How to insulate jacks?

[tempus]

Hey all;

I've been reading R.G.'s suggestions for reducing ground loop hum in amps. One of the first things he suggests is to isolate the input jacks from the chassis. Does anyone have any suggestions for ways to do that? I've been thinking about surrounding the mounting hole with electrical tape, but I'm wondering if anyone has any better ideas.

Thanks

[phector2004]

You can buy isolated jacks 

[davent]

You can also get plastic/nylon shoulder washers that will isolate the jack from the chassis. Tape's a failure waiting to happen.

dave

[Earthscum]

To answer the SL... The same way you insulate Tom, Dick, and Harry's. Layers of clothing work great. 

Does anyone have any suggestions for ways to do that?

I can tell what NOT to do, and afterwards you'll know why I can never use a rubber grommet again...

Really, don't try to use rubber grommets... to thick and squishy.  I had to do it in a pinch (no pun intended).

I've done the E-tape thing a couple times and it works well. What I did was went about 1/16" bigger hole, then took strips of tape and wrapped them around through the hole, stretching them a little bit, until I had a loose fit. Then I cut a piece of heat shrink about 1/4" long and fit it around the jack itself. I used a lighter to shrink it, pushing it as far on to the jack as I could so it mushroomed against the back a bit. Then I stuffed it through, got the lighter out and hit the end to warm it up and get it to stick to the tape a bit and stuffed the washer and nut on it and cranked them down while it was still warm. Then I used an exacto knife and cut just a hairline outside fo the washer, peeling each piece of tape off as I went so I didn't just gouge through to the paint.

Done, and sealed. Still holding up, but had to do a repair and found that it was a pain to get out and back in. 

[chi_boy]

Would these work?

Mouser:
561-SW375 - Nylon Shoulder Washer
561-D37562 - Nylon Flat Washer

[davent]

Would these work?

Mouser:
561-SW375 - Nylon Shoulder Washer
561-D37562 - Nylon Flat Washer

This Wiki entry has the Mouser part numbers and it's a match! Also some other options.  The issue with the washers is whether the jack bushing will be long enough for the thickness of the enclosure+nylon washers+metal washer(s)+nut.

http://www.diystompboxes.com/wiki/index.php?title=DIY_FAQ#JACKS

dave

[tempus]

OK, thanks for the suggestions. I had seen those washers from Mouser before, and that was an issue I wondered about. I'd rather not have to enlarge the mounting hole if I can avoid it. Never thought about the heat shrink though. That's a good idea too. I might try the tape first to see if/how much of a difference it makes in my case before ordering.

What about coating the hole with something non-conductive? Has anyone ever tried that?

[defaced]

You want fiber shoulder insolation washers. They're made by Keystone. I buy mine through Mouser.  I don't have a part number handy, but download the catalog, look in hardware and under Keystone.

[smallbearelec]

I don't have a part number handy

Keystone #3069

http://www.smallbearelec.com/Detail.bok?no=133

Regards
SD

[tempus]

Those fiber insulation washers look like they'd do nicely. Thanks for the part # and the Small Bear link.

Now, for your typical amp panel thickness, I'm assuming that you'd need 1 shoulder washer and 1 flat washer, or do you need 2 shoulder washers (1 for each side)?

Thanks again

[tempus]

One other question about the fiber shoulder washers - do you find that you have to widen the mounting hole or do they usually just drop right in?

Thanks

[smallbearelec]

do you find that you have to widen the mounting hole or do they usually just drop right in?

I don't do amp work. However, I have actually looked at these and compared with Switchcraft bushings. You definitely have to widen the holes for the jacks and it looks to me like you would use two washers.

[davent]

If the chassis wall is thick enough you would use a shoulder washers inside and out but if it's your typical Hammond chassis the walls are too thin, you'd use the shoulder washer inside the chassis and a flat fiber washer on the outside of the chassis. You have to increase the hole size so that the shoulder fits into the hole. Switchcraft jacks need an ~0.375"  chassis hole and the Keystone washers i have need a 1/2" hole so if you have a step bit it'll be very easy to open up that hole to the necessary 1/2". I've always found it necessary to thin out the flat washers to leave enough bushing exposed for the nut. (you'll also have a thin metal washer between the fiber washer and the nut.)

dave

[digi2t]

Switchcraft has insulating shoulder washers specifically designed for 1/4" jacks. The Switchcraft p/n is S1029, and the Digi-key p/n is SC1147-ND.
PDF Cad file is here;
http://www.switchcraft.com/Drawings/s1029_cd.pdf

I used these to insulate my expression pedal jacks for my Gristleizer, on a Hammond 1590DD enclosure. You widen the hole, and use 2 washers, one each side. They are thin enough to still give enough thread for the metal washer and nut. Work puuuurfect.

Cheers,
Dino