advertisement


Vishay BC128 capacitors

Luca

Luca

pfm Member
Hi everybody,
the BC128 capacitors are no longer manufactured. What alternatives do you suggest to use for C11 on Avondale NCC200 and NCC220 PCB?
Thanks in advance for your reply,
Luca
 
Last edited:
Thank you Alan and Glenn.
Out of curiosity, aren't tantalums good as replacement of these solid electrolytics?
 
An other question: do the solid electrolytics last more years than standard electrolytics when kept in stock or NOS?
 
Luca said:
Thank you Alan and Glenn.
Out of curiosity, aren't tantalums good as replacement of these solid electrolytics?
Click to expand...

Yes they are but they will give you a different sound signature if used in the signal path. That might be very subtle though.
 
The solid electrolyte in tantalum capacitors is traditionally manganese dioxide, actually a semi-conductor. It ain't going anywhere fast. Stored VERY damp, they will pick up moisture and might leak a bit - if in doubt put a very few volts across them and they will repair (NOT reform) - I would say measure the leakage current, but that is going to be so low...……….. unless you have a genuine dud.
Th other option is solid polymer electrolyte, although I'm unsure how common they are. There was a huge push to make them when I was working in tantalum R&D because they are potentially far cheaper to make. The same logic applies as with manganese dioxide.
They both have an almost indefinite shelf-life otherwise.

I suppose VERY long term they would go open circuit due to oxidation of the silver in the silver inks used as part of the connection between the cathode and the lead/lead-frame.
 
Gervais Cote said:
Yes they are but they will give you a different sound signature if used in the signal path. That might be very subtle though.
Click to expand...

Please can you explain me how might be that subtle different sound signature? Anyone told me that the tantalum cap gives a edgy high frequency tone. Is it right?
 
EHEHEHE! I've just found a seller of ultra-NOS BC128 caps all very seasoned because they were made in the 70s and 80s. :)
Are these the bargains on ebay?
 
I haven't looked at precisely what they are but seriously - just to avoid the chance in a very high number, put a volt across them and slowly, over an hour or so, wind it up to operating volts, then hold for an hour. Solder them across two tracks of strip board and do all at once.

Want to be ultra cautious - measure the current - it should be unmeasurable with a normal meter.
 
Luca said:
Please can you explain me how might be that subtle different sound signature? Anyone told me that the tantalum cap gives a edgy high frequency tone. Is it right?
Click to expand...

Yes, according to the tests I did, the tantalum gives a rough treble, generous bass and lack of soundstage. When I replaced these with Wima polyester, the treble became softer to my ears. The sweet spot where they have the biggest influence is at the decoupling position or just at the input in a preamp.
 
Tantalum caps are poor for audio...

Polymer caps such as Oscon show amazing low ESR on my meter. In a different league to normal electrolytics in fact and a 470uF 16V Sanyo Oscon easily beats huge 22000uF screw terminal computer grade electrolytics the size of a tin of beer! Unfortunately leakage currents are very high which limits their usability.
 
Arkless Electronics said:
Tantalum caps are poor for audio...

Polymer caps such as Oscon show amazing low ESR on my meter. In a different league to normal electrolytics in fact and a 470uF 16V Sanyo Oscon easily beats huge 22000uF screw terminal computer grade electrolytics the size of a tin of beer! Unfortunately leakage currents are very high which limits their usability.
Click to expand...

Hi Jez,
So, apart from the Polymer caps, which alternative to BC128 would you choose?
 
Luca said:
Hi Jez,
So, apart from the Polymer caps, which alternative would you choose?
Click to expand...

I don't consider capacitor sound to even matter beyond an Nth degree level in power amps. Ideally use polypropylene but it will be huge to get the uF's.

I'm not suggesting using polymer for this application.
 
You must log in or register to reply here.


advertisement


Back
Top