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Got a 10 uF tant in the signal path in a RIIA, between the first and second stages. The tant has a DC volt or two across it.
Would it be a sonic improvement to change it for a good 10 uF film cap instead?
Cheers, it's Friday
Edits: 09/06/07Follow Ups:
i'd use a film replacement. a single 10uF would be large and expensive. maybe parallel some smaller values (e.g. a couple of 4.7uF).
someone (george?) touched on failures of tantalum caps - when they fail, they short. a tantalum coupling cap that shorts would not put on as spectacular (!!) a show as a power rail tantalum cap that fails, but the rest of your circuitry might not like the DC that passes.
mlloyd1
The first comprehensive cap selection article; it still holds up well today. A true classic.
http://waltjung.org/PDFs/Picking_Capacitors_1.pdf
I prefer foil polypropylene caps; you can spend more, but this seems to be the sweet spot for me. In critical applications, tin foil/silver foil/polystyrene caps are better, but get very pricey. Some vapor deposited aluminum polyprops are good, some not. Construction details, especially lead termination, matter.
http://www.humblehomemadehifi.com/ for more current cap reviews.
Most caps require a breakin time of at least 40 hours before you can properly assess them. Much disputed, not well understood, but I find it so.
yes or a paper in oil .....imo
don't just remove it !
I do not like to use tants. A 10ufd film may be better. Even a good quality electrolytic should offer an improvement without the size problems from a film cap of this value.
A BG N series would be perfect, cheaper altternatives Pana FC, Rubycon Z series, or Silmic II. Any of the four should work as good or better than what is in there now.
George
Hi.
For signal path like interdstages, film is definitely beter than any polar caps. To replace a 10uF polar 'lytic coupling cap for DIYed SS phonostage, I ying-yang parallelled 5x2uF PE film caps. I had a hard time to get the space to house the builky parallel film caps.
But the emitter resistors bypass, I used 47uF tants for their very compact size.
So tell me how you find the soncis of tants.
c-J
I find tants work okay for decoupling applications. For coupling they lack clarity. That is just my opinion. I have never used them for coupling signal, my experiance has been in a feedback loop also. Replacing with a good quality electrolytic did add clarity and low level information.
I do not like film caps in this range of values either. A BG N series is better to my ears than a 10 ufd film. The FC, FM, and Rubycon Z series are all good coupling caps when more than a couple ufd is needed.
If the phono stage was mine, I would go with the BG NHX, 22 ufd, 6.3 volt model. These are extremely good if the voltage is within range.
Another downside to tants is early failure. They seem to not last as long as electros. Film usually are forever.
George
actually I found tantalums degrade clarity in decoupling applications as well e.g. opamp/dac PS decoupling. They seem to make the spectral balance less wide-band and more midrange-centric (though some people may prefer this).
Tants have problems when the AC signal voltage is greater than about 0.5V RMS
Actually polarized electrolytics do too although most of the spec. sheets specify 1.5 VAC or thereabouts.
A lot of mid-'70s gear brochures bragged about their use of tantulums in the signal path (implied). I'm a Lux gear collector and they used tants as output coupling caps and elsewhere.
I do use tants and MLCs for op amp decoupling with good results to my ears.
But I'd agree, most of the solid electrolytic caps still sound much better than the miniaturized low esr wound aluminum electrolytic kind. They aren't meant to be used in unbiased AC applications though, so shouldn't be used for coupling unless there is a guaranteed DC bias. But then again, most electrolytics really don't sound that good for coupling, especially without bias.
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