Post by ssstonelover on Nov 11, 2007 21:27:10 GMT -5
Twisted pair wiring is common in various industries, such as telephone, and is certainly a popular way to reduce electromagnetic interference (EMI) going back over a hundred years and as such is a valid way to reduce 'noise'.
Interestingly enough there is UTP (unshielded twisted pair, suc has what Chris is talking about) as well as STP (shielded twisted pair)
As to whether a shielded cable or a simple twisted pair is better for the run frm the jack to the control cavity.... either in theory or in practice, perhaps ChrisK, Sumgai or one of the heavyweights of the board can weigh in... I've been curious about that myself for some time.
As a kid I remember working with my father, who was also an electrical engineer, making twisted pair cables. He held the 1/4" drill, I had the pliers (now dang it, hold on!).
If you do need a short run of shielded cable for a couple/few inches, I'd buy an audio phono plug cable for a couple of dollars and just cut and strip it as needed.
I actually use Teflon insulated silver (as in real) plated mil-spec #20 AWG stranded wire for all of my guitar and amp wiring.
Why, 'cuz it was free back when I designed systems for the military back in the 70's. A 200' 150 conductor cable that had just been fabricated was found to be faulty on several pair and was disposed of in the dumpster (and probably written off). I still have more than a bit of wire left.
Diving, dumpster, is.
Say what you want, there were years where I made more on surplus sales than in salary.
Post by ssstonelover on Nov 13, 2007 19:36:44 GMT -5
Hm...on the side going under the tone control or the one used to solder and create the star point?
The star point side can be pretty small, 5-10mm OD (outer diameter). Smaller is better than bigger here... easier to heat up and solder, insulate afterward, etc. The other side, the ID (inner diameter needs to be big enough so the threaded part of the shaft of the tone pot fits through.... and that is about 10mm (.3875") [3/8"] ...
These should be avaiilable at Radio Shack, Frye's, etc, so if you decide whatever you have is too small or too large, you can quickly get an alternative pretty cheap.
I know there has been a lot of discussion regarding the .033 600v cap needed for QTB, and I have done all of my guitars using one. I have a gig on Friday & need to get my other guitarists Strat done. I am waiting on caps in the mail, but doubt they will reach me in time to finish. Can I sub a 50v in the meantime, or do any of you have other suggestions? My guitaris & I don't get along too well (lol) so aside from possible death by electrocution, what other problems will this cause? Thanks, Bill
Thanks for the quick response........my guitar buddy is forever in your debt! I will try DigiKey tonight. I am a longtime user of GN1, but fell off the planet not too long after John had problems w/ the site. Glad to be back.
I was looking over Johns S-Tastic mod, and he uses a different cap & grounding scheme there.
He writes; "Also note (from the accompanying photos) that I used this modification to test a slightly different approach to the problem of isolating the strings. Instead of using a very large capacitor between signal ground and all of the shielding, I used a fairly small (0.1uf) cap between the cavity shielding and the string ground. The smaller capacitor provides a little more protection from AC shock (see the article on shock hazards). The smaller capacitor is also physically smaller, making it easier to position in a tight body cavity, and more readily available. This approach does have a drawback, though – if metal knobs are used they may not be isolated. As far as noise rejection is concerned, this scheme worked at least as well as isolating the entire shield through an 0.33uf capacitor."
Besides metal khobs & switch tips not being isolated, do you have any thoughts on this?
One last question & I will quit the rambling. If I understand the use of the cap in the original QTB, it is to eliminate "shocking " results and John also mentions using a smaller cap can be noisier. In the S-Tastic text he says you could eliminate the cap altogether & use straight wire or ground all signal grounds to the back of 1 pot. As long as you don't use jumpers between pots, how does the smaller cap or other options effect noise??