I wrote up this article about using shileded wire. Pics expralin better than words!
I kept it simple for now.
I also plan to write up an Effects Basics article with tools and materials to use.
If anyone wants to chip in let me know.
http://www.mrdwab.com/john/Shieldedwire.html
John
That's cool John and nice photo's.
For the less experienced, I would have mentioned "how" to wire it up and "why"
you leave one end of the "ground" braid unconnected ! :icon_wink:
MM.
Basic, you do your shielded wiring very similar to the way I do mine. I pull the shielding back like that, but I wrap my wire the opposite way, so that it points out the back end of the heatshrink. I'm sure your method works just as well :D.
Thanks marty
I did forget to show the other end and mention about only shielding at one end. Sometimes in getting it all on the page and with links and photos I get a bit of tunnelvision and just need to get it out there first... then fix the problems and omissions!
Cliff
I do things like wiring looms for patch bays with the ground wire coming out the other end. It's stronger and has more strain relief...For the inside of a pedal there isn't much wear and tear... Same thing really though...
Are you going to make a how-to on making those wood enclosures? I'm really curious how you join some of those. I've always been a big fan of using enclosures other than the Hammond cases and I've got quite a few oddballs myself.
I do it a similar way, I believe I started doing it after reading kevin O'connors(London Power) books, but I could have picked it up somewhere else- Push the braid back like you do to loosen it, but rather than undoing the braid, I simply reach in with some needle nose pliers, spread the opening between the braid enough to reach around and through with the pliers, and sort of bend the inner wire out through the opening in the braid. Leaves the braid mostly braided when you're done.
In situations where having an unshielded ground wire hanging around isn't an issue, it tends to be easier if you want a longer length of braid than inner conductor since you don't have to un-braid a whole bunch of the sheild. That said, your method (particularly the tidy way of attaching a wire to the braid) looks a lot better for 90% of the situations I can think of.. I'll have to pick up decent shrinkwrap and give this a go next time I'm working with shielded wire.
Thanks!
Hey this is great, thanks. I just came on here to find info about using shielded cable. Okay, dumb question: would there be any benefit to using shielded cable on power runs, e.g., from +V of the adapter jack to the board?
Quote from: zarathustra on January 16, 2007, 11:18:39 AM
Hey this is great, thanks. I just came on here to find info about using shielded cable. Okay, dumb question: would there be any benefit to using shielded cable on power runs, e.g., from +V of the adapter jack to the board?
I don't think so. At least I haven't ever seen a builder do that.
The idea is to shield audio signals from inductance. The shield gives inducted noise a path to ground.
This thread would be a good place to post your pictures of shielded wiring.
Some "inside the box" pics would be a helpful addition to BasicAudio's pic tut.
Ok, I updated the page a bit. Added a couple more pics and clarified some things. Any place you have a high gain high impedance wire run that is longer than a couple inches will benefit from shielding. I know almost all the vintage effects did not use shielding but it's a goos practice to use.... It can't hurt!
Thanks for the help folks!
I plan on doing a tool and equipment/thingies page as well.
sfr
I haven't tried to make the wires with the inner conductor pulled through the braid. I have seen it done, I just never have done it that way. I'll have to give it a try.
Cliff
I may do a wooden enclosure page. I have to make some new boxes soon so it's it's just a matter of snapping a few pics and cobbling it together. It's actually something I have been meaning to do at any rate...
John
BasicAudio:
Maybe some explanation of why the shielding is necessary and how the wirewrap accomplishes it? E.g., do the signal-carrying wires have to be shielded from each other, or just from other wires in the circuit? That could be relevant if, say, one had shielded wire with multiple wires running inside. I once made a guitar cord out of an old PC keyboard cable. It sounds dumb, but it's really heavy duty (and I was desperate at the time) and works great. Just soldered some jack ends on it. But I noticed that inside there's about 10 individual wires with a reasonably heavy foil wrapped around the whole thing. The guitar cable only needs 1 signal wire and 1 grd wire, of course, but if one wanted to, could you run signal down the other wires without interferance? Or does EACH signal-carrying wire need to be shielded from every other signal-carrying wire?
Just curious. Anyway, great website tutorial so far. And I nominate your house (if that's it in the photos) as the site of the next DIY Stompbox Convention. We'll leave it just as we found it :icon_twisted:
Thanks for the advice iddlecatterbox
I will be adding to the site as I think of things. The singal carying wire that are longer than a couple inches can benefit from shielding. It really depends on the gain of the device. With a guitar cable you have 10 or more feet of cable with a tiny high impedance signal which get amplified by a lot through your amp. Any noise in the cable and you'll hear it for sure. This is to a smaller extent in the pedal with the exception that there are amplifying devices in there and more of the time unshielded wiring.
Basically the wire that connects to the iput jack tip is an extention of you guitar cable. It will work without being shielded but depending on the invironment you play in ( lighting giving off radiated noise, transformers or other electronics nearby, etc etc) you may need the shielding more in certain invironments. At home maybe there are no gremlins getting into your audio signal. But then at the studio, practice space, a gig, there may be less than ideal conditions where the shilding can keep the audio cleaner.
A lot of pedals in and of themselves, and depending on how the layout is, will benefit from using shilded wire. Think of how many ways you can wire a pedal, where the wires cross, where they run compared to the others. In tube amps a lot of the work in making and amp sound right (no noise/hum and a full sound) is in the way the wires are layed out. It's called "Lead Dress" how the wires are routed throughout the amp or pedal.
Pedals are a lot more tolerant of bad lead dress. It's not so much how clean things look under the hood as much as how certain elements of the amp/pedal should not come into proximity with other areas. Pedals are low voltage, not to mention contained in a small area with shorter leads and the components are almost always on the board as oppossed to tubes which have wires running to them.
Places to get shielded wire:
Old tape decks, VCRs, surplus RCA cables. Some of this wire is better than others of course but what you want is a tight braid that covers the whole inner conductor. The more the inner wire is covered the better. Be carefull soldering this wire because if the insulation melts you wire have a short to ground and a non working wire. As a mentioned I use teflon wire for this reason. You can find teflon wire on ebay as well as teflon shielded wire. It's obviously more expensive but it's the real deal and if you are looking for better quality then this is it. There is a guy on ebay who sells nothing but teflon wire.
John
i'm still a little confused about the connecting only one end thing. doesn't that leave a floating ground, i.e. hum?
No, if you're connected at one end your shielding is still grounded. You connect only one end to prevent potential ground loops. Keep in mind, this is in the context of inside the device where the grounds can become redundant, not for a guitar cable.
This is assuming you are (for example) connecting a shielded cable to a jack socket that is not insulated from a metal chassis which is connected to GND. In this case generally you'd connect the shield to one socket to make a GND connection to the chassis. Personally I use Cliff S2 sockets that are insulated, so the ground has to be connected to all sockets.
For going from PCB to POT to PCB you can leave the ground disconnected at one end, but often you'll need the GND connected to the CCW lug of the pot.
Stew.
Nice How-To.
I just heat shrink the twisted braid, larger heat shrink where the two wires split, and am good to go. I'll have to try your method sometime.
The Shiled at one end brings the shielding element all the way from one end to the other but not touching at the the other side. Sort of a telescoping shield. It's only at one end to protect the sensitive wire against picking up noise etc.It is not a ground to connect the circuit flow as in a guitar cable.
john
From an auction for an older Cornish NG Fuzz...
(http://img.auctiva.com/imgdata/2/3/2/4/0/3/webimg/32264280_o.jpg)
Wow! That's some seirous shileding going on.
I might have to charge more to afford the extra heat shrink and cable ties for that kind of work!
Cool.
John
Guys how important is this sort of shielding once i use a box made of steel?
It really depends on the circuit. If there is no power transformer and only DC power inside the pedal, and you keep the input and output wiring seperate you don't generally need shielded cable. IMHO If anywhere, the place to use shielded cable would be from the input socket to the gain stage in a high gain pedal.
Stew.
John,
Thanks for all your work.
A very useful article.
I have a JFet Vulcan that needs shielding very badly.
Regards
Carsten
The box material whether steel of Aluminum isn't much of a concern for low voltage pedals. With amps it plays a part sometimes...
Shielding is not always about keeping things outside the box out of your ciruit. Sometimes you need to keep things inside the box separate and from others and sometimes shielded. The input and output wires should always be separated by the most distance you have to work with. ANd short as possible.
95% of the time if you shield the input lead from the jack to the switch and then to the board you will be fine. Then possibly the output jack leads if you want to go further.
John
Shouldn't it be irrelevant how long the leads are IF they are shielded properly? Or am I missing something? ???
Well it depends how you look at it. If you have short leads you may not benefit form shielding. But if you have long shielded leads it shouldn't make too much difference how long they are within reason. Shielding anything less than a couple inches long (assuming it's not too close to anything which will make it osciallate is not going to do too much.
It's better to solve the problems before putting on "band-aids". There a many high gain builds with no shielded wire. But the layout of the board and the pots has to be very strictly followed. With a small box often times this is hard to do, although short wires are good!
Some things to watch out for:
Keeping the input jack lead away from the output jack leads. They get close at the switch of course but as much as you can sepatarte them elsewhere the better. What is happening is that with enough gain you will create a feedback loop and you will get some squeal (or possibly even worse as you can't completely hear it) it will effect the frequency responce and you may not notice that it's happening. The higher the gain the more this become crucial.
Wires from gain controls, volume and to a smaller extent tone controls should be laid out so wires are short and not parallel and running along high gain wires such as volume and gain controls. It's a bit confusing but basically keeping things neat will go a long way.
Laying out the circuit so the input is on on side and the board lays out from on side to the other is a good way to go. This way the controls are in order somewhat and don't cross over each other. Wiring straight from the pad to the pot neatly.
When wires leave the board they become antennas for noise and oscialtion.
John