NAD C 298 Power Amplifier With Purifi Eigentakt Amplification

[pogo]

I highly doubt such a modern amp use a "mechanical pot" for gain control.

But it looks like it, as has been said before:
'Variable gain added a bit of THD and channel imbalance on the C298.'

 

[ihvar]

But it looks like it, as has been said before:
'Variable gain added a bit of THD and channel imbalance on the C298.'

I have RME ADI-2 DAC as preamp, so in fixed gain a comfort listening level is at -5dbU.
What would you recommend in my case - using RME at -5 dbU at fixed gain or using RME at +5+7 dBU but with variable gain on NAD C 298?

 

[ebslo]

I have RME ADI-2 DAC as preamp, so in fixed gain a comfort listening level is at -5dbU.
What would you recommend in my case - using RME at -5 dbU at fixed gain or using RME at +5+7 dBU but with variable gain on NAD C 298?

There was a fair bit of discussion of gain adjustment upthread, but in the end it depends what you're trying to optimize for. I set mine such that a digital full scale sine wave would result in the measured max dynamic power into a 4Ohm load. The effect of the adjustment on system noise was minimal, with the detection distance for audible tweeter hiss staying within the 3 to 5 inches range, and no audible noise from the other drivers.

 

[peng]

But it looks like it, as has been said before:
'Variable gain added a bit of THD and channel imbalance on the C298.'

A non mechanical pot (IC types) can also introduce a bit of THD, noise and channel imbalance. We have seen channel imbalance on many devices measured on ASR haven't we?

 

[pogo]

I prefer the discrete switchable design. This should cause fewer problems

 

[eyesofra]

Hi guys,
I've been reading through this thread and now have an oppurtunity to get a C298 used around 9 months old. I'm aware the early amps had some teething issues. Can you advise if thesehave been addressed and what to look-out for when one is buying a used one pls ?

 

[Norway]

Finally spoke to NAD and have a thorough update. Instead of replying to my email they called me and were very polite and helpful.

There is indeed a firmware problem with some early C298 units. Luckily it’s not a hardware problem. It does not affect all units within a certain serial number range, so everyone just needs to keep an eye on their unit for malfunction.

As suspected, the basis of the problem is a false power protect trigger.

How to check your firmware version:

In operating mode: press and hold the power button for between 5 and 10 seconds. Once you let go, the power light should flash once, then the bridge mode light will flash a certain number of times. Early units like mine (both my faulty unit and the new replacement) flash seven times to indicate v1.07. The fixed firmware is v1.08, which would of course mean eight flashes.

NAD HQ sent out a service bulletin in late December about this issue. All distributors should know about the problem via the service bulletin. Not all service centers will have seen this problem before and may not be aware of the problem.

Any NAD service center should be able to perform this firmware update, but they will need a physical firmware update kit specific to this job, so if you contact them they will need some lead time to get the kit if they haven’t performed this service before.

Personally, I already sent back my faulty first unit but will keep vigilant on this second one and get it serviced if anything comes up. This will be covered by NAD’s warranty for two years (at least that’s how long the warranty is in the US).

Just received two new units. They both flash 4 times… not 8!.?

 

[nothingman]

I haven’t seen this myself, but if by 4 flashes you mean you are really seeing 2 flashes, then a brief pause, then 2 more flashes, then I think that means you have v2.2.

 

[Norway]

I haven’t seen this myself, but if by 4 flashes you mean you are really seeing 2 flashes, then a brief pause, then 2 more flashes, then I think that means you have v2.2.

No it flashes 4 times with no pause.

 

[nothingman]

No it flashes 4 times with no pause.

Ok then. Best to confirm the process with NAD then.

 

[ihvar]

I really love my C298, but I doubt that ABX with your current amp would reveal much difference. But the opportunity to use XLR connections could have an audible impact, I suppose.

I'd probably be looking first at upgrading the speakers.

Switched from RCA to XLR and the sound became more full in high frequencies. Also upgraded to Furutech FP-202(R) bananas )

 

[Mehdiem]

I'm planning to buy C298. I read through this thread and I see a few complaints about (1) humming noise (2) auto-shutoff (3) variable gain creating imbalance.

I am wondering if these issues (1) & (2) are unit-specific issues, or apply to all units?

With respect to issue (3) variable gain, can you elaborate on how this issue occurs? Is it only for when you use it as a monoblock, or it even occurs when you use it as a stereo amp? How concerning this issue is? This would be my first Purifi amp, so I don't want to get something troublesome. I will be using RME ADI-2 as my pre-amp/DAC.

Do you think buying this amp would be a waste of money (considering its imperfections) and whether you would go with VTV or any other brands instead?

 

[tparm]

I'm planning to buy C298. I read through this thread and I see a few complaints about (1) humming noise (2) auto-shutoff (3) variable gain creating imbalance.

I am wondering if these issues (1) & (2) are unit-specific issues, or apply to all units?

With respect to issue (3) variable gain, can you elaborate on how this issue occurs? Is it only for when you use it as a monoblock, or it even occurs when you use it as a stereo amp? How concerning this issue is? This would be my first Purifi amp, so I don't want to get something troublesome. I will be using RME ADI-2 as my pre-amp/DAC.

Do you think buying this amp would be a waste of money (considering its imperfections) and whether you would go with VTV or any other brands instead?

I am glad to speak of my experience with this amp. Mine is dead silent, I haven’t experienced hum in my system (AVM 70, balanced connection, LSiM speakers) of my friends dedicated two channel system (esoteric, balanced connection, totem speakers). I also use a trigger cable and not signal sensing for on/off, but I have not had mine shit down at any time. Lastly, I use it in stereo configuration with gain fixed as I believe you would in your system so variable gain is moot point.

So far, over a month in, it has performed very well, I love the sound and it plays clean at high levels which lost amps do but sounds great a moderate levels too. I can’t speak to VTV amps but I do have a connection for good pricing on the NAD if you message me I am glad to pass along.

 

[jamesoco]

I have both the C298 and the VTV. I'm sending the C298 back and keeping the VTV.
The C298 is a great amp but the difference in sound between it and the VTV on my Magnepan 3.7i's is very little.
I felt the VTV had better soundstage and presence and the C298 had a bit more forward high's.
I'm using the stock hypex buffer and plan on experimenting with others in future.
I don't need the variable gain of the NAD and a 3 channel VTV cost less than the stereo C298.
You can't go wrong with either amp in my opinion.
Warren at VTV has been excellent.

 

[Mehdiem]

I have both the C298 and the VTV. I'm sending the C298 back and keeping the VTV.
The C298 is a great amp but the difference in sound between it and the VTV on my Magnepan 3.7i's is very little.
I felt the VTV had better soundstage and presence and the C298 had a bit more forward high's.
I'm using the stock hypex buffer and plan on experimenting with others in future.
I don't need the variable gain of the NAD and a 3 channel VTV cost less than the stereo C298.
You can't go wrong with either amp in my opinion.
Warren at VTV has been excellent.

What exact VTV configuration would be equivalent to C298? Do you mind sharing the link? When you say experiment in future, do you mean reconfigure it yourself?

 

[tparm]

What exact VTV configuration would be equivalent to C298? Do you mind sharing the link? When you say experiment in future, do you mean reconfigure it yourself?

VTV AMPLIFIER Stereo Purifi Audio 1ET400A Amplifier | VTV Amplifier

I agree with @jamesoco that you really can't go wrong either way. The real question which input buffer on the VTV provides the sound you are going for? I spoke with Warren too and for some reason he and I couldn't get on the same page, I felt like I was bugging him and my (2) questions weren't complex.... I have been of the camp for many years that class AB amps really don't sound much different one from another (not no difference, but very little). With Purifi modules requiring an input buffer things change a bit. I was comfortable with both the reports I got back from a few people that had herd the C298 before I bought it and also knew I could return it if I wasn't happy with it. Alas, I am.

And yes, you can switch out the buffer boards of the VTV amps yourself with not too much effort.

 

[jamesoco]

VTV AMPLIFIER Stereo Purifi Audio 1ET400A Amplifier | VTV Amplifier

The C298 is rated at 340 watts in 4 ohms and the VTV is rated at 425 watts in to 4 ohms. They both have the Purifi technology in them. NAD licensed the Purifi tech and built their own implementation (which could explain the power difference) and VTV buys the Purifi 1ET400A modules and installs them in a case with a Hypex power supply and Input Buffer board.

VTV also sells their own Input Buffer board that allows you to choose one of 7 customer OpAmps. Warren suggested I start with the stock Input Buffer, get use to it and then try others. He's very cool about letting you update later and send back the old Input Buffer. It's not a difficult thing to do, just requires disconnecting some cables, etc. and installing a new board.

Here's a video on how to do that.

 

[SIY]

VTV also sells their own Input Buffer board that allows you to choose one of 7 customer OpAmps. Warren suggested I start with the stock Input Buffer, get used to it and then try others.

Get used to it?

 

[ihvar]

I'm planning to buy C298. I read through this thread and I see a few complaints about (1) humming noise (2) auto-shutoff (3) variable gain creating imbalance.

I am wondering if these issues (1) & (2) are unit-specific issues, or apply to all units?

With respect to issue (3) variable gain, can you elaborate on how this issue occurs? Is it only for when you use it as a monoblock, or it even occurs when you use it as a stereo amp? How concerning this issue is? This would be my first Purifi amp, so I don't want to get something troublesome. I will be using RME ADI-2 as my pre-amp/DAC.

Do you think buying this amp would be a waste of money (considering its imperfections) and whether you would go with VTV or any other brands instead?

I bought NAD C 298 a month ago and using it with RME ADI-2 DAC FS. Sound is crystal clear and powerful at once.
It doesn't have problems you're speaking about. Everything works fine, I suggest you to buy good banana connectors like FURUTECH FP-202(R) for full experience and Vovox XLR cables

 

[ehowarth]

I see a few complaints about (1) humming noise (2) auto-shutoff (3) variable gain creating imbalance.

1. Dead silent. Warranty repair otherwise.

2. Auto shutoff is configurable. I use it. Having very sensitive speakers I wish the lowest setting let me play up to 6 dB quieter for the atypical use case of very quiet background listening.

3. Use INPUT SELECT switch to manage audio output level.
• FIX: Audio output level is fixed. The C 298 becomes like a basic
amplifier with audio output level controlled by an external device.
• VAR: Audio output level can be adjusted using the INPUT LEVEL
control knob.