NAD 2200 Vintage Amplifier Review

[restorer-john]

In fact, here is an example where the elusive crossover distortion seems to be showing itself a little bit.

That is at 71W@8R and we don't know the scale or multiplication. No conclusions can be drawn.

 

[pjug]

That is at 71W@8R and we don't know the scale or multiplication. No conclusions can be drawn.

Yes that always bothers me that JA does not show the scale. Still, you don't agree with JA that this is crossover distortion showing?

 

[pjug]

Hm i have a NAD C370 that runs now for more than 17 years no problems what so ever. I think the amount of NAD's produced like the C370 in the ten or hunderd of thousends can obtain some problematic amplifiers in comparison to amplifiers brands that are producec a few thousend or less i guess.

The C370 can also be seen as an example of NAD not being reliable. It has the protection circuit problem (defective design). I had to repair mine. Luckily it is easy DIY repair thanks to instructions available on the internet.

 

[restorer-john]

Yes that always bothers me that JA does not show the scale.

Just put into perspective what the gain is and the scale, that's all they need to do. Say "distortion residual at -60dB (x1000), same scale range (in V/Div) as fundamental as indicated" or something equivalent, otherwise, it's just a pretty meaningless picture.

 

[pjug]

Nope. Sunfire Stereo. I believe Emotiva currently sells Class H amps in their XPA line.

I was just kind of joking about this and noting the AHB2 model designation. The point being that nobody needs to be bothered by calling these kinds of amplifiers Class AB. I think it is proper to say Class G and Class H are subsets of Class AB. Benchmark refers to the AHB2 as a Class AB amplifier in their own literature.

 

[Snarfie]

The C370 can also be seen as an example of NAD not being reliable. It has the protection circuit problem (defective design). I had to repair mine. Luckily it is easy DIY repair thanks to instructions available on the internet.

I know of this problem and the quite simple solution by replacing some capacitors but the discussions i found on this issue (some years ago) with the protection circuit an other issues can be probably related to the vast amount of NAD C370 that are produced at the time with probably a series(s) of bad specs of capacitors from the start. Because this circuit problem did already occur after a few years after introduction. To check all ic's, capacitors etc. etc. for all amp's is just not feasible from a price point of view i guess.
So probably after 17 years + i still don't have this problem because my capacitors are still with in the specs i guess. You have to make an comparison how much there where produced and how many have this problem/issue before you can speak of a general C370 issue imo.

Lots of problems i found regarding NAD or other brands over the years are bad sold-rings in general like binding post that wear out overtime. My old JK acoustics integrated class A amp after 15 years all binding post where bad an has to be re-soldered the binding post of my C370 are still ok no bad contacts or channels that are working after 20 minutes. What i do regular at least once every 2 years is open the box clean it with high pressure air an if necessary use some contact spray mostly the tone an balance control ha ha that i don't use.

There are so many circumstances that a piece of gear can go wrong before you can speak in general about reliable issues imo.

I'm curious do you still have the C370. If your C370 will be broken beyond repair which amp would you buy. For now i still love it sound tight an clean.

 

[pjug]

I'm curious do you still have the C370. If your C370 will be broken beyond repair which amp would you buy. For now i still love it sound tight an clean.

I still use the C370. But in the last couple years I bought Outlaw M2200 pair (because of review on this site) and also a Sonos Amp. So pretty much complete opposites in terms of old school simplicity vs modern integrated feature conveniences!

 

[Snarfie]

I still use the C370. But in the last couple years I bought Outlaw M2200 pair (because of review on this site) and also a Sonos Amp. So pretty much complete opposites in terms of old school simplicity vs modern integrated feature conveniences!

I did hear some Hypex amp that also tested here more or less same sort of thight sound as the C370 produces. Coudn't hear much difference thats why i'm curious about a ASR test. If mine is beyond repair i probably will go for an couple of Hypex amp's esspecialy because these Class D build amp's are relative cheap, powerful, simple/elegant not much can go wrong over the coming years i guess.

 

[pjug]

I did hear some Hypex amp that also tested here more or less same sort of thight sound as the C370 produces. Coudn't hear much difference thats why i'm curious about a ASR test. If mine is beyond repair i probably will go for an couple of Hypex amp's esspecialy because these Class D build amp's are relative cheap, powerful, simple/elegant not much can go wrong over the coming years i guess.

Also NAD still sells the C275BEE, which pretty much measures up to the NAD 2200 in this review. It wouldn't be a bad choice for replacing the C370 if you wanted to stay with NAD Class AB: https://www.soundstagenetwork.com/i...bee-stereo-mono-amplifier&catid=97&Itemid=154
But a pair of Outlaw monos cost me half what the C275BEE go for.

 

[Snarfie]

Also NAD still sells the C275BEE, which pretty much measures up to the NAD 2200 in this review. It wouldn't be a bad choice for replacing the C370 if you wanted to stay with NAD Class AB: https://www.soundstagenetwork.com/i...bee-stereo-mono-amplifier&catid=97&Itemid=154
But a pair of Outlaw monos cost me half what the C275BEE go for.

Besides the sound quality what i like about the C370 it is relative easy to replace ic's/parts on the mainbord if neccecary. It is easy to open the bottom board. Suppose i will get the protection circuits problem i Will repair that my self at the same time now the C370 is dismanteld other Possible upcoming problems could be adressed. I guess with around 150,- euro's for spare parts you can come a long way. It will function for many years more as the tested NAD 2200 does i guess.

 

[martin900]

C370 has many, many more problems, having a one that still runs could be considered 'luck' or it has been recapped and the solder job re-done before. The early series had exploding power supply capacitors (!!) because of flawed design, the solder job was insufficient which caused the caps to partially break loose and the ripple made them go pop over time.
I've also seen bodge wires from the factory in mine, they even advised to place a jumper wire instead of using the PCB tracks for ground there...

The class-A modules contain tiny capacitors, all of which were completely burn out in mine, solder joints so crusty you could pull out the components from the PCB. I've cut off all the top covers on mine to save the new capacitors.
I've marked the spots that need urgent recap in the C370, there are also a few caps surrounded by the rectangle heatsink of the drivers, these get roasted too.
Overall the C372 is a much better designed amplifier that adresses most of c370's flaws.

 

[pjug]

Also my C370 has pretty loud lamination hum from the transformer. I tried pressure-potting with epoxy and also a DC blocker; didn't help.

Oh, and now I remember I had to re-do solder joints on one of the power amplifier cards.

 

[Snarfie]

C370 has many, many more problems, having a one that still runs could be considered 'luck' or it has been recapped and the solder job re-done before. The early series had exploding power supply capacitors (!!) because of flawed design, the solder job was insufficient which caused the caps to partially break loose and the ripple made them go pop over time.
I've also seen bodge wires from the factory in mine, they even advised to place a jumper wire instead of using the PCB tracks for ground there...

The class-A modules contain tiny capacitors, all of which were completely burn out in mine, solder joints so crusty you could pull out the components from the PCB. I've cut off all the top covers on mine to save the new capacitors.
I've marked the spots that need urgent recap in the C370, there are also a few caps surrounded by the rectangle heatsink of the drivers, these get roasted too.
Overall the C372 is a much better designed amplifier that adresses most of c370's flaws.

I guess the majority that runs a C370, 2200 or any other vintage NAD flawlessly for more than 17 years are probably the majority i guess because they have nothing to complain about you don't hear them. The C370 i bought was used the person i bought it from assurd me that he bought it original he still had the receipt an the C370 was still 100% original no complaints all these years. To be sure i will make some inside pictures see if for instance if the protection circuit is modified. But it is good to know which problems could occure as you describe above.

 

[Wes]

Just as the engineers here expected. Crossover distortion is a non issue in properly biased class A/B power amps.

engineers elsewhere have worked hard to reduce Crossover distortion

I would also not draw the conclusion that this amp has reduced Crossover distortion to a non issue without an experimental test.

 

[LTig]

engineers elsewhere have worked hard to reduce Crossover distortion

I would also not draw the conclusion that this amp has reduced Crossover distortion to a non issue without an experimental test.

What kind of test do you propose?

 

[Wes]

Listening tests - you need to bridge the gap between a suite of measurements and actual ability of humans to differentiate products

 

[Snarfie]

C370 has many, many more problems, having a one that still runs could be considered 'luck' or it has been recapped and the solder job re-done before. The early series had exploding power supply capacitors (!!) because of flawed design, the solder job was insufficient which caused the caps to partially break loose and the ripple made them go pop over time.
I've also seen bodge wires from the factory in mine, they even advised to place a jumper wire instead of using the PCB tracks for ground there...

The class-A modules contain tiny capacitors, all of which were completely burn out in mine, solder joints so crusty you could pull out the components from the PCB. I've cut off all the top covers on mine to save the new capacitors.
I've marked the spots that need urgent recap in the C370, there are also a few caps surrounded by the rectangle heatsink of the drivers, these get roasted too.
Overall the C372 is a much better designed amplifier that adresses most of c370's flaws.

I have looked at the solder joints on the protection circuit i could not make a picture it is to narrow for my mobile phone however the solder joint looks what i could see original. Some pictures including some temp measurments if that helps. It looks like the zener diod does not run hot just 43,4 degrees C. In cold conditions protection circuit clicks in 4 or 5 seconds on. The C370 was on for 2 days. For about 7 minutes amp was shutdown to open top taking pictures. Than started it again waited for 20 minutes to do temp measurments.

C370 on for several hours laserpoint on the diod an other items
Diod

 

[DualTriode]

just purchased a couple of replacement relays.
any secrets to removing the old ones?
clear relay on the left is the new one.

 

[restorer-john]

any secrets to removing the old ones?

Never solder or desolder without pants.

 

[Doodski]

just purchased a couple of replacement relays.
any secrets to removing the old ones?
clear relay on the left is the new one.View attachment 68459

Use a solder sucker or solder braid wick to absorb the solder on the PCB.