Polyester film cap at the power amp input?

elnaldo · Apr 19, 2015

Hello. I have here a Pioneer SX-850 (it came to me after the "authorized tech service" charged $250 to the owner to do "NOTHING", and the unit keeps failing)

There are 2 coupling caps at the power amp input, directly in the signal path, 2.2uF and 1uF.

I can easily fit polyester film caps in there, plastic boxes like this:

they come in 63V, up to 3.3uF.

But they are not "polypropylene" film. Any problem with that? I've used this caps many times to replace small electrolytics.

avionic · Apr 19, 2015

I don't see why not. If it sounds bad you can always try something else.

jheu02 · Apr 19, 2015

If you can tell the difference vs polypropylene you have ears better than 95% of the planet I'd guess. But try it...

wlhd1610 · Apr 19, 2015

jheu02 said:
If you can tell the difference vs polypropylene you have ears better than 95% of the planet I'd guess. But try it...

Yeah,but you're forgetting that five percent are all here on AK.

elnaldo · Apr 19, 2015

I could stay with electrolytics too...

The thing is: once assembled, I'll not disassemble the board again to compare. There are just 4 caps in each channel, so I'll do it once, and assemble everything. I'm replacing the differential pair transistors (noisy), and do this recap.

jheu02 · Apr 19, 2015

Go with film vs 'lytic if you can fit it. Polypro MAY be better than Polyester, but either is better than "lytic.

bare · Apr 19, 2015

Input caps Can be significant. Those Blue plastic ones are 25 centers. Better (hopefully) than the 5 cent electros currently fitted
Adequate ..but imo a waste of effort as an upgrade.
Suggest a pair of Daytons Or Solen Film 'n foils (Blow the couple of Bux each

Or don't bother.

elnaldo · Apr 19, 2015

I think I understand.

I can't fit large caps there, and I can't easily get them. I'll stay with this polyester film caps, that I already have at hand...

ZOOM · Apr 22, 2015

If you put a big polypropylene capacitor there, you ruin the amp. Its sheer size will kill any potential better specification of the dielectric and may make the amp unstable, or have it pick up noise. Anyone claiming this to be an upgrade has zero knowledge in the field and should be brushed off entirely. There are too many ignorant loudmouths on the Internet, it is quite destructive.

mrdbdigital · Apr 22, 2015

ZOOM said:
There are too many ignorant loudmouths on the Internet, it is quite destructive.

Quite.

Dave :music:

ConradH · Apr 22, 2015

ZOOM said:
If you put a big polypropylene capacitor there, you ruin the amp. Its sheer size will kill any potential better specification of the dielectric and may make the amp unstable, or have it pick up noise. Anyone claiming this to be an upgrade has zero knowledge in the field and should be brushed off entirely. There are too many ignorant loudmouths on the Internet, it is quite destructive.

A bit direct, but often true. It always bugs me when people try to shoehorn physically unsuitable parts where they don't fit, and get large stray capacitance to ground or other parts of the circuit. I'm a big believer in the measured superiority of polypropylene over polyester (Mylar), but keep in mind that many highly regarded preamps (like ARC) have been full of nothing but polyester, and they do just fine. IMO, the worst film cap is still better than the best electrolytic.

elnaldo · Apr 22, 2015

I've read about large caps can pick some hum.

This the job done... They are larger than the 'litycs, but not so big... (replaced that 33uF cap after the pict)

nerdorama · Apr 22, 2015

elnaldo said:
Hello. I have here a Pioneer SX-850 (it came to me after the "authorized tech service" charged $250 to the owner to do "NOTHING", and the unit keeps failing)

There are 2 coupling caps at the power amp input, directly in the signal path, 2.2uF and 1uF.

I can easily fit polyester film caps in there, plastic boxes like this:

they come in 63V, up to 3.3uF.

But they are not "polypropylene" film. Any problem with that? I've used this caps many times to replace small electrolytics.

I assume you realize that the 22nF and 10nF in your picture are not 2.2uF and 1uF?

gslikker · Apr 22, 2015

the Sanyo ones you replaced are tantalums, we had some discussion about them on this forum. There also exist white Elna's which are probably the same. You probably did see at the bottom they are molded, looking different from normal electrolytic caps. Their weight is also more than aluminium ones.

The film ones you did put in will do fine, of course.

elnaldo · Apr 22, 2015

I assume you realize that the 22nF and 10nF in your picture are not 2.2uF and 1uF?

:yes: yes, the pict is from the vendor's web site, just to show the spacing.

I've used 1 and 2.2uF / 63V

I didn't know those Sanyo were tantalums !!! I'll take a look tonight!!

But for sure, the 2.2 measures 4.3uF in my multimeter, and the 1uF measures 1.4

avionic · Apr 22, 2015

ZOOM said:
If you put a big polypropylene capacitor there, you ruin the amp. Its sheer size will kill any potential better specification of the dielectric and may make the amp unstable, or have it pick up noise. Anyone claiming this to be an upgrade has zero knowledge in the field and should be brushed off entirely. There are too many ignorant loudmouths on the Internet, it is quite destructive.

Do not feed the bare trolls..

jheu02 · Apr 22, 2015

I'm pretty sure those light blue Sanyo's are "solid" aluminum electrolytic, NOT Tantalum. All the Tant's I've seen look somewhat like eggs.

gslikker · Apr 23, 2015

I did read this too, forum member ConradH found this info somewhere. Anyway I can not find any data on solid aluminium electrolitycs so that is why I assumed tantalum anyway (also because of the weight).
btw as other caps, tantalums come in different styles, here is a funny 100 µF 35V one I have salvaged

jheu02 · Apr 23, 2015

check Post #11 here

elnaldo · Apr 23, 2015

Reding a bit, it seems they are solid aluminum electrolytics.

They have a lifespan too, like 5000hs a modern one, so they age as other electrolytic caps, (even if the word "solid" made me think they don't)

Polyester film cap at the power amp input?

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