Quick tantalum cap question

[Al Heeley]

There's a low value tantalum cap called for in the bassballs project, my usual UK outlets don't have it - is it ok to substitute a different type like a ceramic cap, or is the polarity of the tant caps vital for the function/performance? The project specifically calls for 2 tantalum caps.

[Gus]

What bassballs project?

  It depends post a link

[Al Heeley]

This one:
http://topopiccione.atspace.com/PJ08EHBassBalls.html 

[Gus]

.47uf and 4.7uf?

The .47uf  is part of the high pass to filter sweep opamp part, a .47uf film should work fine.

The 4.7uf matters for the RC time constants.  The attack is set by the 100 ohms series into the cap and the decay by the 330K and the 2n5088 transistors input resistance parallel with the cap.

I GUESS EH used a tant at the spots because of better tolerance (cap value) and more stable cap value with a tant caps lifetime.  Yes an Al electro will work at the 4.7uf but measure it's value if you want it stock.

That posted, an attack mod is to replace the fixed 100ohm with say a 47ohm fixed wih a 100 ohm trim pot for 47 ohms to 147 ohms.

[Al Heeley]

Thanks Gus - never ceases to amaze me the knowledge of the members on this forum!

[puretube]

Low(-er) leakage...

http://www.tpub.com/celec/54.htm
avx...
kemet...

[Gus]

The decay R is less than 330K so leakage should not matter that much.
 
Al Heeley asked if something could be substituted for the tantalums that are not readily available in this case.