Review and Measurements of NAD C 320BEE PWR Amplifier

[TimW]

I just picked one of these up for next to nothing because it wasn't working. The main power supply caps had been replaced but for whatever reason the new Rubycon ones had popped and leaked all over the power supply board. According to some forum posts I've seen these amps often quit working due to bad JH brand caps. So I replaced all six of the electrolytic caps in the power supply. The old JH ones weren't far off of spec as far as capacitance goes but their ESR was pretty high. Also had to replace two fuses, connector contacts that had corroded from the cap leakage, and three caps in the protection circuit that had been replaced with improper values.

The amp works like a charm now and sounds great. I couldn't hear much of a difference between connecting the DAC to the disc input or connecting directly to the main in. Hard to believe it's only a 67 watt amp. Keeping my fingers crossed that I solved the issue and I won't have more popped power supply caps on my hands.

 

[Wombat]

I just picked one of these up for next to nothing because it wasn't working. The main power supply caps had been replaced but for whatever reason the new Rubycon ones had popped and leaked all over the power supply board. According to some forum posts I've seen these amps often quit working due to bad JH brand caps. So I replaced all six of the electrolytic caps in the power supply. The old JH ones weren't far off of spec as far as capacitance goes but their ESR was pretty high. Also had to replace two fuses, connector contacts that had corroded from the cap leakage, and three caps in the protection circuit that had been replaced with improper values.

The amp works like a charm now and sounds great. I couldn't hear much of a difference between connecting the DAC to the disc input or connecting directly to the main in. Hard to believe it's only a 67 watt amp. Keeping my fingers crossed that I solved the issue and I won't have more popped power supply caps on my hands.

Fake Rubycons? They are all over Ebay.

 

[TimW]

Fake Rubycons? They are all over Ebay.

Quite possible. The guy who fixed it last often buys cheap ebay parts. And when I bought the new ones from Digi-Key they didn't stock any that matched the dimensions of the old ones.

 

[snowsurfer]

I think I'm gonna get one of these for my kitchen system (amp + ifi zen blue + q acoustics 2020s that were retired from my HT setup, where they were used as back channel speakers). Just waiting for a good deal on eBay.

 

[restorer-john]

Fake Rubycons? They are all over Ebay.

Totally. I have original Rubycon Black Gates here (ones I've had for decades and in OEM Japanese gear) and I'd love to post the finer details that can help people identify the real from the fake, but that information and detail will be used (eventually) by the counterfeiters...

At this stage, I can safely say, I haven't yet seen a genuine BG on EBay or even from the so-called NOS sellers. Even the guys supposedly "pulling" them from old gear (hint: they don't). It's a disaster as people are paying absolutely stupid money for capacitors they think are genuine and they aren't.

And no, don't ask me for the details. By all means post closeup pictures of any BG you like and I can identify if it's fake or not.

 

[Reddy]

I have tested the C320BEE for several month at the side of a topping D50. I only have used the end amplifier. The sound was not exceptional. One recapping has improved things and changing some resistors in certain points as well. However, the really great steps bringing improvements will be those in regarding the circuit, spots that are relevant concerning protection. Another improvement came from suppling the first stage with a regulated power supply. Having come to this point, one can tell with a smile that you can hear out the fred´s rectifiers.

Subjectively, the difference to the beginning is huge. Much more space, seperation, details, hall, depth and so on.

 

[Rifmon]

It's rated at the same power whether into 4 ohms or 8 ohms. Unusual.
Schematic available here.

View attachment 31524

I see this often in both new and vintage gear where there are either the same watts into 8 and 4 ohms, or just slightly higher. One such example is the Parasound NewClassic 200 Integrated Amplifier that has ratings at 110 watts into 8 and 4 ohms. I've been puzzled by this. I also was looking at a recapped vintage Nikko Alph II with 120 watts into 8 ohm but only slightly higher into 4. (I forget the exact amount). While I am in the market to upgrade from my HK 3490, I am avoiding amps with such ratings.

Can anyone explain why some new and vintage amps have such ratings as opposed to coming close to doubling wattage from 8 to 4 ohms?

 

[rwortman]

It's because the amp has enough voltage gain to produce XXX watts into 8 ohms but not enough safe current capability to double its current at the same voltage into 4 ohms. The designer lets or causes the voltage to drop into the lower load impedance. It's simply a design choice. All designs have compromises. The designer has to ask himself is it necessary to spec the output devices and heat sinking necessary to double the output into 4 ohms. Does the owner of the 4 ohm speaker demand twice the power as the owner of the 8 ohm speaker? How many of my potential buyers own or will own 4 ohm speakers? The answers determine the design.

 

[Rifmon]

Thanks. I guess that's why I see so many vintage amps that don't have ratings for 4 ohms or, if they do, the amount of wattage increase into 4 ohms is very small. Vintage speakers were pretty sensitive from what I've seen. My main speakers are 86 db in-room. I have hesitated to purchase a vintage amp despite some decent 8 ohm ratings. I would've pulled the trigger a few times on very nicely documented recapped vintage amps but didn't for this very reason.

 

[rwortman]

Are your speakers nominally 4 ohms? What has lead you to believe that you need an amp that doubles its power into 4 ohms? I ran an NAD power amp for years that was rated at 150wpc into 4 or 8 ohms to drive a pair of 4 ohm speakers and I never thought it was a problem. It had two voltage rails, one for 8 ohm loads and one for 4. It seems to me that whatever speakers you have, you need enough power to drive them and whether the amp halves, or doubles, or 1.5's its power into some other speaker is kind of irrelevant.

 

[Rifmon]

I must admit that I'm looking at the newer high current designs that boast of close to doubling the wattage as the resistance decreases. So since this is a feature that seems to be desirable, I am assuming it is something that my speakers may benefit from. The amount of watts recommended for my speakers are from 45 watts to 150 watts 300 watts peak. They are 8 ohms but according to the manufacture, the dip down to 6 ohms. However Amir reviewed similar speakers showing they go down lower closer to 4 ohms. I have the Sierra 2 EX and Amir reviewed the Ascend 2. So there may be differences between the two models' actual measurements. Between a possible lower ohms and the relative low speaker sensitivity of 86 db in-room, I guess I'm hesitant to buy a recapped fully restored vintage that doesn't measure higher watts into 4 ohms. I am not educated on electronics, power, resistance, volts watts, etc, so I am trying to peice this all together. I want to buy something that'll drive my speakers at least close to their potential.

BTW, my room is 15 deep, 20 wide and 8 ft high (ceilings) I site 12 feet from the speakers and listen from low to pretty loud volumes Possibly 97 db. But I've only used an iPhone app meter, not a good stand alone.

 

[th0m]

This was the first semi-serious amp that I bought in my late teens. I remember the pot started becoming "scratchy" after just a couple of months, but other than that it drove my old B&W 603 S3's quite well.

 

[EasyGuy]

I'm thinking about buying this one to try out. Does this NAD have audio sense function where it will turn on the amp automatically if it sense a signal? I hate to turn off and on amplifiers and that is important to me.

Also to bypass the pre-amp, do I just plug it in the "main in"?

 

[TimW]

I'm thinking about buying this one to try out. Does this NAD have audio sense function where it will turn on the amp automatically if it sense a signal? I hate to turn off and on amplifiers and that is important to me.

Also to bypass the pre-amp, do I just plug it in the "main in"?

No it does not have audio sense.

And yes, to bypass the preamp just remove the jumpers between pre-out and main-in and connect your source to main-in.

Seems kind of silly to buy this integrated amp just to use as a power amp. Take a look at the Niles power amp reviewed here. It has the auto-on feature you desire and adequate performance.

 

[pjug]

The C275BEE power amp has signal sensing.

 

[EasyGuy]

No it does not have audio sense.

And yes, to bypass the preamp just remove the jumpers between pre-out and main-in and connect your source to main-in.

Seems kind of silly to buy this integrated amp just to use as a power amp. Take a look at the Niles power amp reviewed here. It has the auto-on feature you desire and adequate performance.

Thanks, I'm new at this and dont know what I'm doing LOL.

I bought the SMSL DAC recommended on this website and also bought a Niles 275, but then it has CAP issues so then I got Niles 245 and they have been working great. Using it with my JBL 530 as a desktop speakers.

Just saw this having low noise level want to try this with my Klipsch RP-280.

 

[EasyGuy]

The C275BEE power amp has signal sensing.

Thanks will look out for that, I wonder if the noise level is as good as this one.

 

[pjug]

Thanks will look out for that, I wonder if the noise level is as good as this one.

Measurements can be found here: http://www.soundstagenetwork.com/in...er&catid=97:amplifier-measurements&Itemid=154

 

[Eetu]

Thanks will look out for that, I wonder if the noise level is as good as this one.

Keep in mind this one can be found used for ~150€ while the C275BEE is ~1400€ new..

 

[pjug]

Keep in mind this one can be found used for ~150€ while the C275BEE is ~1400€ new..

Indeed. On the other hand the C275BEE has a lot more power. But I agree that the price is high. Too bad that the C275BEE is the only Class AB power amplifier in the NAD lineup now.
My opinion is that other companies offer better value than the C275BEE, e.g Outlaw M2200 and Monoprice Monolith 2-chan.