1uf tantalum v electrolytic in a klon based of pedal

[Mark Hammer]

Once upon a time, tantalums tended to be smaller for a given capacitance and voltage rating, than their foil cousins.  In other cases, they might have been used simply for physical convenience.  So, for instance, MXR tended to use them because you could easily lie them on their side and fit a low profile board in a 1590B over top of a big stompswitch and big pots.

But both those physical advantages have generally disappeared over time.  You can get some pretty dang small foil electrolytics with high capacitance/voltage ratings these days.

[R.G.]

As I said, I wondered if they had a longer lifespan than electros, from your post I'm assuming the answer is "no".   Just something I've wondered for some time, thanks for clearing it up. 

I was surprised to see the item from engineer's edge saying that they do not have the same shelf life wearout mechanism as aluminum.

It would be nice to find a small 4.0uf film cap to use instead, but I've never found one that is small enough for commercial wah boards.

Do what I do - glue four box type 1uF films together. 

[familyortiz]

I thought I'd add one thing here, about tantalum electrolytics, and it's based on bringing up designs for production in an industrial setting... the number of out of box failures is rather high and due to manufacturing flaws. The relevance for us DIY'ers is that you may get a few for a design and one may fail showing leakage (indicated by a low resistance across the cap) or an outright mini campfire, even without a negative polarity event. I am sure there are statistics on this. In either case, they can fail suddenly, much like anything else.

[fpaul]

I built a calrec equalizer clone I found on the Gyraf audio site.  It uses a few 33uf tants.  I read a thread where Gyraf said he built it using tants and electros and the tants definitely sounded better, so that's what I used.  I'm guessing I couldn't tell the difference myself but I would hate to always be wondering if my unit has an inferior sound. So I found some cheap on ebay.

[R.G.]

I'm guessing I couldn't tell the difference myself but I would hate to always be wondering if my unit has an inferior sound.

This is the basis of the classic FUD maneuver in the old computer mainframe sales industry. "FUD" stands for "Fear, Uncertainty, and Doubt". If you plant the seed of "uh, if I go against what the salesman is saying, I could find out I'm wrong later. I'd better do what he says." Three Initial Corporation ran on that for a long time. It exploits a basic human weakness, and is very effective.

[wavley]

Well, I work with microwave stuff as my day job and we use tantalum caps in bias supplies because of their low ESR and low parasitic inductance.  On paper, this seems ideal for power supply decoupling and with the military grade stuff we use here reliability does not seem to be an issue... BUT, when I worked in pro audio repair, it was pretty much a given that if you had a circuit that didn't work and it had tants in it, then look at them first and A LOT of times they were the problem.

That said, I don't really like the way they sound in "Clean" circuits as coupling caps and tend to use an aluminum electrolytic bypassed with a film when I need something that big, otherwise I just use a big film when I can.  There is a bit of grainy distortion like with a ceramic.

When I was messing around with my Distortion+ the other day, I have to say that it didn't make much, if any, difference between tant and aluminum, aluminum bypassed by film gave just a tiny bit more definition, but not enough to bother with if you were making more than a one off or, like in my case, modding an old pedal to tailor it more to "your" sound.

[greaser_au]

Well, I work with microwave stuff as my day job and we use tantalum caps in bias supplies because of their low ESR and low parasitic inductance. 

They were all the rage in [LS]TTL 'glue logic' circles 25-odd  years ago for those exact qualities. Basic design rule of thumb was a 0.1u monolithic cap hard up against each package, & a 10u tantalum  on each row to deal with the output switching transients of the totem pole outputs. Both capacitor types are physically small so added benefits are that they take up little PCB real estate and leads can be short. MOS doesn't behave the same way so this method is much less prevalent now.

Aluminium electros have higher inductance & ESR, so you usually need to include a parallel film or ceramic cap in higher frequency applications. Physical size can be an issue, & as equipment ages,  the low value, high voltage electros are often the first place to look for failures. However they are inexpensive!

There are all sorts of reasons to choose one type over the other, but in the audio chain of pedals you are likely safest using film caps or aluminium electros. 

Steve Bench's 'The Sound of Capacitors' article is some interesting reading material on this topic... http://lmgtfy.com/?q=the+sound+of+capacitors+steve+bench  (BTW I'm not making fun of anybody with this link, I just like spreading the lmgtfy site - it's a kack!!!)

david