monradon
Meter Reader 1st Class
Posts: 52
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Post by monradon on Mar 22, 2007 12:12:49 GMT -5
I am getting confused If you are not using shielding its OK to use the back of the pot as ground right If you are shielding using that ground causes ground loops ?? When I draw the circuit out I can not see the difference when shielding because the pots ground them selves to the shielding right Any recommendations of reading would help , I thought I was good at electronics but this one is going over or through my head.
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Post by dd842 on Mar 22, 2007 13:08:25 GMT -5
..... If you are not using shielding its OK to use the back of the pot as ground right ..... right! provided your pots touch the shield, you would already be grounding the pots, so yes. right! I think ... if'n I'm inferrin' what yer implyin' At any rate, the QTB instructions state: "Remove any wires which are soldered from the shell of one pot or switch to the shell of another. These wires are ground loops because the bodies of the controls are also electrically connected through the foil on the back of the pickguard."wrong! as far as I can tell it turns out you're good at it! Dan
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Post by sumgai on Mar 22, 2007 14:23:41 GMT -5
monradon, If Dan gets any better at this, unk, Chris and I are gonna have to put our marbles back in the back and go home! He's right in everything he says, but I'd like to hit a bit more detail. Ground loops, inside of our guitars, are probably too small to cause any concern. On the other hand, there's no practical reason not to eliminate them, it's just good engineering practice. That said, if your pots are touching the shielding material on the pickguard, and if you solder a wire between the backs of each pot, then you have indeed created a ground loop, no matter how small it might be. The obvious cure is not to cut away the shielding, but to simply not solder the wire to the pots in the first place. However, there are two reasons commonly given for not using a pot's back at all. One is that you risk damaging the resistance element inside, should you use too much heat for too long, in an attempt to make solder flow. Personally, I could see that only if you're using a 200 watt soldering gun, the old style we used to use in the '50s and '60s. That might wreak havoc, to be sure. The other reason is that some folks feel that depending on the pot-to-shield contact for a ground is not good enough. By that I mean, there is often a star lock washer on the pot's shaft, so the amount of material that contacts the shielding material is "iffy" - there may be too small a contact patch, in the opinion of some technicians/engineers/others. I can buy that. Some pots are rather flimsy, and may be built of materials that don't conduct electricity very well at all (even in the small quantities with which we deal). That could add some resistance to the ground side of the circuit, thus reducing the shield's effectiveness. It could even get worse....... have you ever looked at how the back of a pot is held on? There are some little tiny tabs folded over - where do they touch? If it's on the ceramic insulator material, then no electrical contact is made, and at that point, the shield is not connected to ground at all. A double whammy. Most good quality bots (Alpha, CTS, etc.) are not likely to have these "qualifications", but many cheapie overseas pots are questionable at best, and in more than a few cases, they are downright insulting to our sensibilities. Those who are truly anal about ground loops will solder an individual wire to the back of each pot, for shielding purposes, then run those wires to a common lug/terminal that is well-connected to the cavity shield. Personally, I don't subscribe to this method. I feel that the pot is already inside of a shielded cavity, and is therefore as well protected as can be - why try to make things any better than they already are? Them's my feelings on ground loops inside of a guitar. Check with me tomorrow to see if I've changed my mine..... ya never know! ;D HTH sumgai
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Post by dd842 on Mar 23, 2007 13:11:09 GMT -5
..... If Dan gets any better at this, unk, Chris and I are gonna have to put our marbles back in the back and go home! ..... Thanks sumgai. I appreciate it, but it is funny you used the phrase "gift horse" in a different thread earlier today. ;D sumgai, I also have a question about this and I am especially interested because you don't subscribe to the method of running a wire from the back of each pot to a common lug/terminal attached to the shield. I have shielded only one guitar to date. I did not use star grounding, and I left the layout of the wiring pretty much as it was (except I used new wire and made sure any ground loops were eliminated). I will try to clearly describe what I did so that you can have a reasonable chance of understanding my ramblings. The guitar was a single humbucker with one volume and one tone pot - oh, and it did NOT have a pickguard. I made sure there was electrical contact between the pickups and the shielding, eliminated ground loops, and then attached the tremolo ground to one end of the 400 V capacitor and attached the other end of the 400 V capacitor to the hot lead of the output jack (which is also what the wire from the back of the volume pot was connected to). [glow=red,2,300]EDIT: regarding hot lead - DO NOT DO THIS![/glow] See sumgai's response below - Dan. I am now shielding my friend's strat. So my question is, if all I want is afford him some basic protection against shocks and the elimination of hum, is the following gonna work? 1) shield the pickup and control cavities 2) shield the pickguard 3) ensure they will make electrical contact with each other 4) ensure the pots, switches and pickups have electrical contact with the shielding 5) eliminate ground loops 6) run the tremolo ground to one end of the 400 V cap and the other end of the 400 V cap to the hot lead of the output jack [glow=red,2,300]EDIT: regarding hot lead - DO NOT DO THIS![/glow] See sumgai's response below - Dan. 7) ... and, of course, turn the volume up Thanks, Dan
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Post by sumgai on Mar 23, 2007 19:45:22 GMT -5
Dan, WHOA! STOP!!!!You did WHAT?You wanna repeat that?OK, that's it. Put your hands in your pockets, and back away from the workbench, right now!I might have let the first instance pass, thinking you just made a typo. But your second iteration isn't a mistake in typing, that's a gen-u-wine shortcoming in your electrical ed-ju-ma-cation. Short and sweet:The point of that 400 v, 0.33µf; cap is to isolate the guitar's ground from you, as you touch certain metallic items like f'r instance, the strings. So what's important to me right now is, just where did you "learn" that connecting the cap to the jack's hot lead is the proper method? Long and drawn out:What John Atchley is all up in arms about (and there's no conclusive proof that he's tilting at a windmill here) is the fact that under certain conditions, a particular kind of malfunction in a tube amp could lay the B+ High Voltage onto the ground circuit. The time it sits there may be short, but in a worse case scenario, that's exactly the time you'd be touching the strings, and touching something else at the same time, like a mic, or another player, or standing in a puddle of water at an outdoor festival, whatever....... The shock may be short, but it will definitely be no less sharp than any other kind of shock you could possibly receive in these conditions. John's recommendation for reducing that hazard down to non-life threatening levels is too cheap not to do it. Not only that, he also explains it pretty well on his site, and has some pretty good images to show what he's done, and how to do it. While I've been rather curt with you on this one, I'm sure you realize that what I'm really in tizzy about is safety, first, last, and foremost. You, my fine feathered friend, are on the way to becoming my dearly departed FFF, should you rely on that wiring for your health and safety any longer than it takes you to open your guitar and correct this mistake. Aside from all that, it seems to me that you were also introducing a path whereby your body's natural aerial tendencies were being sent directly to the output jack's hot lead...... didn't that kinda cause just a teensy bit of extra noise in your sound, every time you touched the strings? Inquiring minds wanna know. OK, diatribe over. The rest of your plan looks good to me. Just get past the above deficiency, and all will be well! ;D sumgai
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Post by dd842 on Mar 23, 2007 21:23:03 GMT -5
..... just where did you "learn" that connecting the cap to the jack's hot lead is the proper method? ..... John's recommendation for reducing that hazard down to non-life threatening levels is too cheap not to do it. Not only that, he also explains it pretty well on his site, and has some pretty good images to show what he's done, and how to do it. While I've been rather curt with you on this one, I'm sure you realize that what I'm really in tizzy about is safety, first, last, and foremost. You, my fine feathered friend, are on the way to becoming my dearly departed FFF ..... ..... your body's natural aerial tendencies were being sent directly to the output jack's hot lead...... didn't that kinda cause just a teensy bit of extra noise in your sound ..... THANK YOU! sumgai. “My friend” really is my friend on this one, and I’d prefer that my lack of knowledge not to send him to his grave. Truth be told, I don’t have the original guitar I was referring to anymore and I was trying my best to recall what it was I did. Incidentally, I had received instruction (from someone on this forum who I trust) and I was reasonably certain that I was correct in remembering what I actually did. Judging from your reaction, I obviously wasn't remembering it properly, so I dug up the schematic I used to illustrate my situation (it is not exact, but close - my guitar had only two wires from the pickup). The fact that I wrote hot lead in the first place does, as you say, certainly expose a gen-u-wine shortcoming in my electrical ed-ju-ma-cation, and I genuinely appreciate you making good and sure I know it. www.seymourduncan.com/support/schematics/schematicspdf/1hum_1vol_1tone.pdfI see that I incorrectly stated "hot lead" – it is in fact the sleeve (ground) that I attached the 400 V cap to. I have no idea if that still makes me an electronic boob in danger of electrocuting myself as I test this guitar ... well, I'm pretty sure about the electronic boob part. ;D There was absolutely no extra sound when I touched the strings – it was so quiet it was beautiful. sumgai, my sincere apologies for my error - I sure feel badly that I put you in the position that I did (alarming you, and wasting your time responding to my erroneous input). And my heartfelt thanks for your dramatic response. In case anyone reads my previous post isolation and is unfortunate to rely on it, I am going to go back and edit it by including next to it in glowing red “DO NOT DO THIS!”. Now that I have identified that it actually was going to the sleeve, is that going to work? Thanks ... I mean, really, thanks! Dan
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Post by sumgai on Mar 24, 2007 1:45:52 GMT -5
Dan, Ah, yes, I see it all now, it was a case of a self-compounding error. Happens all the time around here. We call it EOA...... Early Onset of Alzheimers. Yes, the sleeve of the jack is the ground that we all know and love, no question about that. If that's all there is to it, then we're golden, let's ship this bad boy outta here! Apology accepted, and editing is not a bad idea. Neither is attracting attention to possibly hazardous errors of this nature. It's a damned sight better to talk about it before hand, than the alternative, eh? Yours in jubblies, electronic or otherwise......... sumgai
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Post by dd842 on Mar 24, 2007 8:20:40 GMT -5
..... Yes, the sleeve of the jack is the ground that we all know and love, no question about that. If that's all there is to it, then we're golden, let's ship this bad boy outta here! Apology accepted, and editing is not a bad idea. Neither is attracting attention to possibly hazardous errors of this nature. It's a damned sight better to talk about it before hand, than the alternative, eh? Thanks again, sumgai. Your brilliant display of huge red text was more than a welcome sight to me ... sure as heck beat the thought of reading an obituary. All the best, Dan
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Post by ashcatlt on Mar 25, 2007 22:54:01 GMT -5
not to derail the thread, but this got me to thinking. Is there any reason that capacitor can't go just about anywhere in the ground path? -edit - As long as it's somewhere before the bridge/string/switch ground -edit- Like even outside the guitar somewhere.
In fact, won't the DC blocking caps in my pedals do about the same thing? I understand they won't be able to handle all the voltage, but that just means they burn up instead of me, right?
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Post by sumgai on Mar 26, 2007 4:07:50 GMT -5
ash, Valid questions are always welcome, no derail is possible under such circumstances. In point of fact, a capacitor is made of two conductors that have a known distance between them. That gap may be filled with air, or some material called a dialectric - usually somewhat electrically resistant, yet physically malleable. When a cap is forced into overdrive like you suggest, there are only two possibilities..... either it opens up completely, leaving no possible path for electricty to flow, or else it shorts completely, guaranteeing that the next person in line (that would be the party in the second part, namely, you), will now receive the full dump of voltage-on-steroids. What d'ya wanna bet that most caps don't open up when they go bad? Tha's right, they usually short out, sort of like the opposite of a fuse. Not always, but the question here is obvious: do you wanna play the odds on that? Best advice: don't trust under-rated parts to do the right thing when it comes to protecting your health or your life. In fact, don't trust any parts for that job! But then again, sometimes you have to compromise, I understand. Just don't do so in a foolhardy manner, that's all I ask of you. </lecture> sumgai
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Post by dd842 on Mar 26, 2007 13:26:17 GMT -5
Just wanted to let you know how the strat shielding ended up working out (the fact that I'm still here and able to post is a good sign!) I had never shielded a strat before - I'd only shielded one guitar with a humbucker - so the reduction in hum and noise was far more pronounced with the strat. For example: when I first tested the strat I could only stand turning the gain on the amp to about 3. Anything more and it became obnoxious and intrusive.
Now I can turn up the gain until it can't stand me - at about 9 it starts to feed back (as opposed to hum and hiss) ... and that is with the guitar about three feet from the amp. A couple of little things I did that I hadn't planned to:
1) I took the plastic cover off of each pickup, put a strip of shield over the electrical tape that actually wrapped the coil, and put the cover back on (I've heard of guys going full bore on this, shielding the top by using a one hole punch to make holes for the magnets to protrude through)
2) I adjusted the action so that the coils could sit lower in the pickguard, allowing more of the coil to be under the shield Anyway, what a capital c Cool modification - I think my friend will enjoy what amounts to, in essence, a whole other guitar. Dan
P.S. I was going to write a "brand new" guitar, but that's what created the need for shielding in the first place ;D
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Post by ashcatlt on Mar 26, 2007 14:17:26 GMT -5
Okay, i can dig that about the caps shorting on failure. But what about the other part of the question? Could you interrupt the ground somewhere before the guitar with that cap that's suggested in the QTB article and have the same effect? I'm thinking either a (plastic) barrel adapter, a plastic enclosure with in and out jacks, or even just a cable with a cap in it somewhere.
Would that have the same effect, and more importantly, would it affect the tone adversely?
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Post by sumgai on Mar 27, 2007 1:33:49 GMT -5
ash, I'm thinking that this question is also a good one, and perhaps it's worth wondering, why hasn't anyone asked this before. Obviously, most GuitarNutz just accept the layout as shown, and move on. The real techies among us know the reason already, so that leaves you, and a handful of others here that wanna know "why not".
Dan, DarKnight, anybody..... One of you guys wanna take a crack at this?
sumgai
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Post by dd842 on Mar 27, 2007 10:31:09 GMT -5
..... The real techies among us know the reason already, so that leaves you, and a handful of others here that wanna know "why not". Dan, DarKnight, anybody..... One of you guys wanna take a crack at this? sumgai I'll try, seeing as you have properly and implicitly set me up as NOT being a real techie. So READER BEWARE! In terms of tone, the cap in the guitar would not affect it much if it is wired along the lines of the QTB mod - although I think it would if you substituted and went to, say, .10µF or something. I understand the idea of the cap in the guitar to be that I would get enough of a jolt in my fingers to know something isn't right, but still hopefully have enough time to appropriately react to the situation (like maybe throw my guitar across the room or something because of, you know, an electrical problem ... not the sudden realization of my actual versus perceived skill level or anything). With what Ash is talking about - if you just hook up an external 400 V cap "plug-and-play" kind of thing - I wouldn't think that would affect the tone, but would you still achieve the same warning (i.e. does it matter if the cap in the guitar is isolated to the ground)? If that makes no difference - and all that matters, ultimately, is that the cap reduces the shock somewhere along the line before it gets to you, then I guess the cap in the external device is doing its' job and you would still have time to react. It sounds relatively easy to do, and I could see having one in case you happen to be using an unfamiliar guitar and amp in an unfamiliar place where you are not sure about the wiring. But, honestly, if it was my guitar I would just put the cap in the guitar ... we know that works. The odds of needing the cap in the guitar to do it's job are slim as it is, so - thankfully - you would be hard pressed to test it in real life situations. Personally, I wouldn't want to find out that my theory that the external method works is wrong if I had a good alternative - which I do. Since I've now used up my daily quota of making stuff up, that concludes my presentation. Thank you. Dan
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Post by ashcatlt on Mar 28, 2007 0:27:43 GMT -5
I was relatively used to the fact that if I touched my bass player, or didn't wear shoes in the basement while playing my guitar, that I was going to get a shock.
I remember another time I was playing a mustang through a vibroverb and singing into a shure green bullet plugged into an ampeg fliptop. I'd step up the mic and my fingers would tingle, my nose would hurt and the lights in the room seemed to flicker. Figured out a bit later it was actually my eyelids flickering.
I had the (non polarized, two prong) plugs to my tube amps (an Airline 1x12" and a Gibson Atlas built into a 1x15" combo) painted on one side. If you looked at a polarized outlet with the fat side on the left, the paint went up (most of the time).
I never thought I was close to death.
Gave the Atlas to a bassist friend of mine. His band practiced with a tube driven PA. I forgot to tell him about the paint on the plug. The had to unlpug the amp to get him to let go of the microphone. He's not dead, but he needed new shoes. That amp is at music - go - round now with a brand new (grounded) power cord. I think they want almost $300 for it.
Ah, good times.......:{
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Post by dd842 on Mar 28, 2007 8:14:22 GMT -5
..... I'd step up the mic and my fingers would tingle, my nose would hurt and the lights in the room seemed to flicker. Figured out a bit later it was actually my eyelids flickering. ..... Gave the Atlas to a bassist friend of mine. His band practiced with a tube driven PA. I forgot to tell him about the paint on the plug. The had to unlpug the amp to get him to let go of the microphone. He's not dead, but he needed new shoes. LOL (sorta, you know what I mean ) You are reminding me of part of pmcook's first post - it was smokin' ;D ..... In the mean time, All this " Killer hot wire " had me thinking about the old cigarette stuck on the head stock trick, Flip a switch and the bass string turns [glow=red,2,300]Glowing Red Hot [/glow]so you can light your Cig. the same way a cig car lighter works.... Now that would just blow Jimmys lighter fluid "Burning Guitar " right out of the water .... By the way, I was thinking more about your question about tone: The way I wired the cap into the strat is that it is attached to the tremolo ground wire ... it is directly attached to neither the volume nor the tone pots. I am not sure if that has anything to do with why tone is unaffected, or if it's simply that the cap value won't affect tone. But if avoiding those pots is a big part of the equation, then I don't see how an external method could avoid affecting the tone. Dan
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Post by sumgai on Mar 28, 2007 10:06:54 GMT -5
Dan,
Yer gettin' purty close there, pardner!
sumgai
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Post by dd842 on Mar 28, 2007 12:55:00 GMT -5
Dan, Yer gettin' purty close there, pardner! sumgai Hmmm... INITIALLY, I wrote: Initially, my question was about shock hazard and isolating the cap to ground. I also suggested that tone may be unaffected. No response from sumgai ... THEN, I wrote: When I suggested that there could be a tone issue, and sumgai said I was getting close ... ..... I am reasonably certain that if ash was going to electrocute himself, there would have been big red warnings to put his hands in his pockets, so I am detecting that it is a tone issue. "When capacitors are connected in series, the total capacitance is less than any one of the series capacitors' individual capacitances. If two or more capacitors are connected in series, the overall effect is that of a single (equivalent) capacitor having the sum total of the plate spacings of the individual capacitors. As we've just seen, an increase in plate spacing, with all other factors unchanged, results in decreased capacitance." (source: www.allaboutcircuits.com/vol_1/chpt_13/4.html ) So, I am suggesting that where the external device cannot avoid the pots, and therefore the cap on the tone pot (i.e. as in standard strat wiring), the two capacitors end up in series, diminishing capacitance, and would let too much high tone into the mix - so the tone would be very bright? Is a gittin' purtier or uglier there, Billy-Joe-Bob? Dan
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Post by ashcatlt on Mar 28, 2007 13:20:03 GMT -5
Actually, now that i think of it, that entire last post probably has more to do with differences in AC ground potential than any unexpected DC laying across the amp input. Seems the cap may not have helped in these instances. Though mathematically it seems like a difference in AC ground potential would look like a DC offset of one of the signals, I don't think it actually works that way.
i think the basic idea is that having the cap on the "signal" side can't help but affect the tone. I'm not sure doing it as I described would put the DC blocking cap in series with the tone cap though.
The blocking cap is in series with the pickups. Tone cap is parallel to the pups. Therefore the blocking cap must be parallel to the tone cap.
What’s confusing me is that we do so many horrible things to ground in guitar wiring as it is. It’s where we dump all our noise, dump the treble we don’t want (by way of the tone cap) and all the rest, so how come a cap on the ground side of things will affect the tone of the circuit? I understand that in AC signals (like a guitar makes) the electrons have to go back and forth, but…
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Post by dd842 on Mar 28, 2007 13:29:25 GMT -5
The blocking cap is in series with the pickups. Tone cap is parallel to the pups. Therefore the blocking cap must be parallel to the tone cap. If that's the case, I wonder if it might create another problem: increased capacitance with darker tone (that's assuming I am understanding this properly - which I may not be). Even if the external method works through trial and error, it sounds like it will work only for the guitar you ended up dialing it into. A different guitar - e.g. you say pickup s, what about a guitar with a single pickup, or a different pot resistance, or a different tone cap value - is that going to sound the same? Dan
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Post by dd842 on Mar 28, 2007 15:14:13 GMT -5
This all raises another question ...
Many of us have trouble finding .33µF 400v metal film caps, but I believe they can be sustituted with .22µF or .47µF.
I don't know if it's any easier to find caps with higher µF and lower v, but if it is, could we put two caps inside the guitar, in series and achieve the same result?
For instance, all I could find one time was a .47µF 250v cap. If two of those in series would have given me a .235µF 500v, then - tone and shock protection both considered - would I have been better off using one or two? ... which would have been "closer" to a .33µF 400v cap?
Dan
P.S. The .47µF 250v cap was pretty big, so I don't know if there is actually enough room for multiple caps in there anyway. I'm just asking.
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benjy304
Apprentice Shielder
Posts: 29
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Post by benjy304 on Mar 28, 2007 20:07:28 GMT -5
A while ago I disassembled a broken CRT computer monitor and found quite a few high-voltage capacitors, both electrolytic and mylar, in there. If you've got somewhere you can get ahold of one of these (and can avoid imploding the picture tube ;D) you can find all kinds of goodies. And making the picture tube safe to handle is as easy as removing the high-voltage lead to the CRT from the flyback transformer and poking a hole in the area covered by the little connector thing with an ice pick or awl or whathaveyou to break the vacuum.
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Post by sumgai on Mar 28, 2007 21:09:11 GMT -5
benjy, I wanna see that in action, please!
But first, let me purchase this life insurance policy on you.......
My take on this: Don't do it. The risk is too high of not surviving the experience.
Since we don't normally play with picture tubes here on the GuitarNutz2 forums, I'll not trot out the bold, oversized, red letter warning signs. I think everyone here knows how I feel about safety being first, so this "regular" post should be enough.
sumgai
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Post by ashcatlt on Mar 28, 2007 22:33:51 GMT -5
This all raises another question ... Many of us have trouble finding .33µF 400v metal film caps, but I believe they can be sustituted with .22µF or .47µF. I don't know if it's any easier to find caps with higher µF and lower v, but if it is, could we put two caps inside the guitar, in series and achieve the same result? For instance, all I could find one time was a .47µF 250v cap. If two of those in series would have given me a .235µF 500v, then - tone and shock protection both considered - would I have been better off using one or two? ... which would have been "closer" to a .33µF 400v cap? Dan P.S. The .47µF 250v cap was pretty big, so I don't know if there is actually enough room for multiple caps in there anyway. I'm just asking. I'm pretty sure that ain't gonna work as stated. seems to me like you'd have .235uF until the first cap shorted because you exceeded 250V, then you'd have .47 till that one shorted. then you'd have 0.
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Post by ashcatlt on Mar 28, 2007 22:46:55 GMT -5
btw - i think my way creates a bandpass filter. The blocking cap + impedance of the pickups create a highpass filter, and the tone cap + pot create a high pass filter, allowing only the mid freqs through.
I also think I've figured out the answer to my other question so for no good reason I'll try to flesh it out using a reference from my trucking days.
If you want to go from chattanooga to atlanta and back (without stopping in atlanta), you could take I-75S till you reach the I285 loop, then go around the loop and back onto I-75N. The treble and noise would like to get from atlanta to chattanooga, so they get on the I285 loop, but they keep missing the exit for I75, and keep going around the loop...
that makes sense to me anyway.
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Post by dd842 on Mar 29, 2007 14:57:29 GMT -5
ash, I don't really get the AC / DC stuff you are mentioning (it's the large DC shock from a vintage amp I am concerned with - the cap doesn't actually provide much protection from improperly wired dwellings, at least that is my understanding). In terms of tone alteration, whether the caps are in series or in parallel, between the two of us, I think it's a given. You thought putting two higher uF lower v caps in series would provide less voltage protection, but I had read that caps are sometimes used in series where a higher working voltage load is required (which is not to say that it's true - just that I read it ... so I don't know). You talk about bandpass filters and tone caps and blocking caps ... and chattanooga ... as for me, I am open to the possibility that you may be a genius, 'cause I don't know what you're talking about once we hit Chattanooga ... LOL ... but I don't understand me anymore either ... LOL And I have seriously gone at least as far as I should with my electrical theories, lest anyone rely on them. Dan
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Post by sumgai on Apr 4, 2007 2:21:33 GMT -5
Time to finish this off.......... The nuts and bolts of it is, if you insert a capacitor into a circuit, in series with the signal, then you modify that signal, there's no getting around that. Electrically speaking, you introduce a phase shift between the voltage and current. In turn, that phase shift is sensitive to frequency (we've already been over this, right?), and at that point, you're talking about the tone. Now, while it seems obvious, the fact is, most of us tend to forget that the ground portion of a circuit is still a portion of the circuit - it carrys the signal too! The effect of a capacitor will occur no matter where in the circuit you position it, inluding that part of the circuit labeled as "ground". Mr. Murphy personally guarantees that the effect will not be to your liking. HTH sumgai
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Post by dd842 on Apr 4, 2007 9:50:50 GMT -5
..... The nuts and bolts of it is, if you insert a capacitor into a circuit, in series with the signal, then you modify that signal, there's no getting around that. ..... Now, while it seems obvious, the fact is, most of us tend to forget that the ground portion of a circuit is still a portion of the circuit - it carrys the signal too! The effect of a capacitor will occur no matter where in the circuit you position it, inluding that part of the circuit labeled as "ground"...... HTH sumgai kinda helps ... I mean, yes, absolutely it helps ... but, sensei, I have a couple of questions If the tone capacitor is going to affect the signal (tone), then I postulate the tone would be most adversely affected by adding the .33uf 400v capacitor either in series with or parallel to the tone capacitor. Is that correct? You say the ground portion of a circuit is still part of the circuit, and carries the signal too. But in order for tone to be least affected by the second capacitor, then having the cap attached to ground must be the one path where you can add a capacitor without creating either a capacitor in series or a capacitor in parallel to the tone capacitor (otherwise wouldn't tone would be affected?) ... is that correct? Sorry for the question - I know you wanted to finish it off ... but I want to make sure I understand ... Am I gettin' it right , or am I in my own little world ? Thanks, Dan
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Post by sumgai on Apr 4, 2007 11:25:25 GMT -5
Dan, Yes, you have it right. You've wandered a bit...... not too far, but a bit. Recall that the very term 'ground' come to us from the first days of radio. It meant, more or less, the solid part of the circuit that carried the radio waves. That's as opposed to the very air itself being the remaining component in the circuit to carry radio waves. And from that, you should deduce that since we're trying to get rid of a radio interference (the hum we find so objectionable), we need only to knock out one side of the circuit, right? Well, it's kinda hard to attach a capacitor to the air, but it's very easy to attach it to the solid ground, eh? So, the .33µf cap is actually in series between ground and the strings, which are in series with our bodies, which is in series with, and acting as an antenna for, the air that's carrying the radio waves that we call interference (when we're in polite company). Notice that at no time was any signal from the pickup(s) part of that radio circuit. Ergo, the tone is unaffected. Voila! No, I wasn't putting paid to the account, I was only answering the question that started the whole topic. I simply wanted to let you and others think their way through the problem first, instead of just blurting out the answer right away. Where's the fun in denying you the opportunity to think for yourself, eh? ;D And if nothing else, the whole forum exists for one reason only, and that's to make sure that you are at your comfort level of understanding. Of course, if you like your own little world better......... ;D ;D sumgai
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Post by dd842 on Apr 4, 2007 12:09:49 GMT -5
..... And from that, you should deduce that since we're trying to get rid of a radio interference (the hum we find so objectionable), we need only to knock out one side of the circuit, right? Well, it's kinda hard to attach a capacitor to the air, but it's very easy to attach it to the solid ground, eh? So, the .33µf cap is actually in series between ground and the strings, which are in series with our bodies, which is in series with, and acting as an antenna for, the air that's carrying the radio waves that we call interference (when we're in polite company). Ah, yes. So undesireable interference gets blocked (without creating series or parallel caps - I know you said it's all part of the same circuit, but I am still guessing that avoiding series or parallel is desireable to avoid affecting tone ... or are those differences such that, in terms of tone, they don't even matter?) and, conveniently, it also affords us the opportunity to have our bodies protected from a potential DC shock coming back through the same circuit from the amp. Right? It is fun for us too. Especially if we are not left to rely on our own (sometimes incorrect) conclusions, of course. So thanks for picking this up again. Good God, no! ;D As Carla Tortelli once said, "Last one in the pool is a Clavin" ... to which Cliff replies as he runs as fast as he can "Oh, no, I'm not gonna be a Clavin!" Dan P.S. Out of curiosity from a previous question, can two .67uF 200v caps be combined in series to effectively have one .33uF 400v cap ... i.e. do you get a 400v working load, or a 200v working load?
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