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Help with smoothing capacitor choice
Help with smoothing capacitor choice
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Old 29th November 2017, 09:02 PM   #1
thorondorwest is offline thorondorwest
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Default Help with smoothing capacitor choice

Hi,

This is my first forum post as I am a noob wrt electronics at a PCB level.

Anyway on to my question. I have two QSC RMX2450 power amps I am rehabbing for my HT, one for sub duty and the other for mains. I'm a bit stuck on which smoothing caps to choose, these amps have only 2 electrolytic caps in the signal path, one small value coupling cap I'm replacing with Nichicon UFG and four 12,000uf smoothing caps per channel.

The smoothing caps are bulged badly and in need of replacement. QSC specs a "high ripple" current cap and want $13 per cap (I need 16) and is a boutique part not available outside QSC supply chain.

Original cap is

ELNA LA5 series
12000uf
6.9A ripple current rated
.20 DF
0.028 ESR

QSC (expensive) replacement is
Nover LS series
12000uf
7.0A ripple current rated
.15 DF
0.028 ESR

On the market the closest I can locate is available from either Mouser or Digikey is:

EPCOS (TDK) B4123
12000uf
6.83A ripple current rated
.25 DF
0.027 ESR

I had to contact EPCOS for the ESR value and they verified that the cap is suitable for a smoothing cap in an audio amp.

Since Q is the inverse of DF am I risking distortion using a cap with a higher DF all other values being roughly equal? Could the low DF of pro amp caps be part of why the sound dry? I do realize higher DF=more heat but I don't think that's an issue in my application. I can get these EPCOS caps for 1/3 the cost of the Nover ones from QSC.

Should I go for it or pay 3x as much for a cap with .1 lower DF (higher Q) in a home theater application? Seems mostly an ultra low DF in pro amps to avoid heat loading in the abusive environments they operate in.

Am I missing anything? EPCOS B4123 is a pretty new cap- anyone have experience with how they sound?

Last edited by thorondorwest; 29th November 2017 at 09:07 PM.
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Old 29th November 2017, 09:22 PM   #2
indianajo is offline indianajo  United States
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I wouldn't worry about the "sound" of the mains filter caps. I don't know what you are calling "smoothing" caps, but 13000 uf sounds like rail caps to me. People that worry about the 3rd decimal place in the Harmonic Distortion spec, parallel the x000 uf rail filter caps with a 0.1 uf polyprophylene cap.
QSC is in the market where their products can run the power rating 24/7 in beach bars & such. In a sunny beach bar on some tropical island at full blast all the time, every little bit of heat not dissapated is a good idea. Leads to longer life. Makes more sales, having good reliability under stress.
In a home theater, you are not going to be running the power rating anywhere near 24 hours even at one showing. I'd buy the cheap ones.
OTOH, I get tired of replacing mains caps over and over again. My first amp I've done it four times. I'm still listening to music, and hope for four more decades. Hours service life matters to me a lot. You can buy up to 3000 hours in this class of snap in cap. Go for it. 1000 hour caps, that is planned obsolescence IMHO. And EPCOS is not real high on many guy's list of stellar electrolytic caps. Panasonic, Nichicon, Rubicon, Vishay that is the five star four vendors. I bought an EPCOS once, and I won't tell you where it was manufactured, but they had a baby food scandal a decade ago, and blew up a factory two days ago.
Best of luck.
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Last edited by indianajo; 29th November 2017 at 09:27 PM.
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Old 29th November 2017, 09:31 PM   #3
thorondorwest is offline thorondorwest
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Hi!

Thanks for the reply! These caps are >2000hrs per EPCOS. The Nover are rated 3000hr. I can't find a 3000hr cap without losing a full amp of ripple rating. I'll post a link to the service manual when I get home with a circuit schematic. I suspect you may be correct however the caps are in the signal path per the schematic which isn't what I'd expect (though a noob to be sure) for a PS cap. Could that be due to the amps being a flying rail design? Thanks for the education.

I'll ask Digikey where the caps are made but EPCOS is now part of TDK and has refreshed it's entire line since aqusition. Hoping it's Japan and not baby food exploding factory land. ��

Last edited by thorondorwest; 29th November 2017 at 09:38 PM.
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Old 29th November 2017, 09:47 PM   #4
phase is offline phase  United States
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I agree mostly about the sound and how it likely won’t make much difference.
I recall looking at one of the QSC amps and it didn’t have much room for “great” parts, so a higher quality part would require going to a lower uf capacity possibly.

Might have to keep digging.

I do like the b41550, b41505 for my projects, not available or too large for your amp though.
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Old 29th November 2017, 10:22 PM   #5
rayma is offline rayma  United States
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Quote:
Originally Posted by thorondorwest View Post
These caps are >2000hrs per EPCOS. The Nover are rated 3000hr.
I can't find a 3000hr cap without losing a full amp of ripple rating.
The voltage and temperature ratings are very important also.
Even the case form factor makes a difference in core heating and lifetime.
.
.

Last edited by rayma; 29th November 2017 at 10:26 PM.
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Old 29th November 2017, 11:12 PM   #6
thorondorwest is offline thorondorwest
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Default Finally at a real computer

So I called Digikey.

The country of origin for all of their capacitors regardless of brand is either China or Malaysia except for a single "audio grade" Nichicon which is Japan.

Original ELNA LA5 Cap Datasheet

LP5 PDF Datasheet - ELNA America Inc. - Datasheets360.com

EPCOS Cap (China)
B41231A8129M000 EPCOS (TDK) | Capacitors | DigiKey

UCC Cap (Malaysia)
ESMH630VSN123MA45T United Chemi-Con | Capacitors | DigiKey

Nichicon Cap (China)
LLS1J123MELC Nichicon | Capacitors | DigiKey

Nichcon "Audio Grade" Cap (Japan) (However ripple current rating is only 4.75A which is 2A+ shy of replacement.
LKS1J123MESC Nichicon | Capacitors | DigiKey

Kemet Cap (China)
https://www.digikey.com/products/en?...ds=399-6531-ND

Rubycon Cap (China but 3k hour rated)
https://www.digikey.com/products/en?...s=1189-3945-ND

After talking to Digikey almost every cap, Japanese branded or not, is now made in either China, Thailand, or Malaysia. They do not advertise the country of origin on the website because it changes constantly so you have to call and ask. According to their international sales rep this transition has occurred in the last 3-4 years and other than boutique products its all either China, Thailand, or Malaysia.

Brand probably has more to do with on site Japanese QC reps than where it is made any longer because 95% of their inventory is not from Japan. The entire UFG (FineGold) Nichicon line is made in Malaysia BTW, not Japan, at least not anymore.

OG caps are 63V 85c. I can fit anything that is 34x45-50mm in size with a 10mm snap in lead. I tried finding higher voltage values but couldn't find anything that fit these specs, will physically fit, and is inn a 12,000uf capacity. I don't want to go with the eBay route because I am concerned about counterfeits and Caps that have been stored beyond their shelf life as I have no ability to reform them.

The applications engineer I spoke with said that she recommends the EPCOS caps on a regular basis, has no record of a quality issue in their system, and considers the EPCOS/TDK parts to be on a par with Nichicon, Rubycon, Elna, and UCC.

One other option I have is CDE which is made in the good ol USA but does not provide an ESR value for the cap that would fit and isn't known (at least based on the internet "lore" for low ESR capacitors. However I do have a fried QSC PLX 3402 (blown IGBT) that uses CDE rail caps.

Here is a link to the circuit schematic for my amplifier. which shows these caps inline with the signal path:

http://schems.com/bmampscom/qsc/QSC_...ice_Manual.pdf

8910-0494-0 CE 63V 12000uF 20% RL 4 C120–C123
8910-0494-0 CE 63V 12000uF 20% RL 4 C220–C223

RMX2450 Circuit diagrams start on page 33, shaded gray line shows signal path, which clearly transits these caps (only shows it crossing one of them but they are wired in parallel so I am assuming that is why).

Thanks for willingness to help a NooB!

I am a bit stuck as I could order the OEM caps from QSC for the price of the Japanese Nichicon but can't really afford it at quantity 16. Tempted to give the EPCOS a shot but please flame mea if that is a bad idea. I do like the metal heat shield on the outside of the EPCOS.
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Old 30th November 2017, 12:14 AM   #7
thorondorwest is offline thorondorwest
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380LX123M063A052

CDE
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Old 30th November 2017, 12:25 AM   #8
thorondorwest is offline thorondorwest
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Looks like this is my best option:

380LX123M063A052

CDE made in the USA 3000hr rating DF .20, 7.0A ripple .024 ESR, 12000uf. $5.85 each from Mouser in quanties of 10 or more.
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Old 30th November 2017, 12:35 AM   #9
Henderson is offline Henderson
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The smoothing caps (after rectifiers) should be : LL (long Life), not too low ESR, better rated 105C° or more ! Have the same pitch between leads and feet in the PCB ! And have equal or better ripple than the former caps. I will not bypass them by a 0.1 MKP film cap !


Don't be worry about the country where they're made ! Be worry about the place where you buy them (so official seller for genuine part)


I don't like Nichicon for some reason but they are solid, CDE are ok ! Not sure Epcos Sikorel are a bad choice ! Anyway : they must feet on the pcb . Nichicon will "sound" more as an Elna (but some exception they tend to be smoother at ears than most (not sure it's a quality some like it)


you talked about a signal cap : if in serie (DC blocking), I don't know why you should swap it for a brand new one ! Take care if it's a bipolar to choose a bipolar as well!
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Old 30th November 2017, 12:37 AM   #10
indianajo is offline indianajo  United States
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I looked that the schematic, thanks for the link. The 12000 are just rail caps, plus something tricky to make the channels bridgeable, but still, just rail caps. Not a critical sound path position IMHO.
You have two plusses for the QSC sourced caps. They are rated 3000 hours instead of 2000. They are screened for **** by QSC instrumented incoming inspection department, which has the power to send them back no pay. That second is worth some coin. No distributor does that.
OTOH you can't afford the QSC caps now. Depends on how long you want this repair to last, IMHO. My main amp stays on 40+ hours a week, thus the 7 year life I was getting out of store front stock **** caps. Before internet service life data was a fantasy to hobbyests.
Enjoy your decision, its your hobby.
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