanding of the concepts discussed will see how confused you are.

 

Come back in maybe 10 years of studying and maybe we can have an educated conversation on the matter, until then I am not going to get through to a non-engineer type on any of this because of the lack of fundamental understanding and concepts.

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For anyone following it's extremely simple.

 

Class D amp = an amp with a switching type output stage

 

Class Z amp = has a switching type output stage

 

People with patents use Class Z because it's profitable. An engineer knows and understands that it's still a Class D amp because it has a switching output stage by definition. It just has a more advanced method of error correction. Don't fall into marketing and patent hoopla traps and confusions, people that understand the concepts don't and see things for what they truly are.

 

A Class AB amp is still a Class AB regardless of if it has global negative feedback or not. The performance difference between the two is due to the error correction but amplifier classification remains the same.

 

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1 hour ago, Marvel said:

I was falling asleep at work? Actually missed part of what artto posted, as I still have to get some work done during the day.

 

No worries, I respect your opinion and wasn't sure if I was just losing my mind or what misinterpreting what he was saying because I felt it was clear.

 

 

These chips from Zetex have been discussed in detail many times especially where I tend to hang out at diyaudio(dot)com. If anyone wants a good discussion of how the chips from zetex improves Class D amplifier performance here is a link:

 

https://www.diyaudio.com/community/threads/zetex-ddfa.117627/

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So people don't have to read through the whole thread:

 

 

I didn't say that the DDFA is an all-digital amplifier, there's no such thing when the final output is analogue. What I meant was that the input is digital and all the signal processing and PWM conversion is digital discrete-time, the final PWM output stage and the error feedback ADC (see below) are obviously analogue.

In a discrete-time system like the Zetex DDFA the ideal values of all the outputs are known at the clock frequency (108MHz); the modulator takes a discrete-time digital sampled-data input at the input rate (e.g. 44.1kHz, 48khz, 88.2kHz, 96khz...) and first sample rate converts this to the PWM frequency (about 850kHz). This high-resolution 850kHz signal is then converted to a 108MHz PWM signal (128 possible pulse widths per PWM cycle) and the resulting quantising error is fed back into the noise shaper.

Mathematically this is the same as an oversampled 7-bit sigma-delta DAC running at 850kHz, except that the 7 bit amplitude control for each pulse is done by a PWM signal not a PAM signal (multibit DAC); the area under each pulse and its time position are exactly known, assuming a perfect output stage. The noise shaping pushes the inband quantisation noise down to well below -120dB, just like any other high-resolution oversampled DAC.

Of course the signal is still a PWM signal at 850kHz not a sample-and held PAM signal, but the spectrum inband (up to 20kHz) is identical -- see the plots on the Zetex website. And after an analogue LPF the waveform looks analogue too, just like a single-bit sigma-delta DAC after filtering.

So unless you're saying that all DACs can't produce an analogue output after a reconstruction filter -- which would be a pity, since nearly all DACs on the market do exactly that -- then the DDFA PWM output after filtering is equivalent to a conventional DAC. If you don't believe this I suggest you take it up with Mr. Nyquist...

You don't need a 20+ bit ADC with hundreds of kHz sampling rate for the feedback digitiser, because this only digitises the integrated error between the actual power stage PWM output and the "ideal" PWM reference DAC.

The analogue error integration (in the analogue chips) means that any edge distortion effects are included, there's no lower-rate sampling as such in the ADC which can cause aliasing effects, the totla area under each pulse is what is being measured. This feedback is indeed analogue, but doesn't limit the performance because only the small residual error is converted.

The digital circuits then predistort the input to the PWM modulator which drives the actual power output stage to compensate for the timing and amplitude errors in it, such that it has the same performance as the reference DAC and the error signal tends to zero.

The end result is an amplifier with performance at the speaker output pretty much as good as the best DACs available have at the DAC output -- not my opinion here, this has been demonstrated by both measurements and listening tests. In fact, Zetex are also applying just the modulator chip as an 8-channel DAC, with performance up there with the best on the market.

I'm not guessing here about how this works, I designed the low-jitter (picoseconds) clock and PWM output stages that produce this reference PWM DAC output

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