Nad C160 preventive recapping : good idea or not ?

[yoplaboum]

Hello gentlemen,
I own since a few weeks a NAD C160 preamp.
All is OK on it, no problem at all. But, because this preamp is 20 years old now (made in 1999-2001, I think), and because it's full of these very-loved JH capacitors , I wonder if it wouldn't be a sage idea to made a préventive replacement of these capacitors. I could read that these poor-quality caps could cause problems on gears younger than my preamp, so...
What's your opinion about it ? Is there a C160 owner who did that before, and if you agree with the utility to do these replacements, what's the best choice for new capacitor ? All Nichicon gold, all Elna Silmic II ? What's your advices ? And, a last question : do you think that, with better caps, there will be a general improvement on the sound quality ?
Thak you, and pacefull sunday !

 

[Douglas Blake]

Well, first let me explain that I'm kinda old school, been in electronics all my adult life.

Generally it is not a good idea to try fixing something that already works just fine. This is for multiple reasons, but the big one is that most unnecessary repairs end up causing even more necessary repairs. "If it ain't broke, don't fix it".

I've seen 30 and 40 year old gear that works just fine with all the factory parts... age is not a strong indicator.

Any sonic improvements from expensive "audiophile" capacitors will be very minimal, if even noticeable.

So my vote is that you should save your money until the amp genuinely needs repair.

 

[mbz]

I missed the talk on JH capacitors.

At 20years old and a preamp I wouldn't rush with a recap.
Certainly open it up and inspect caps for any physical abnormality
(leakage, bulging, shrunken sleeve...) and consider replacing those.
Give it a good listen, if it sounds ok then defer the recap.

I've recapped 20-30 amps mostly 1970's results have been dramatic in
some cases and "no significant improvement" in others. I don't like
the approach of using "all xxxx", need to identify the function of
the cap and select a replacement having the same attributes.

For something like the C160 I would go with
- Nichicon KW's for main filters, slightly increase uf and V
- Nichicon PW's for power supply maybe use Nichicon KZ after
voltage regulators
- Nichi EP for any bipolar in power supply
- Nichi ES for any bipolar in audio path
- Nichi KZ for audio path
- Nichi UKL for low noise/leakage in phono stage and early pre
Some prefer Wima MKS2 which I think can sound harsh, might
improve after a few(20-50?) hours
- Nichi KZ for local power rails
- Nichi PW for any non-audio path like protection circuit, rail
noise path to GND, display...

I was a long time user of Silmic II in the KZ positions above but
have switched caps in the last few months.

 

[indianajo]

I've seen 30 and 40 year old gear that works just fine with all the factory parts... age is not a strong indicator.

20 years on a preamp is not an extreme life. I'd leave it until it sounds bad. Special "audio" e-cap are a scam, IMHO. I buy the long service life industrial grade from Panasonic, Nichicon, Rubicon, Multicomp, occasionally Vishay. 10000 hours if I can get it, nothing less than 3000 hours in the large ones.
Since the entire consumer electronics industry moved out of the country, I've been trying to use entertainment gear made here.
NONE of it has lasted 30 years without fault.
I don't usually start on something until it shows a symptom. Loss of volume, bad sound, channel imbalance, too much highs or lows. Warped picture on televisions.
There were some Fender guitar amps made with electrolytic capacitors sealed with epoxy. David a instrument repairman from SC tells me those need no e-capacitors. Hammond B's had no e-caps or power amps so they do fine without e-caps. The power amp was in the Leslie that needed them every 10 years.
Everything else has needed them. When one goes I do them all, as replacing e-caps one at a time means your gear is broken all the time. In addition gear made before 1962 will have paper dielectric capacitors which can go off value if not brands sealed with wax. I've put as many as 199 e-capacitors in 1968 Hammond H organs.
Allen, an organ brand that the factory authorized repairman tells everybody on organforum needs no capacitors, a 1980 model went silent a Sunday in 2017. When I got there the 100 W amps were putting out 2 watts. 28 e-capacitors later they were operating at 100 W and I heard it play yesterday, 11/19. A 1990 Allen toasted a PTC resistor used as a fuse in the switcher DC supply. All new e-caps and a PTCR put that one back in service.
BTW some gear comes with e-caps with a service life of less than a year. A DTV converter from ***-Mart came with diagonal lines that went away after 20 minutes. A sure sign of dodgy e-caps from the factory.
Change caps 2 at a time and listen test in between. You'll find you make about 20% bad joints in the beginning, and putting them in backwards is not unheard of. Mark + on the board before removal. If you make a mistake that can be heard, you'll know right where to look if you didn't do too many parts at once.

 

[Mooly]

Well, first let me explain that I'm kinda old school, been in electronics all my adult life.

Same for me.

Generally it is not a good idea to try fixing something that already works just fine. This is for multiple reasons, but the big one is that most unnecessary repairs end up causing even more necessary repairs. "If it ain't broke, don't fix it".

We do see numerous examples of this on the forum unfortunately. You need to be methodical, have all the replacement parts to hand having first selected suitable replacements in terms of performance, life expectancy, and physical size.

I've seen 30 and 40 year old gear that works just fine with all the factory parts... age is not a strong indicator.

I have a Sony TCK5 cassette deck and ST515L tuner, both 100% original electrically. Some (including modern) equipment uses parts that are less than stellar in quality. A good visual inspection and look at the manufacturer of said parts will often be a decider in what to do.

Any sonic improvements from expensive "audiophile" capacitors will be very minimal, if even noticeable

Minimal... as much as that

So my vote is that you should save your money until the amp genuinely needs repair.

Yes and no. I'd say it depends on your goals and abilities. A recap done properly and carefully is an interesting exercise... just be aware of your limitations and proceed accordingly. You can also look over areas that run hot, reflow joints and perhaps even replace obviously distressed looking parts that have been cooked over the years such as Zeners in regulators and undercooled transistors, typically used in series regulators. If it were a power amp I would be looking at hot running VAS stages and probably replacing the semiconductors as a matter of course in those locations as many 2SB/2SD devices often used have some weird age/heat related intermittent failure modes.

 

[yoplaboum]

So, thank you very much for all these opinions. I think I will just have a carefull look on the capacitors, on heat marks... I understand that a preamp is less stressed than a power amplifier. I was wondering about recap it because the net is full of NAD products, younger than my preamp, who had problems because of these JH caps, they haven't a good reputation, about quality or reliability... It's the best option, you're right, to leave this preamp as it is since it works fine.
And thank you mbz for these details about all the Nichicon audio types. Except for the bipolar, I didn't know what to use for what part of an amplifier. It's very usefull !!

 

[Douglas Blake]

So, thank you very much for all these opinions. I think I will just have a carefull look on the capacitors, on heat marks... I understand that a preamp is less stressed than a power amplifier. I was wondering about recap it because the net is full of NAD products, younger than my preamp, who had problems because of these JH caps, they haven't a good reputation, about quality or reliability... It's the best option, you're right, to leave this preamp as it is since it works fine.
And thank you mbz for these details about all the Nichicon audio types. Except for the bipolar, I didn't know what to use for what part of an amplifier. It's very usefull !!

No harm with a good visual inspection and cleaning.

I bring in chip amps from China and often I will change the bulk supply caps because I can tell, just by looking, they are not going to last. But, other than obvious quality issues, I tend to avoid unnecessary teardowns.