Hi,

I'm working on a modified BOSS HM-2 which uses gyrators for tone control. It has an odd capacitor value (C35) of 1.5uF. I happen to have some tantalum caps with this value. Then I noticed the C35 polarity on the BOSS schematic is opposite to some schematics you can find online.

I did an LTSpice simulation which shows the signal polarity reversing.

Assuming my simulation is correct, my question is: Will a tantalum cap stand up to this abuse? Otherwise I have a "normal" 1uF electrolytic that measures 1.2uF and I might use that.

 

My experience with tantalums is that they are not tolerant to polarity reversal. AVX has this study of the effect of 10% reversed polarity: https://www.avx.com/docs/techinfo/17_Reverse.pdf

I don't see any reversed polarity in your simulation. Could you consider a 2.2 uF and 4.7 uF non-polarized in series (about 1.498 uF)?

 

Electrolytics (including tantalums) are normally polarized, have a wide tolerance, and are thus not well suited to use as frequency determining components in audio circuits (they are okay for power supply filtering).
Much better to use a film capacitor, even though they are physically large.

 

My experience with tantalums is that they are not tolerant to polarity reversal. AVX has this study of the effect of 10% reversed polarity: https://www.avx.com/docs/techinfo/17_Reverse.pdf

I don't see any reversed polarity in your simulation. Could you consider a 2.2 uF and 4.7 uF non-polarized in series (about 1.498 uF)?

Thanks, I kind of expecting that. But I didn't think of the excellent suggestion to use series caps. I've read somewhere that if you put polarized caps back-to-back you get a NP cap. But there was a price to it which I forgot. Anyway, I think I'll be going this route, thanks again.

Electrolytics (including tantalums) are normally polarized, have a wide tolerance, and are thus not well suited to use as frequency determining components in audio circuits (they are okay for power supply filtering).
Much better to use a film capacitor, even though they are physically large.

The biggest film capacitor I have is 1uF and it's indeed large. Since this is just a one-off I can hand pick one that is good. I went through my bag of 1uF elco caps to find the 1.2uF I mentioned earlier and most are actually quite close, within a few %.