1uf polarized vs non-polarized

[Seven64]

so i read often that replacing 1uf electrolytic caps with unpolarized film caps can improve tone/sound quality.  does this have any merit?  i am asking specifically about the 1uf e-cap in the amz jfet buffer.  does it double as some sort of polarity protection as well?  could i just use a film cap instead?

[aron]

You can use a film cap, no problem.

[Seven64]

just got it togeather but there is a high pitched whine.  could that be the problem?

[R.G.]

No.

[Seven64]

this is the 3rd time i have built this circuit and have never had this problem.  i have triple checked everything.  could i have heated the transistor too far?  i just figured it wouldn't work at all if i had burnt up the transistor tho.

[R.G.]

this is the 3rd time i have built this circuit and have never had this problem.  i have triple checked everything.  could i have heated the transistor too far?  i just figured it wouldn't work at all if i had burnt up the transistor tho.

Whine is either the circuit oscillating or being fed in from the outside, possibly by a power supply or some other effect on the same power supply (which includes ground).

[Seven64]

i ripped it apart and am trying again.  but i have a seperate power supply for my prototyping area before anything makes it onto my pedal board.  i just untangled it from its mess within 4-5 instrument cables and a laptop charger.  could it have anything to do with me switching around a layout.  i used this layout:

http://www.aronnelson.com/gallery/main.php/v/diyuser/Sundgist/Jfet+Buffer+Stripboard.gif.html

but changed the g and s strips so that the 2n5457 would sit in it naturally without bending pins.  i switched all the components honoring what it connected (d to g, s to grnd etc), but have never had this wining problem before, and it has been tangled up many times.

[R.G.]

... and a laptop charger...

[Seven64]

moved the power supply to its own wall outlet not shared, built an entire new buffer with the correct layout with the bent pins, and it has the same problem.  plugged in a pedal to see if it would make the same sound and it doesnt.  could it be a bad 9v plug?

[R.G.]

Have you tried it on a battery?

[Seven64]

just did.....no problems.

edit...

plugged it into my pedalboard power supply, no problems at all with the same 9v plug and a different 9v plug.  both plugs had the ring when i used my bench power supply.

[Paul Marossy]

One argument you could make for using a 1uF film cap in lieu of a 1uF electrolytic cap is longevity. A film type cap won't dry out in 25 years, although I have yet to run across an electrolytic cap that has dried out in anything that is 25 years or older in any other section other than a failing power filtering capacitor. OK, I guess one exception is that 4.7uF cap that goes bad in wah pedals sometimes.

[DavenPaget]

One argument you could make for using a 1uF film cap in lieu of a 1uF electrolytic cap is longevity. A film type cap won't dry out in 25 years, although I have yet to run across an electrolytic cap that has dried out in anything that is 25 years or older in any other section other than a failing power filtering capacitor. OK, I guess one exception is that 4.7uF cap that goes bad in wah pedals sometimes.

High usage or high capacitance capacitors tend to dry up faster .
High usage means It's being used somewhere where it's always working 100% of the time or High duty like power supply filtering caps .
Unfortunately it's both high capacitance and high duty and high usage for power supply filtering caps .

[thedefog]

One argument you could make for using a 1uF film cap in lieu of a 1uF electrolytic cap is longevity. A film type cap won't dry out in 25 years, although I have yet to run across an electrolytic cap that has dried out in anything that is 25 years or older in any other section other than a failing power filtering capacitor. OK, I guess one exception is that 4.7uF cap that goes bad in wah pedals sometimes.

I guess it depends on what you work with. I'm constantly replacing larger value electroyltics in power filtering sections of old synthesizers and pedals.

[Paul Marossy]

Yeah, it's quite common for the electros in power supplies to go bad. I was referring more to stuff like bypass caps on transistors, in the signal path, etc. I can't think of one instance where I had to replace one because it was bad. But in power supplies, yes, all the time they go bad. Like already mentioned, they have to work the hardest.

[Seven64]

i have had to replace one in a wah pedal before.

thanks guys!  im glad i got my buffer working, and figured out that my power supply has some issues.   

[thedefog]

Yeah, it's quite common for the electros in power supplies to go bad. I was referring more to stuff like bypass caps on transistors, in the signal path, etc. I can't think of one instance where I had to replace one because it was bad. But in power supplies, yes, all the time they go bad. Like already mentioned, they have to work the hardest.

Yep, only in power sections I've had to replace them. Sometimes smaller value ones if they're doing small voltage filtering.

[Ice-9]

From all this talk about capacitors failing in different circuits and a HUGE amount of tonal variations between different types of caps I draw the conclusion that we should never use capacitors as there rubbish.

[R.G.]

Electrolytic capacitors degrade by
(1) time when not polarized by a voltage; the oxide insulator dissolves over a decade more or less into the electrolyte
(2) heat; heat speeds up the chemical degradation of the oxide layer in (1) by about 2x for every 10C rise, as well as changing the conductive electrolyte

A polarized cap kept at the rated voltage by DC will last semi-forever. Left with no polarizing voltage, one to a few decades. Reverse polarized, minutes down to milliseconds.

Power filter caps have significant AC currents running through them. This AC current through the equivalent series resistance (ESR) heats the insides. This is why capacitors are rated for maximum ripple current - the internal self heating shortens their lives.

External heat sources can do much the same thing.

[amptramp]

From all this talk about capacitors failing in different circuits and a HUGE amount of tonal variations between different types of caps I draw the conclusion that we should never use capacitors as there rubbish.

One of the great tube gurus agrees:

http://greygum.net/sbench/sbench/norchv.html