Paper in oil caps

[musiclikscreams]

Been away from DIY stompboxin for about a year or so now and I'm lookin to start back up with an Em Drive clone (tagboardeffects.blogspot.com/2013/01/emerson-custom-guitars-em-drive.html)

I'm just having trouble finding PIO caps. Any help would be tremendously appreciated

[SmoothAction]

Studiozey.com ... 

[FiveseveN]

It'll work and sound just as boutiquey with regular caps, you know.

[psychedelicfish]

^but you won't get all that mojo noise...

[Fender3D]

Here, in Italy I can provide gallons of pure extra virgin olive oil for cheap...
now if you only bring the paper...

[midwayfair]

It'll work and sound just as boutiquey with regular caps, you know.

As long as boutiquey means crappy, which is what the Em Drive sounds like.

[Gus]

I would build that simpe circuit with other caps to hear if you like it.

I looked at the tagboard site and noted the circuit is simple two caps 2 resistors and a transistor.  That type biasing can be troublesome.

Look at the following screenshot of a sim note how the collector voltage changes with different hfe transistors and bias/feedback collector to base resistor values I even have a emitter resitor that helps the em has a grounded emitter.

[musiclikscreams]

so PIO isn't really gonna make a huge difference in tone?  i wanted to build an em drive because i need a transparent drive in my chain and its mega simple.  i have a tendency to start big project and get burned out and never finish em. 

any alternative suggestions?  i got a bunch of vero layin round waiting to be used

[Jdansti]

It'll work and sound just as boutiquey with regular caps, you know.

As long as boutiquey means crappy, which is what the Em Drive sounds like.

What do you recommend for a simple-ish drive that sounds decent?

[pappasmurfsharem]

It'll work and sound just as boutiquey with regular caps, you know.

As long as boutiquey means crappy, which is what the Em Drive sounds like.

What do you recommend for a simple-ish drive that sounds decent?

The EM drive is fine for about 50% of the knobs travel after that it distorts like garbage.

[Gus]

It'll work and sound just as boutiquey with regular caps, you know.

As long as boutiquey means crappy, which is what the Em Drive sounds like.

What do you recommend for a simple-ish drive that sounds decent?

The EM drive is fine for about 50% of the knobs travel after that it distorts like garbage.

If it sounds bad at 50%, one fix would be to use a 100k series resistor into the base with a  100K linear potentiometer this is about 1/2 of 250k

[smallbearelec]

Build an Ursa Minor:

https://www.smallbearelec.com/Projects/UrsaMinor/UrsaMinor.htm

My PC board for it:

http://www.smallbearelec.com/servlet/Detail?no=1391

is less than $8.00. Leave the diode loop open and it is an adjustable clean boost.

[R.G.]

But meanwhile, back at paper-in-oil caps.

I lucked into an old book entitled "Power Capacitors", which contained a history of capacitors used for power applications. It described the manufacture and materials and why those changed over time.

When electricity was just getting started as an industry, they needed caps for AC power line work, telegraphs, etc. They knew from the early experimenters that metal foils separated by an insulator worked, ala Leyden jars.

Glass was expensive, so they tried paper, which worked OK, and would normally withstand the voltage, except for two things. Paper absorbs moisture from the air, which lowers its withstanding voltage, and it contains particles which conduct, and voids. Depending on the paper's manufacture, the conductive particle probability per unit area could be reduced, but not eliminated. So they figured out that is so many square feet of paper had X probability of a conductive particle, then sandwiching two layers would mean that there was essentially no possibility that two conductive particles would line up. That meant that they could make capacitors from two layers of paper and metal foils. But the paper still absorbed moisture.

Someone figured out that they could fill the voids in the paper with insulating oil, and then moisture could not get in. This had the extra advantage of boosting the withstanding voltage and of increasing the capacitance because of the increased dielectric constant of the oil. And bango! Paper-in-oil capacitors were born. Strictly speaking, they are oil filled caps, the paper being mostly something to mechanically prop the metal foils from touching and the oil providing the dielectric constant and moisture immunity.

There were still issues. The paper was twice as thick as it needed to be, which made the capacitors big and heavy. So they waited around til polypropylene film was invented, and started using that instead of one layer of paper. This worked well, the paper still held the oil, and the polypro kept conductive particles from killing the cap. Eventually, when polypro film got better, they realized they didn't need the paper any more, and that the caps could be made smaller and cheaper with just the plastic film, so the film-in-oil capacitor was born. Even later, with better metal foils and films, they realized that the oil could be dispensed with, which was good since there were those nasty poly-chlorinated-biphenyls in the really good insulating oils.

From there it was thinner films and foils, different stacking, etc. to get modern film caps.

[Phorhas]

Yes, all that science jive is nice - but what about tone ?!

PIO caps make me sound way better - equivalent to an extra 20 seconds of practice each day !

[adstrum]

The EM drive clone is pretty unimpressive. It would seem a waste put drop some expensive PIO caps into it. Those caps can add a nice touch to a great pedal, but it's not a magic panacea for ordinary sounding boards.

[Jdansti]

Yes, all that science jive is nice - but what about tone ?!

PIO caps make me sound way better - equivalent to an extra 20 seconds of practice each day !

Wow!  Think of how great you'd sound by practicing an extra whole minute every day!

[musiclikscreams]

The EM drive clone is pretty unimpressive. It would seem a waste put drop some expensive PIO caps into it. Those caps can add a nice touch to a great pedal, but it's not a magic panacea for ordinary sounding boards.

Thank you, I was looking for a straight forward answer. Thanks for all the input guys. I think I'll slap one together with just plain ol caps and see how it sounds

[tca]

^ I've breadboard it with plain caps, it sounds as it should: good with a big boost.

Cheers.

[midwayfair]

any alternative suggestions?  i got a bunch of vero layin round waiting to be used

Do you just need boost, or do you also need dirt from the pedal?

-The beginner project here is dead simple and nevertheless impressive sounding.
-Smallbear's Ursa Major that Steve linked to will have far, far better distortion than the Em Drive with only a couple extra parts.
-AMZ's Mosfet Booster or Micro Booster are both excellent transparent boosts (if you don't need more dirt). I also love the Madbean Fatpants.
-Shameless plug: the "Clipper Ship" project on my web site has gotten some good marks from a couple people I trust. It's a little more complicated than the other three but will do just boost or just dirt as well. (And there's a PCB for it.)
-Not that I condone such things, but there are layouts for certain legendary "transparent overdrives" that only use a single dual op amp and have good bass and treble controls. The parts count is also really low on that one.

[psychedelicfish]

^ The AMZ MOSFET boost with its gain on full has some decent sounding dirt to it