I'm replacing some old (1980-ish) 1uF 160V lytics in the bias supply of a Stax headphone adaptor. The original 40-YO Panasonics ESR measures about 2 Ohms. Last month I ordered some Nichicon UPJ 1uF 200V:
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Capacitance at 1kHz was fine but ESR was 7-8 Ohms in all of them. Nichicon does not give an ESR spec for their 200V and up units in this series, but the date code on the caps is 1248 - 48th week of 2012! No wonder ESR is high, methought - they've been sitting in DK's warehouse for 9 years. I called them, they apologized, and issued a refund.
They also connected me to one of their techs, who looked at all of their 1uF offerings in that voltage range, and suggested this Illinois 1uF 350V one, which they had just received a shipment of:
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Illinois does not spec ESR on these either, but they're new so they must be good, eh? Well these were even worse, with ESR's of 12-17 Ohms!
Is this the norm for HV 'lytics?
I'm thinking of punting and using 1uF 250V films with 100mOhm R added to damp the HF resonance.
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Capacitance at 1kHz was fine but ESR was 7-8 Ohms in all of them. Nichicon does not give an ESR spec for their 200V and up units in this series, but the date code on the caps is 1248 - 48th week of 2012! No wonder ESR is high, methought - they've been sitting in DK's warehouse for 9 years. I called them, they apologized, and issued a refund.
They also connected me to one of their techs, who looked at all of their 1uF offerings in that voltage range, and suggested this Illinois 1uF 350V one, which they had just received a shipment of:
Blocked
Illinois does not spec ESR on these either, but they're new so they must be good, eh? Well these were even worse, with ESR's of 12-17 Ohms!
Is this the norm for HV 'lytics?
I'm thinking of punting and using 1uF 250V films with 100mOhm R added to damp the HF resonance.
Thanks for your input guys. I'll look through my parts boxes and see if I have something here that will fit on the pcb. These are post-zener smoothers so I don't expect them to impact sound quality. My main concern was whether or not to add the damping R, it's a long inductive path from there to the headphones.
Actually, they do.
In my ESL57, I tried the WIMA MKP 10 0.01uF/3KV, then the Chinese CBB81 0.022uF/2KV, both polyprop, and they sound noticeably different. Whether it's due to the value, the difference in the film or the manufacturing process, I don't know.
> 1uF 160V ...ESR ...2 Ohms. ....Nichicon UPJ 1uF 200V...ESR was 7-8...
1uFd at 120Hz (US power ripple, or below a 'stat's response range) is like 1,300 Ohms reactance. And the whole 'stat is 100k or more. What is another 2, or 8, ohms on top? If it mattered, they would have used 5 or 10 uFd.
1uFd at 120Hz (US power ripple, or below a 'stat's response range) is like 1,300 Ohms reactance. And the whole 'stat is 100k or more. What is another 2, or 8, ohms on top? If it mattered, they would have used 5 or 10 uFd.
You have a point here as proved by JLH way back in the 80,s , while being criticized for his views on the tonal differences between capacitors of the same capacity and working voltage in relation to polypropylene but in much different price bracket.
He did what I would do ---open several up and checked the type of plastic used .
It came as no surprise that the cheap ones used packaging polypropylene , so yes Zung you only get what you pay for .
As the capacitors required in this thread are only used for polarisation and not in the signal path then that's a different story and metallised will do --saves me from posting my reasons as to the quality of reproduction in metallised and FF -flim foil.
Exactly what I'm talking about, except it's polarization for the much larger "panels" in the ESL57, within a voltage multiplier to supply 1.5KV for the mid-hi panel and 6KV for the bass panels.
The WIMA are $0.75/ea, and the CBB81 are $0.20/ea, so there's a difference, but no where near "audiophile grade" difference. The funny thing is, I'm not sure which one I prefer: the WIMA seem more balanced, and the CBB have a slight emphasis in the upper mid, but it's the latter I choose to keep for the extra punch.
I do have some Leclanché film/foil caps, but they're too big for the available space: with 6KV on hand, there's a real need to leave plenty of room around them.
Well I have to say, they actually did. To my surprise, the low-freq end of the spectrum cleaned up nicely with the films.
Stock polarization voltage on this adapter is 160V. I'm going to change the back-to-back zeners and bump it up to 200.
I'd check:
* DC voltage
* AC voltage swing vs maximum supported AC swing.
* ESR.
If you look at some the DC link caps, they give great ESR - an 80uF WIMA MPK4 gives 0.003ohm! Great for SMPS.. but then look at the AC vs DC ratings.. you'll see that you're likely to need quite a high rating.. iie the next step up DC rating is needed to support the required AC Vpeak-to-peak requirement.
So a 200-320V B+ with ±4V.. then that's not too bad but try the same trick with ±100Vac peaks for driving large tubes.. then you may start causing the cap problems.
IIRC the 420Vdc DC Link has a 200Vpp AC rating. If you look at the 630Vdc rating it has a 400Vpp AC rating.
Also look at the derating vs temperature. Using a single cap may cause the temps to rise further vs simply adding two in parallel (smaller capacitance) to reduce the ESR and keep within the derating. Issue then is ensuring an even balance...