NAD C375 integrated amplifier, better sound changing some comp..?

[Hangaard]

Hi Everyone, I have got a NAD C375 integrated amplifier, can i get the sound quality up a little bit by changing some components in it?
What would you suggest and with which?
attaches the service manual link
NAD C375BEE - Manual - Stereo Integrated Amplifier - HiFi Engine

 

[Mark Tillotson]

How old? If its old enough replacing capacitors may be a wise move, otherwise I'd suggest checking offset and bias, preventative cleaning of pots and switches, and careful vacuuming up any accumulated dust, and good visual inspection.



If you have the ability testing it meets the published specifications might be a first step towards any improvements/changes.

 

[Hangaard]

Hi Mark, do not know the exact age it was made from 2009-2015 but it is newer than 2011.
it is newly adjusted and quite clean, has even thought if a little could be obtained by changing the capacitor, however, have not been able to find the 22000uf 100V as the dimensions are 50 * 80mm and max length is 95mm or there is no space.
What if there could be components directly in the signal path?

 

[mbz]

any amp manufactured in 2011 will NOT need a recap. Sounds like you are wanting a tweak to improve the sound quality. As above, maybe run some tests against the specs, square wave tests may help. What aspect of the sound are you wanting improved. Might be best to buy a more suitable amp.

 

[Hangaard]

Hi MBC, I like to tweak my Hi-Fi
I am not educated in the field but can actually figure out how to solder, so there are also limits to what I have of measuring equipment besides a voltmeter.
I had hoped that especially the treble could get a little better, it seemed to be a little sharp, but yes I like to tweak my equipment.
Also why I ask in here as I am not strong in what components I could replace with advantage for some better.

 

[paulys55]

What does the rest of your audio chain consist of? I have this same int amp so was just curious

 

[sgrossklass]

Modern-day NADs are occasionally let down by parts quality, but tend to be some of the best-measuring products as-is. Trying to improve on the work of a seasoned pro like BEE (who has been doing this since the 1980s at least) seems like an exercise in futility.

I'd suggest finding a more appreciative vintage candidate if you've got a bad case of "tweaking fever". Or improving upon speaker placement and room acoustics. That's where you've got some real leverage. Amplifiers tend to be good enough either way.

 

[Hangaard]

Hi paulys55, It plays on B&W 685 in my kitchen, but over time I have had some different equipment and currently compares it to a Parasound HCA-2200Mk2 and has just had a Parasound Hint which on paper performance is comparable to NAD but NAD cannot keep up with this, but of course there is also some difference in the price.
But sometimes small modifications can do a bit for the quality of the sound, and here are a lot of talented people in here so hope for some small gold grains

 

[Hangaard]

Hi sgrossklass, you are probably right but now I got this NAD quite cheap so it would be nice if i could raise the sound quality a bit, but it may be a wrong choice in amplifier for the purpose.

 

[Douglas Blake]

Hi Everyone, I have got a NAD C375 integrated amplifier, can i get the sound quality up a little bit by changing some components in it?
What would you suggest and with which?
attaches the service manual link
NAD C375BEE - Manual - Stereo Integrated Amplifier - HiFi Engine

There are design flaws and manufacturing shortcuts that sometimes require update parts but that's pretty rare nowaday. Most of the time, changing parts that aren't broken does nothing to improve an amplifier ... or anything else for that matter.

The notion that you can tune your system with wire or solder is pretty silly if you stop and think about it.

 

[Max Martin]

There is a 10uf electrolytic (301/401) in the signalpath, and a few ceramic caps that could be replaced to Wima FKP for example. I would recommed to replace all caps. My 2200uf/ 50V was leaking.
Like sgrossklass said they're totally let doen by bad parts and mostly here its the caps.. JH (jinghai?) and the are BAD.

Also replace the 4x2.2K (3W) res to 5w, they run insanely hot! Also down by the 18v reg there is 2x200R that could be 3w instead of 1W.

Have you checked all voltages? 18, 64 and 68 if i remember right

Anyway this amp was manufactured from 2003 to 2008. The C275 came after that.

Hangaard; You have PM

 

[Max Martin]

Btw, i think this amps sounds far from sharp, with my Be tweeters it is very sweet and warm treble.

 

[Max Martin]

Well, see now this was about c375, not c372/272. Sorry

 

[esparto]

C375BEE R195 overheating ?

There is a 10uf electrolytic (301/401) in the signalpath, and a few ceramic caps that could be replaced to Wima FKP for example. I would recommed to replace all caps. My 2200uf/ 50V was leaking.
Like sgrossklass said they're totally let doen by bad parts and mostly here its the caps.. JH (jinghai?) and the are BAD.

Also replace the 4x2.2K (3W) res to 5w, they run insanely hot! Also down by the 18v reg there is 2x200R that could be 3w instead of 1W.

Have you checked all voltages? 18, 64 and 68 if i remember right

Anyway this amp was manufactured from 2003 to 2008. The C275 came after that.

Thanks for your analysis.

I have an issue with my C375BEE on the left poweramp board, it came up when I noticed a slight background noise by just turning the amp ON and waiting.

I investigated and made tests ... as soon as I blow on R195/100Ω, 1/6W, 5%, with a thin long plastic tube, the noise stops, but then comes up again, etc.

Visually this resistor doesn't seem affected though.

On the contrary as you mention other resistors can be hot and visually brown, smoked, ... R132/2K2Ω, 1/6W, 5% aspects changed and even reveals its metal, or perhaps the metal fil,m has melt.

I'll replace all these as well as capacitors like C126/100nF, ±5%, 63V by better ones.

Best Regards.