NAD C268 Power Amplifier Review

[Jimbob54]

Corrected.

Now if we could do something about all the old knob twiddlers around here we would be OK.

 

[rodtor]

The same amplifier should be in C368 integrated?

It should be similar, or at least NAD must think so, as they propose that the C268 be paired with the C368 in bridged mode.

 

[Hugo9000]

You engage the rarely used and massively un-PC "bust" mode at one point, you saucy devil.

Bust Mode:

 

[Jimbob54]

Bust Mode:

Well that really will agitate the old knob twiddlers!

 

[Bear123]

Hhmmm... what is better at $900 ?

Other than bridged, how about a 7 channel Denon AVR for $500. (X3500). Way more power and features that result in far better sound quality.

Otherwise, the Outlaw M2200...2 for $700, 3 for $999, also with a lot more power outside of bridged mode.

Also the Monolith 2 channel is $999 with far more power and better performance.

 

[McFly]

@amirm you do HF switching noise test?

 

[GXAlan]

This also shows that a recommended Class D amp doesn't quite perform as well as an Accuphase Class AB integrated amp. You gain a lot of performance for the money, of course, but it does show that if you already have a good Class AB amp, it's not that critical to switch to a new-fangled digital amp.

 

[digicidal]

For $600, you can go the monoblock route with a pair of Emotiva PA-1’s, Would like to see it measured.

I'd love to see it measured as well. I love mine... nice and simple, cheap and cool, and very compact and light. Sure there are some drawbacks (theoretically) over a AB topology... but I forget all about those when I pick one of the PA-1's up!

I could run a marathon carrying 3 of those... but I've blown my back out just pulling my XPA-3 out of the rack to check connections.

Generally speaking however, the IcePower modules are a bit behind... so I'd guess the PA-1 wouldn't be any better (re Nad C268) - likely a bit worse in some areas. On the other hand... I apparently don't listen critically to any of those areas. LOL.

 

[restorer-john]

Good review @amirm

So what's with the blue negative binding posts? Is that some new EU mandated directive I don't know about or is it an indication they are not actually sitting at chassis earth. Notice the BTL connection- that means one amp is out of phase/polarity with the other in normal operation- BTL is taken from the two hots otherwise. (they also did that with the old 2200 to maximize power supply use)

PS. That also explains your strange crosstalk result. It's actually an artificial "near state of the art" figure in mid frequencies because the common, but inverted signal is simply cancelling the signal in the other channel.

 

[amirm]

@amirm you do HF switching noise test?

No, forgot. Sorry.

 

[amirm]

PS. That also explains your strange crosstalk result.

Ah, makes sense now.

 

[Doodski]

Good review @amirm

So what's with the blue negative binding posts? Is that some new EU mandated directive I don't know about or is it an indication they are not actually sitting at chassis earth. Notice the BTL connection- that means one amp is out of phase with the other in normal operation- BTL is taken from the two hots otherwise. (they did that with the old 2200)

View attachment 70392

PS. That also explains your strange crosstalk result.

I googled those blue binding posts and found no details regarding a colour code or anything like that. I suspect it is a off colour simply to get the users attention.

 

[restorer-john]

I googled those blue binding posts and found no details regarding a colour code or anything like that. I suspect it is a off colour simply to get the users attention.

It's likely to mean neutral, but not actual earth (or 0v). For multi speaker installations and speaker switch panels, especially ones that switch only the hots, you'd run into trouble with shorted amplifier outputs otherwise.

 

[Blumlein 88]

It's likely to mean neutral, but not actual earth (or 0v). For multi speaker installations and speaker switch panels, especially ones that switch only the hots, you'd run into trouble with shorted amplifier outputs otherwise.

I wish there were some standard for such amplifiers. Labeling amps red and black has caused plenty of troubles when they really are differential outputs. Like when people use the speaker input to a subwoofer from one of these. Ouch!

 

[restorer-john]

If blue draws attention to the "negative" not being or possibly not at 0V/chassis, that's good thing. Perhaps it is a new defacto standard? Personally, I like it.

 

[RayDunzl]

So what's with the blue negative binding posts?

My 15 year old Krells, with differential outputs have red and blue for the colors.

Monoblock below, one channel, with facility for biwiring

My other two amps, even older, just have red and black.

 

[restorer-john]

My 15 year old Krells, with differential outputs have red and blue for the colors.

Your Krells aren't bridged, but they do float the negative above and not connected to the chassis.

Funny, I've seen blue (-) terminals but never really considered why. Now we know. You learn something every day.

 

[restorer-john]

Ray, are you sure that mains cable is thick enough?

Looks like it could do with an upgrade...

 

[Music1969]

Amplifier Bridged Mode Performance

Hi Amir, can you measure bridged mode into 4 ohms?

And you usually show the switching frequency for Class D amps?

 

[RayDunzl]

Your Krells aren't bridged, but they do float the negative above and not connected to the chassis.

The output is differential, like the XLR (or CAST) that feeds them.

There is no unbalanced input.

+ and - output terminals giving + and - wave.

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Maybe Schematic: http://www.tubebbs.com/thread-266201-1-1.html