NAD C298 Class D power amplifier impressions

NAD C298 Class D power amplifier impressions

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Harry Flashman

Original Poster:

19,863 posts

248 months

Wednesday 5th April 2023
quotequote all
You lot are basically enablers, and I have the willpower of, well, something with not much willpower.

frown

I suspect another amp will be incoming soon, damn it.

Edited by Harry Flashman on Wednesday 5th April 16:44

OutInTheShed

8,867 posts

32 months

Wednesday 5th April 2023
quotequote all
How big is this room where the OP wants so many watts?

AdamV12V

5,124 posts

183 months

Wednesday 5th April 2023
quotequote all
OutInTheShed said:
How big is this room where the OP wants so many watts?
Room size isn't what determines how many watts he needs, it's the power needs of the speakers he owns.

Sure he may have got away with a smaller set of bookshelf speakers if the room isn't large (it looks like a decent sized living room loosely based on the pics anyway), but he has bought the ones he has! I guess one other option instead of mono-blocking with a 2nd amp, would be to downsize the speakers to a set easier to drive, but it seems like both he and the mrs are very happy with them.

I don't think you can really have speakers that are too big for a room, sure they may be bigger than needed, but never too big (other than aesthetics really). You can however have speakers that are too small to fill a room.

outnumbered

4,323 posts

240 months

Wednesday 5th April 2023
quotequote all
AdamV12V said:
They are also knocking on for £10k a pair new, and there's an old rule of spending a similar amount on your speakers as your amps to get the most out of them... I know that's a very rough rule, but easy to get out of sync if you buy speakers 2nd hand for a snip, then buy your amp new for similar money.
I never really subscribed to that rule myself, but these days with Hypex/Purifi Class D amps, you can get enormous power and world class technical performance for not much money at all. The NAD 298 is based on Purifi modules, so I think the OP is already doing OK there, it’s rated at 340W at 4 ohms, and those figures will be correct.

OutInTheShed

8,867 posts

32 months

Wednesday 5th April 2023
quotequote all
AdamV12V said:
OutInTheShed said:
How big is this room where the OP wants so many watts?
Room size isn't what determines how many watts he needs, it's the power needs of the speakers he owns.

Sure he may have got away with a smaller set of bookshelf speakers if the room isn't large (it looks like a decent sized living room loosely based on the pics anyway), but he has bought the ones he has! I guess one other option instead of mono-blocking with a 2nd amp, would be to downsize the speakers to a set easier to drive, but it seems like both he and the mrs are very happy with them.

I don't think you can really have speakers that are too big for a room, sure they may be bigger than needed, but never too big (other than aesthetics really). You can however have speakers that are too small to fill a room.
The volume will be determined by the size of the room(distance from speaker to lughole) , the audio power and the sensitivity of the speakers in dB/W.
Surely physically small speakers of adequate wattage will 'fill a room', albeit with maybe limited bass.

Do people actually know what their real listening actually peaks at in terms of watts?
Are we paying an awful lot for 'headroom'?

I've got a 70W/ch amp here, I've actually not got much idea how far away it is from clipping when I'm using it as I normally do.

Personally if I had 4 figure sums to spend on amps and speakers, I'd be looking at active crossovers and multi-amps per speaker.
Or I'd at least want to listen to that kind of system before spending.
The real thing, live, of course tends to be one amp per instrument?


Blowing thousands while sticking to the same old stereo amp, long cable, passive crossover, speakers architecture seems a little blinkered?

Harry Flashman

Original Poster:

19,863 posts

248 months

Thursday 6th April 2023
quotequote all
I tend to agree on the headroom point, as I don't listen at very high volumes. My problem is not volume, nor "filling the room". It's a 6m x 6m living room, with 3.7m ceilings, dominated by a big bay window.

The issue was meaningful bass at low volumes - I listen low in the evenings as despite being in the third floor, noise gets funnelled up the main staircase. At high volumes, the bass that the NAD C298 delivers is more than adequate. And on the rare occasions that I play music at high volumes, the sub can simply be dialled down in the app.

So whilst bi-amping sounds like fun, it probably isn't necessary now that I have integrated the sub so well into the system. But I shall be buying another amp on the 14 day return window and trying it out ,as, well, why not? Good to see which solution (bi-amping or sub) works better.

What I think is clear from everyone's posts is that hifi is a personal thing, and one person's solution may not work or be suitable for someone else. I am an electronic music person mostly, although I tend to listen to most main genres everything apart from jazz. When listening to electronic music, with its frequently low and fast bass, the little sub does great work (it doesn't sound as if any bass is coming from it, you focus on the soundstage and the main speakers completely). It plays to my preferences for that sort of music.

Yet on much "classic" classical music (as opposed to, say, a Hans Zimmer score) the system sounds a little heavy handed unless I switch off the sub, and I bet bi-amping would be better. Yet on this setup, you can switch off the sub in BluOs, which immediately switches off the crossover and directs all of the amp's output to the full range of the floorstanders as if the sub weren't there.

Technology has come a long way, and I like it! The journey continues.

I am a music person, rather than a hifi person. What this has all meant is that I am back to spending hours exploring new music, something I had largely ceased doing when we Sonos'd the whole house and I put my old system into the loft/repurposed the PMC speakers for AV. I am loving a return to hifi, for the sake of the music, rather than for the sake of the system.

I am really appreciating the advice and opinions on this thread, by the way. Thank you!



Edited by Harry Flashman on Thursday 6th April 09:14

AdamV12V

5,124 posts

183 months

Thursday 6th April 2023
quotequote all
Harry Flashman said:
I tend to agree on the headroom point, as I don't listen at very high volumes. My problem is not volume, nor "filling the room". It's a 6m x 6m living room, with 3.7m ceilings, dominated by a big bay window.

The issue was meaningful bass at low volumes - I listen low in the evenings as despite being in the third floor, noise gets funnelled up the main staircase. At high volumes, the bass that the NAD C298 delivers is more than adequate. And on the rare occasions that I play music at high volumes, the sub can simply be dialled down in the app.

So whilst bi-amping sounds like fun, it probably isn't necessary now that I have integrated the sub so well into the system. But I shall be buying another amp on the 14 day return window and trying it out ,as, well, why not? Good to see which solution (bi-amping or sub) works better.

What I think is clear from everyone's posts is that hifi is a personal thing, and one person's solution may not work or be suitable for someone else. I am an electronic music person mostly, although I tend to listen to most main genres everything apart from jazz. When listening to electronic music, with its frequently low and fast bass, the little sub does great work (it doesn't sound as if any bass is coming from it, you focus on the soundstage and the main speakers completely). It plays to my preferences for that sort of music.

Yet on much "classic" classical music (as opposed to, say, a Hans Zimmer score) the system sounds a little heavy handed unless I switch off the sub, and I bet bi-amping would be better. Yet on this setup, you can switch off the sub in BluOs, which immediately switches off the crossover and directs all of the amp's output to the full range of the floorstanders as if the sub weren't there.

Technology has come a long way, and I like it! The journey continues.

I am a music person, rather than a hifi person. What this has all meant is that I am back to spending hours exploring new music, something I had largely ceased doing when we Sonos'd the whole house and I put my old system into the loft/repurposed the PMC speakers for AV. I am loving a return to hifi, for the sake of the music, rather than for the sake of the system.

I am really appreciating the advice and opinions on this thread, by the way. Thank you!
A great post Harry...

I totally agree that HiFi is very personal thing and very subjective. What is enough for one person falls way short on expectations for another, or may be completely OTT for a third person. Very much like cars really! wink

Your room is large, especially with those very very high ceilings it's actually a huge volume to fill with sound. You will definitely feel the grunt of additional power in amps to grip and drive the speakers properly.

Do try both bi-amping and mono blocking though, with two of those NAD amps both options are available to you. Be sure you know the difference and how to setup and cable up each. I tried both on my way to my current setup, initially by purchasing a 2nd X-Power which like your NAD can be switched to do either. For me at least, mono blocking was vastly superior to bi-amping, and I think given your setup and issues with bass it will be for you too, but do try both and see for yourself which you prefer.

Sounds like we have similar tastes in music too, electronica first and foremost for me too, but largely I can listen to anything that's good, especially if it is well mastered and recorded. Having a superb Hifi really does let you appreciate a wider range of music for sure. Being a fan of electronica I totally understand that you want tight punchy controlled bass even at lower volumes, its not good having to turn it up loud to get the bass you want. Extra power will definitely boost the sound in this way.


Edited by AdamV12V on Thursday 6th April 12:01

RSTurboPaul

11,185 posts

264 months

Thursday 6th April 2023
quotequote all
Harry Flashman said:
...

The issue was meaningful bass at low volumes - I listen low in the evenings as despite being in the third floor, noise gets funnelled up the main staircase. At high volumes, the bass that the NAD C298 delivers is more than adequate. And on the rare occasions that I play music at high volumes, the sub can simply be dialled down in the app.

...
This sounds like an EQ issue to me.

Audyssey on my AVR has the ability to compress dynamic range, so one can listen to a film at an even volume late at night without sudden explosions frightening the horses, and it can also boost the bass range at lower volumes so that the listener can still hear them and it sounds balanced with the rest of the music (ref: Fletcher Munson curves showing higher bass volume needed compared to treble, as I understand it).

The latter reduces in effect the higher the main volume goes, such that at 0/Reference there is no bass range boost applied and it therefore sounds balanced at all volumes.

I'm not convinced that adding amps and headroom and throwing ££££ at the problem is going to fix it if there is not the ability to dynamically EQ the bass range with reference to the Main Volume setting.

Does DIRAC not have that ability or is its main/only focus to deliver a 'flat' output across the range?

Edited by RSTurboPaul on Thursday 6th April 12:37

OutInTheShed

8,867 posts

32 months

Thursday 6th April 2023
quotequote all
Harry Flashman said:
I tend to agree on the headroom point, as I don't listen at very high volumes. My problem is not volume, nor "filling the room". It's a 6m x 6m living room, with 3.7m ceilings, dominated by a big bay window.

The issue was meaningful bass at low volumes - I listen low in the evenings as despite being in the third floor, noise gets funnelled up the main staircase. At high volumes, the bass that the NAD C298 delivers is more than adequate. And on the rare occasions that I play music at high volumes, the sub can simply be dialled down in the app.

So whilst bi-amping sounds like fun, it probably isn't necessary now that I have integrated the sub so well into the system. But I shall be buying another amp on the 14 day return window and trying it out ,as, well, why not? Good to see which solution (bi-amping or sub) works better.

What I think is clear from everyone's posts is that hifi is a personal thing, and one person's solution may not work or be suitable for someone else. I am an electronic music person mostly, although I tend to listen to most main genres everything apart from jazz. When listening to electronic music, with its frequently low and fast bass, the little sub does great work (it doesn't sound as if any bass is coming from it, you focus on the soundstage and the main speakers completely). It plays to my preferences for that sort of music.

Yet on much "classic" classical music (as opposed to, say, a Hans Zimmer score) the system sounds a little heavy handed unless I switch off the sub, and I bet bi-amping would be better. Yet on this setup, you can switch off the sub in BluOs, which immediately switches off the crossover and directs all of the amp's output to the full range of the floorstanders as if the sub weren't there.

Technology has come a long way, and I like it! The journey continues.

I am a music person, rather than a hifi person. What this has all meant is that I am back to spending hours exploring new music, something I had largely ceased doing when we Sonos'd the whole house and I put my old system into the loft/repurposed the PMC speakers for AV. I am loving a return to hifi, for the sake of the music, rather than for the sake of the system.

I am really appreciating the advice and opinions on this thread, by the way. Thank you!



Edited by Harry Flashman on Thursday 6th April 09:14

Interesting post.
We're similar in some ways.
Different in others.
I'm interested in the tech, my wife is not but is critical about the music.
A lot of jazz and classical, some choral for her. For me it's rock, jazz, instrumental mostly.

Not really spent much on HiFi yet, until 2 years ago most listening time was in our cars.
Now have a house where we can turn it up a bit.
We're just using some mid-size Wharfedale and Kef speakers at the moment, and a pair of Gale bookshelf speakers in the kitchen.
So although I understand a lot of the technology, having worked in instrumentation etc, I'm not yet that familiar with high end systems,

But what you are describing, the relative strength of the bass varying at different volume levels, (if that's a fair summary?) is likely more about your speakers and your perception than the amp?
I'd expect that amp to be basically relentlessly linear until it starts running out of power?
And it's an Amp capable of delivering a lot of Amps...

Do you have impedance plots for the speakers? Notionally 4ohm, they could be quite demanding?
One perhaps starts to realise that if there's any dip in the impedance, the speaker cable might start to 'matter' when people start wanting 'grip' on the speakers (which perhaps translates to damping factor, output impedance, the impedance the speaker 'sees'.....?)
So if you try 'monobloc' are we talking about moving the power amps close to the speakers, paralleling two channels and short speaker cables?


RSTurboPaul

11,185 posts

264 months

Thursday 6th April 2023
quotequote all
OutInTheShed said:
...
One perhaps starts to realise that if there's any dip in the impedance, the speaker cable might start to 'matter' when people start wanting 'grip' on the speakers (which perhaps translates to damping factor, output impedance, the impedance the speaker 'sees'.....?)
So if you try 'monobloc' are we talking about moving the power amps close to the speakers, paralleling two channels and short speaker cables?
Is there any empirical evidence re: cable options?

Or is that all 'audiophile' nonsense? tongue out lol

Harry Flashman

Original Poster:

19,863 posts

248 months

Thursday 6th April 2023
quotequote all
Some great posts, chaps.

For me, the low volume bass problem has been solved by the little sub. It simply has more capability at sub bass frequencies than the speakers do, no matter how hard they are driven. Thes specs of each reveal this - no matter how driven, my speakers can't get down to 23Hz. And I like sub bass, a lot! I have set the sub's crossover at 50Hz with a nice, shallow curve to roll off from there. Floorstanders' crossover starts at 50Hz, also on a nice roll in curve - so they are doing slightly different things with a tiny bit of overlap.

You can absolutely boost the bass on DIRAC with the speakers. Doing so did not deliver the sub bass I wanted at lower volumes from the speakers, likely for the reasons above. So it will be a combination of the speakers' frequency floor, room/positioning, and power to drive bass frequencies. Lots of ways to skin that cat, but a small, fast sub seemed easiest, especially as a combination of BluOs, DIRAC and SVS' own sub app make integration an absolute doddle.

OutInTheShed

8,867 posts

32 months

Thursday 6th April 2023
quotequote all
RSTurboPaul said:
Is there any empirical evidence re: cable options?

Or is that all 'audiophile' nonsense? tongue out lol
I think a lot of 'audiophile nonsense' has a grain of truth in it, often taken out of context, and often extrapolated to absurd levels.

My feeling on cables and crossovers is it seems a bit potty to spend loads of time and money developing or buying a slightly better amplifier, then isolate it from the load with an inductor, add an undefined length of cable then a speaker different from the one the amp was developed for, with a bunch of reactive components between the driver coil and the cable.
It just seems far more elegant to have one power amp per driver coil.

Also it potentially means less power amps can be used, if the peak audio waveform is 10V of Bass with 10V of Treble superposed on it, you need a 20V amp instead of two 10V amps. A 20V amp is 4x the power of a 10V amp.

But the world of HiFi is rooted in the tradition of expensive boxes labelled 'amplifier' and separate expensive boxes labelled 'speaker'.
And that tradition is highly developed, with 60+ years of lots of clever people working on it.

Idle musings really, I'm mostly happy with what I have right now, trying to get it all to work together with some sort of server/library/jukebox malarkey is my current mission.

AdamV12V

5,124 posts

183 months

Thursday 6th April 2023
quotequote all
There are indeed many other reasons you maybe experiencing lack of bass, but given its predomentely at low volumes would lead me to believe what I had proposed above is the most likely to remedy.

Other factors could be
  • quality of speaker cables, or interconnects. I wouldn't advocate spending a fortune on either, but equally buying decent quality cables of a grade befitting of the components and speakers you have bought would be advised. Certainly avoid and replace any budget bell wire cables still sold online and in shops, especially for the speaker cable. Keep all cables as short as is reasonably feasible, and keep speaker cables of equal length to each other.
  • hard floors and a lack of soft furnishings. No idea what else you have in the room, but a hard floor and hard furnishings will always enhance the higher frequencies than you would hear with a room with carpet and lots of soft furnishings. That said I have a hardwood floor too and my bass is strong and punchy, but I do have other soft furnishings in the room in the form of two large fabric sofa's with cushions. Providing the room doesn't make your voice sound hollow or have any echoing then you should be OK. There are plenty of acoustic materials you can introduce to help with a harsh room, but I don't use any of those myself mainly because I could not gel with their looks. If nothing else then a rug in the middle of the room will always help.
  • I would personally turn off any and all electronic processing features such as dirac, and I would remove the sub. Sure these things may mask or compensate for a problem, but before moving to any of those I would get the basics solid and sounding right. Once you have a good sounding system, then maybe introduce and tinker with such tech to give the final level of tuning if you feel its needed. Using it too early could actually be introducing problems, rather than curing them.
OutInTheShed said:
It just seems far more elegant to have one power amp per driver coil.

Also it potentially means less power amps can be used, if the peak audio waveform is 10V of Bass with 10V of Treble superposed on it, you need a 20V amp instead of two 10V amps. A 20V amp is 4x the power of a 10V amp.
Totally agree with this^^

I would tend to poke a bit more power into the bass speaker pair, but only by using amps with the same tonal output - i.e. from the same manufacturer, but you certainly could reduce the power overall with 4 monoblock amps bi-amped.

OutInTheShed said:
So if you try 'monobloc' are we talking about moving the power amps close to the speakers, paralleling two channels and short speaker cables?
No, and yes! wink

Monobloc in its simpliiest form is one mono (or bridged into mono) power amp per speaker. So one amp for the right channel and one for the left channel.

Bi-Amping is using two stereo amps one to control R&L high frequency drivers in the speaker and one stereo amp to drive the R&L bass drivers. This can only be done if the speakers have two sets of inputs.

Finally the ultimate solution is to use use 4 mono amps one for each of HF-L, HF-R, LF-L, LF-R - again only if the speakers have two sets of speaker wire inputs. Some speakers actually have 3 sets of inputs, so would enable 6 mono power amps, but now we really are into top end budget stuff!

Speaker cable being short isn't a essential for any of these setups, but it is however always preferable.

--

Of course all of the above requires skill and knowledge to get the best sound to suit your own ears, not to mention time, patience and money en-route!

These days theres a lot to be said for say a set of KEF LS60 wireless active speakers, where a single manufacture has paired up amps and speakers into a single purchase piece of tech. They pair them to precisely perform well with each other, within the limit of the budget they set to sell the units for. Being wireless they integrate directly with a phone, tv or steamer or service such as roon. They have a lot of appeal, which is why they sell well, but ultimately if you truely want to get the very best sound traditional hifi is still the way to go, but the gap closes every year.

Edited by AdamV12V on Thursday 6th April 19:50

Harry Flashman

Original Poster:

19,863 posts

248 months

Thursday 6th April 2023
quotequote all
NDA of this parish has the LS60s, and loves them.

I'm not quite there yet as I like being able to swap an element to change things. But he is a music professional, or was, and his hifi journey has ended with the KEFs.

RSTurboPaul

11,185 posts

264 months

Thursday 6th April 2023
quotequote all
I will repeat my earlier post wink and ask if there is any empirical evidence as to benefits (or not) of different cabling - other than obvious things like having a wire with a cross-section of conductive material large enough to cope with the power being put through it, so it does not melt or glow like a light bulb tongue out.


And, likewise, is there any empirical evidence as to length of cables making any actual difference, given that the speed of an electrical signal in a wire approaches the speed of light in a vacuum?

https://www.wtamu.edu/~cbaird/sq/2014/02/19/what-i...

Harry Flashman

Original Poster:

19,863 posts

248 months

Thursday 6th April 2023
quotequote all
RSTurboPaul said:
I will repeat my earlier post wink and ask if there is any empirical evidence as to benefits (or not) of different cabling - other than obvious things like having a wire with a cross-section of conductive material large enough to cope with the power being put through it, so it does not melt or glow like a light bulb tongue out.


And, likewise, is there any empirical evidence as to length of cables making any actual difference, given that the speed of an electrical signal in a wire approaches the speed of light in a vacuum?

https://www.wtamu.edu/~cbaird/sq/2014/02/19/what-i...
I tend to agree. I have (the basic, not insane) Chord interconnects and QED cable, all at equal lengths.

RSTurboPaul

11,185 posts

264 months

Thursday 6th April 2023
quotequote all
Harry Flashman said:
RSTurboPaul said:
I will repeat my earlier post wink and ask if there is any empirical evidence as to benefits (or not) of different cabling - other than obvious things like having a wire with a cross-section of conductive material large enough to cope with the power being put through it, so it does not melt or glow like a light bulb tongue out.


And, likewise, is there any empirical evidence as to length of cables making any actual difference, given that the speed of an electrical signal in a wire approaches the speed of light in a vacuum?

https://www.wtamu.edu/~cbaird/sq/2014/02/19/what-i...
I tend to agree. I have (the basic, not insane) Chord interconnects and QED cable, all at equal lengths.
I need to post a picture of the nest of snakes that is my variety of cheap cables tangled up behind the sofa tongue out

OutInTheShed

8,867 posts

32 months

Thursday 6th April 2023
quotequote all
AdamV12V said:
No, and yes! wink

Monobloc in its simpliiest form is one mono (or bridged into mono) power amp per speaker. So one amp for the right channel and one for the left channel.

...]
My understanding of 'monobloc' was basically a single power amp in a box with its own PSU etc.
My understanding of 'bridged mono' amps is instead of having a single amp driving the speaker relative to 'gnd', you have effectively a non-inverting amp driving the red terminal and an inverting amp driving the black terminal. So the voltage swing can be doubled. Handy in cars where the supply is 12V.

Somebody upthread was suggesting using two of these amps as monoblocks. As the speakers are 4ohm, I would not have thought bridging would be favoured because that would mean each amp only sees 2 ohms to ground? So I wondered if parallel amps were being suggested to get more current or lower output impedance. I would think that's not trivial if it's not designed in.

So I am in the dark as to where monobloc(k)ing two of these amps is likely to be helpful.

paralla

3,821 posts

141 months

Thursday 6th April 2023
quotequote all
We recently got a new hand knotted rug, it’s 270cm x 380cm x 2cm Chinese Silk & New Zealand Wool, it weighs 64kg and covers an engineered oak floor.

Once it was in place I did a full Audissey setup of the AV amp because the rug was sure to have changed the acoustic properties of the room.




AdamV12V

5,124 posts

183 months

Thursday 6th April 2023
quotequote all
OutInTheShed said:
AdamV12V said:
No, and yes! wink

Monobloc in its simpliiest form is one mono (or bridged into mono) power amp per speaker. So one amp for the right channel and one for the left channel.

...]
My understanding of 'monobloc' was basically a single power amp in a box with its own PSU etc.
My understanding of 'bridged mono' amps is instead of having a single amp driving the speaker relative to 'gnd', you have effectively a non-inverting amp driving the red terminal and an inverting amp driving the black terminal. So the voltage swing can be doubled. Handy in cars where the supply is 12V.

Somebody upthread was suggesting using two of these amps as monoblocks. As the speakers are 4ohm, I would not have thought bridging would be favoured because that would mean each amp only sees 2 ohms to ground? So I wondered if parallel amps were being suggested to get more current or lower output impedance. I would think that's not trivial if it's not designed in.

So I am in the dark as to where monobloc(k)ing two of these amps is likely to be helpful.
The NAD C298 can be run in stereo mode driving 340W @ 4ohms in a pair of speakers or bridged into Mono mode giving 1100W @ 4Ohm into one single speaker. There is a switch on the back of the amp to do this, and you connect the speakers to the Right +ve and Left -ve terminals. A 2nd NAD C298 could be purchased and also set into Mono mode, thus giving one mono amp per speaker, each driving 1100W into it. It is basically the same in cars yes, "bridging" is a term that simply means combining both channels of a stereo amp into a single mono channel.

See specs https://nadelectronics.com/product/c298-stereo-pow...



More expensive dedicated mono amps are a single high power mono amp by design from the ground up, but the result is basically the same.
Yes single top end power amps often come with their own dedicated PSU, but that's by no means part of the definition of what a mono block amp is.

Read one of the many definitions on google, rather than me nailing down just one

https://www.google.com/search?q=what+is+a+monobloc...


Edited by AdamV12V on Thursday 6th April 21:02