NAD C 390DD - WHF Review??

jaxwired

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This digital amp from NAD is really a new breed of amp. Sure is pretty...
NADC390DD_600.jpg
 

Blackdawn

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Looks nice, any idea of prices? Whats the advantage of digital amplification? The information still has to be converted to analogue and sound waves for us to hear in the end.
 

jaxwired

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Good question. Here's the difference. A much much simpler and shorter signal path. That means a more accurate signal. Compare the two. First diagram is a normal system. The second diagram is the NAD digital amp.
x745M2-t_AAS.jpeg
x745M2-t_DDAS.jpeg
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Blackdawn

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Thanks Jaxwired for the diagram. I hope the NAD will be good and well priced. Didn't Onkyo bring out a digital amp below £400 a year or two back?, I think it achieved moderate reviews.
 

manicm

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Blackdawn said:
Thanks Jaxwired for the diagram. I hope the NAD will be good and well priced. Didn't Onkyo bring out a digital amp below £400 a year or two back?, I think it achieved moderate reviews.

The Onkyo was simply a normal analogue amp with a built-in DAC. If this NAD is a trickle-down from their 5k M2, then it's much, much more than that - it is a broadly speaking digital amp - NAD's special class of 'D' amplifier.

And hence don't expect it to cost less than 500 quid I would think, perhaps even a bit more.
 

Andrew Everard

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manicm said:
And hence don't expect it to cost less than 500 quid I would think, perhaps even a bit more.

US price is expected to be around $2600, and it's set to go on sale soon – it's expected in US shops in the first quarter of next year.
 
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Anonymous

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jaxwired said:
This digital amp from NAD is really a new breed of amp. Sure is pretty...

NADC390DD_600.jpg

Old hat, no? Direct digital amps have been around for a while, usually referred to as 'class D'

http://en.wikipedia.org/wiki/Class-D_amplifier

See halfway down the 'signal modulation' section for direct digital drive.

Given that a number of posters on here get all twitchy about using a wall wart switch mode power supply, imagine the horror of using a switch mode power supply (which is effectively what a D class amp is) as your output stage.
 

manicm

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andy8421 said:
jaxwired said:
This digital amp from NAD is really a new breed of amp. Sure is pretty...

NADC390DD_600.jpg

Old hat, no? Direct digital amps have been around for a while, usually referred to as 'class D'

http://en.wikipedia.org/wiki/Class-D_amplifier

See halfway down the 'signal modulation' section for direct digital drive.

Given that a number of posters on here get all twitchy about using a wall wart switch mode power supply, imagine the horror of using a switch mode power supply (which is effectively what a D class amp is) as your output stage.

Not quite, dear chap, unlike Class A amps, so-called Class D amps are quite fuzzy in the definitions of their topology. If you read up on NAD's M2 you'll find it radically different to others. And they don't call it a Class D amp anyway.
 
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Anonymous

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manicm said:
andy8421 said:
jaxwired said:
This digital amp from NAD is really a new breed of amp. Sure is pretty...

NADC390DD_600.jpg

Old hat, no? Direct digital amps have been around for a while, usually referred to as 'class D'

http://en.wikipedia.org/wiki/Class-D_amplifier

See halfway down the 'signal modulation' section for direct digital drive.

Given that a number of posters on here get all twitchy about using a wall wart switch mode power supply, imagine the horror of using a switch mode power supply (which is effectively what a D class amp is) as your output stage.

Not quite, dear chap, unlike Class A amps, so-called Class D amps are quite fuzzy in the definitions of their topology. If you read up on NAD's M2 you'll find it radically different to others. And they don't call it a Class D amp anyway.

I must be a little slow off the mark this evening. Apologies for that. To my mind, the reports of NAD's M2 match the description of a classic direct digital class D amp. Whether NAD call it that is of course another matter. Would you be kind enough to point out where I am going wrong?

From NAD's website:

From CD's 44kHz/16-bit signals through to off-server 192kHz/24-bit high-resolution audio the signal remains in the digital domain with all controls happening in DSP. Even the final analogue output to speakers is a gain by-product of the PWM switch-mode output stage rather than a conventional DAC.

From Wikipedia's description of a class D amplifier.

DSP-based amplifiers which generate a PWM signal directly from a digital audio signal (e.g. SPDIF) either use a counter to time the pulse length e.g.[4] or implement a digital equivalent of a triangle-based modulator.

The structure of a class D power stage is essentially identical to that of a synchronously rectified buck converter, a type of non-isolated switched-mode power supply.
 

manicm

Well-known member
andy8421 said:
manicm said:
andy8421 said:
jaxwired said:
This digital amp from NAD is really a new breed of amp. Sure is pretty...

NADC390DD_600.jpg

Old hat, no? Direct digital amps have been around for a while, usually referred to as 'class D'

http://en.wikipedia.org/wiki/Class-D_amplifier

See halfway down the 'signal modulation' section for direct digital drive.

Given that a number of posters on here get all twitchy about using a wall wart switch mode power supply, imagine the horror of using a switch mode power supply (which is effectively what a D class amp is) as your output stage.

Not quite, dear chap, unlike Class A amps, so-called Class D amps are quite fuzzy in the definitions of their topology. If you read up on NAD's M2 you'll find it radically different to others. And they don't call it a Class D amp anyway.

I must be a little slow off the mark this evening. Apologies for that. To my mind, the reports of NAD's M2 match the description of a classic direct digital class D amp. Whether NAD call it that is of course another matter. Would you be kind enough to point out where I am going wrong?

From NAD's website:

From CD's 44kHz/16-bit signals through to off-server 192kHz/24-bit high-resolution audio the signal remains in the digital domain with all controls happening in DSP. Even the final analogue output to speakers is a gain by-product of the PWM switch-mode output stage rather than a conventional DAC.

From Wikipedia's description of a class D amplifier.

DSP-based amplifiers which generate a PWM signal directly from a digital audio signal (e.g. SPDIF) either use a counter to time the pulse length e.g.[4] or implement a digital equivalent of a triangle-based modulator.

The structure of a class D power stage is essentially identical to that of a synchronously rectified buck converter, a type of non-isolated switched-mode power supply.

So called switching Class D amps cannot be described as such (taken from Absolute Sound):

'Functionally, the M2 is an “integrated amplifier” that replaces a DAC, preamplifier, and power amplifier. The M2 eliminates from a traditional signal path all the electronics of a DAC as well as the active analog gain stages of a preamplifier and power amplifier. It does this by converting the PCM signal from a digital source directly into a pulse-width modulation (PWM) signal that turns the M2’s output transistors on and off. That’s it—no digital filter, no DACs, no multiple stages of analog amplification, no interconnects, no jacks, no analog volume control, no preamp. The conversion from the digital domain to the analog domain occurs as a byproduct of the switching output stage and its analog filter. This is as direct a signal path as one could envision. '
 
A

Anonymous

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manicm said:
So called switching Class D amps cannot be described as such (taken from Absolute Sound):

'Functionally, the M2 is an “integrated amplifier” that replaces a DAC, preamplifier, and power amplifier. The M2 eliminates from a traditional signal path all the electronics of a DAC as well as the active analog gain stages of a preamplifier and power amplifier. It does this by converting the PCM signal from a digital source directly into a pulse-width modulation (PWM) signal that turns the M2’s output transistors on and off. That’s it—no digital filter, no DACs, no multiple stages of analog amplification, no interconnects, no jacks, no analog volume control, no preamp. The conversion from the digital domain to the analog domain occurs as a byproduct of the switching output stage and its analog filter. This is as direct a signal path as one could envision. '

"So called switching Class D amps cannot be described as such (taken from Absolute Sound):"

Err, says who?

To be clear, NAD have not designed a new amp architechture, the concept of a direct digital drive to a switch mode output stage is well known, and if Wikipedia is to be believed, falls under the heading of 'Class D'.

Rather like class A, B AB and so on, D is used to define the output stage of an amp. In the case of class D, that is a switch mode output, driven by some form of pulse width modulation.

The pulse width modulator can use an analogue waveform as its input, or in the case of direct digital drive, a digital signal. This gets processed by a codec before driving the output switch mode output stage directly.

This is exactly how the NAD operates, and is therefore in my book a class D amplifier. If it looks like a duck, and quacks like a duck....

From Wikipedia on class D amplifiers:

Signal modulation

The most basic way of creating the PWM signal is to use a high speed comparator ("C" in the block-diagram above) that compares a high frequency triangular wave with the audio input. This generates a series of pulses of which the duty cycle is directly proportional with the instantaneous value of the audio signal. The comparator then drives a MOS gate driver which in turn drives a pair of high-power switches (usually MOSFETs). This produces an amplified replica of the comparator's PWM signal. The output filter removes the high-frequency switching components of the PWM signal and recovers the audio information that the speaker can use.

DSP-based amplifiers which generate a PWM signal directly from a digital audio signal (e.g. SPDIF) either use a counter to time the pulse length e.g.[4] or implement a digital equivalent of a triangle-based modulator. In either case, the time resolution afforded by practical clock frequencies is only a few hundredths of a switching period, which is not enough to ensure low noise. In effect, the pulse length gets quantized, resulting in quantization distortion. In both cases, negative feedback is applied inside the digital domain, forming a noise shaper which has lower noise in the audible frequency range.
 

krazy_olie

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Well traditionally a class d amp requires an analogue signal, I think the point of this is that it uses the actual pcm signal to drive the switches so the amp is effectively the DAC. Sounds neat
 
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Anonymous

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manicm said:
andy8421 said:
This gets processed by a codec before driving the output switch mode output stage directly.

This is not true of the NAD.

Really? Scroll up to post #2 and have a look a the block diagram of the M2. The block marked 'Codec' looks like a codec to me.
 

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