Tantalum CKs?

[wizard333]

Tantalum cathode bypass caps........Any reason to or not to use em? Right off the top of my head, seems the adantage would be they shouldn't wear out like electrolytics. Disadvantage would be cose (maybe). Anything else?

What voltages would be "safe" in place of the std. 22uf/25v scenario? Seems those amps never see much more than 3v at the cathode. A 22uf/25v Tantalum is over $4 a pop .....kinda pricy. Price goes way down at 16v or 10v.......safe and reliable or don't go there?

[Enzo]

SOme guys like them. Me, I wouldn;t touch them.

They are totally intolerant of reverse voltage and don't like overvoltage. yes, most cathodes sit there at 2v or less, but that doesn;t guarantee a tube will never deliver a voltage blow to its little tantalum chin.

And wear out? I imagine in another 20 years, you might be thinking about replacing them if they were lytics. And 22/25v axial Nichicons are selling for 25 cents.

Try this. Get out an amp chassis, scope the cathodes of a couple stages with realistic guitar signal input to the amp. But remove the cathode bypass caps on those stages. Get an idea what signal levels there are. Obviously the first stage will look different from later ones.

Of course all that is just my opinion. others may well reasonably disagree.

[daz]

I tried them. At first they seemed like they were good by giving greater clarity. after a short time it became apparent they were actually not good. I started hearing a sterility that was extremely apparent when i went back to electros and heard how much better it was with those. I'd say don't bother, but then who knows....there are those who use them.

[hasserl]

I used to use them a lot, and sold a ton of them in kits. But in a couple of circumstances, after I completed mods on an amp and fired it up I had a lot of noise that I traced down to the tantalum bypass caps. After the 2nd instance I stopped using them, or including them in kits. Back to electrolytics for me.

[tedmich]

Tantalum cathode bypass caps........Any reason to or not to use em? Right off the top of my head, seems the adantage would be they shouldn't wear out like electrolytics. Disadvantage would be cose (maybe). Anything else?

What voltages would be "safe" in place of the std. 22uf/25v scenario? Seems those amps never see much more than 3v at the cathode. A 22uf/25v Tantalum is over $4 a pop .....kinda pricy. Price goes way down at 16v or 10v.......safe and reliable or don't go there?

Mesa uses them a lot, and 10v should be fine (the newer Kemets with the conductive polymer cathodes don't explode like the older ones with manganese dioxide cathodes). Could try the newer niobium oxides or oscons too, and Merlin likes NP ELs I believe.

[wizard333]

Whats an NP EL?

[Albert Kreuzer]

Non-polarized electrolytic.

[wizard333]

Thought those were not available in sizes much bigger than 1uf?

[Enzo]

They are used in speaker crossovers, and can be large in value. Like 100uf or something.

[tedmich]

Some say you can make a non-polarized capacitor by putting two equal polarized electrolytics back-to-back: -[]++[]-

you of course get 1/2 their capacitance and equivalent voltage

I have not tried this, but it seems sound. For higher voltage applications some suggest parallel diodes or a central biasing voltage, see:
Sci.Electronics.Repair FAQ: Capacitor Testing, Safe Discharging and Other Related Information

[anson]

I'll share with you folks my experiences in tinkering around with different caps:

I tried 22u and 47u tantalum caps as preamp bypass caps, and like daz have thought them to be good at first but later felt that they weren't that great.

To my ears they did seem to be a bit clearer sounding at first, clearer than the polarized electrolytics i was using anyway. After playing for a while and analyzing the tone (with my ears) though they sounded a bit dry, grainy, and flat, to me. That being said, I think that they can be a legitimate tool in creating the tone of an amp. It just depends on what sound you're going for.

Polarized electrolytics have always seemed a bit sloppy and loose sounding, at least the larger sizes like 22u and 47u on my builds. I've changed to non-polarized electrolytics and they seem to have improved clarity in the bass frequencies. Non-polarized caps are now my favorites.

[wizard333]

Where are you sourcing the large value non-polarized electrolytics? And did you also lower the values you were using from 22uf to something else?

[tedmich]

Where are you sourcing the large value non-polarized electrolytics? And did you also lower the values you were using from 22uf to something else?

the hifi heads have a ton of NP/bipolar cap choices, like Nichicon Muse ES (many values) and Elna RBS (fewer), see Handmade Electronics Indexpage for a selection, not crazy expensive. partsexpress (and Solen.ca, but Ca shipping... ;() have cheaper stuff

[wizard333]

Thanks!

Found some at mouser to, they start to get pricey at 22uf but I ordered some anyway just to see what the fuss is about.

[Joey Voltage]

I personally don't like them, and would certainly pick a good quality Low ESR elko over one. it depends on how careful you are with an iron, but wima makes low voltage poly films in large values (which are perfect for PCB use). The leads may be long enough to wrap around the leads of an RK and soldered before being placed in a turret. I also tracked down a bunch of long leaded 10uf poly's a while back for dirt cheap. you just have to look for them