With metal ones, the sheath is the +, but if you chassis ground then you're connecting + to ground, not a good idea at all. Am I the only one who uses metal DC jacks? It's funny, normally I use plastic sheathed 1/4"s and metal DCs, while I can imagine for most others it's the other way around.
-Colin
No, you're not the only one.
I actually rather hate having + rings, but it's the industry standard, probably for one reason: you can get DC jacks that switch if you stick something in there. They switch between battery and adapter power with only one switch, and it's good practice to switch + supply, not ground for this.
The switching contacts always are the outer (sheath, rim) ones for mechanical reasons: so power supply switching (disengaging the battery when using an adapter) dictates using a + outer rim.
I *prefer* a negative rim though - in DIY the chassis usually touches the DC-jacks rim, so... If you want to use regular metal-on-the-outside type DC jacks, prepare to isolate them with an elaborate array of rings and buffers: you don't want the chassis to sit at +supply voltage (although it could work)
uhhhhh... dont use the metal ones use plastic.
there is no other way arround it, unless you want to insulate it yourself. you could also use a non standard adapeter, or use a rat style plug.
The method I use involves a DC jack with an insulated bushing, for instance this one:
Mouser #163-4302
I use the metal ones, and use chassis grounds.
So, how do I get around that problem? I partially wrap the threads w/ electrical tape, where the jack passes thru the enclosure. Then, I take two o-rings, and place them on the jack. One goes on the outside, and one on the inside, mounted so that they isolate the jack from the enclosure. I tighten the nut just enough to keep the jack in place and not totally squish the o-ring. This has been working out pretty well for me and I have been using this method for about 18 months now.
I have also been known to drill an oversized hole in the enclosure and then actually mount the jack in a non-conductive plate, like a piece of non-padded perfboard or something, which in turn gets mounted to the enclosure. This works very well on certain kinds of enclosures that I have used in the past.
Quote from: Paul MarossyI use the metal ones, and use chassis grounds.
So, how do I get around that problem? I partially wrap the threads w/ electrical tape, where the jack passes thru the enclosure. Then, I take two o-rings, and place them on the jack. One goes on the outside, and one on the inside, mounted so that they isolate the jack from the enclosure. I tighten the nut just enough to keep the jack in place and not totally squish the o-ring. This has been working out pretty well for me and I have been using this method for about 18 months now.
I have also been known to drill an oversized hole in the enclosure and then actually mount the jack in a non-conductive plate, like a piece of non-padded perfboard or something, which in turn gets mounted to the enclosure. This works very well on certain kinds of enclosures that I have used in the past.
That's exactly what I did, except mine involved more electrical tape and less plastic bushing.
-Colin
I only use the metal ones for builds that I want the negative to be grounded. Otherwise, to me at least, its just to big of a pain in the ass to try and get around it not touching the chassis, so I just use plastic.
'Scuse me for being such a Neanderthal, but...
I use miniplug jacks as dc adapter jacks, you know the common audio type but mono of course. Some are metal, some are not; the box is connected to the jack mechanically and electrically in the first case.
I dont take any special care on PNP boxes, +9v run all over the enclosure as I understand. I tried negative gnd but I get this ugly white noise when turning down the vol. pot.
How succesful have I been? My pedals have worked for like 20 months in some cases and had no problems. I used to run them on a regular wall wart but now I use a regulated supply. I HATE batteries and never use them. I RECORDED THEM, no noise or loop or any kind of problem. Used them live too. What could possibly go wrong? Thanx for the information.
Personally I prefer the plastic DC jacks. They're easy-to-use (wink wink ;) ) and readily available. Plus there's no problems with insulating them from the box.
steve at small bear has a good tip, he drills large, then uses bondo
and redrills......check it out.... :D