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  #16  
Old 03-19-2012, 09:10 PM
SteveO SteveO is offline
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Quote:
Originally Posted by fumbler View Post
Wow, that's a heck of a circuit for a passive guitar. 3 different value pots to go with the 4 caps. I'll bet that "Leo" guy might have been pretty good at designing amps if he had ever tried.
He couldn't play the guitar to save his life, though. He should have spent more time practicing and less time tweaking amps.
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  #17  
Old 03-20-2012, 08:02 AM
engiblogger engiblogger is offline
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Quote:
Originally Posted by NoahL View Post
What is the purpose of C3 in this setup? It's in a G&L S-500, with the treble AND bass rolloffs.

http://img.photobucket.com/albums/v2...0Schematic.jpg
could be used to ground unwanted harmonics as a switch debouncer

EDIT:
Strat pickups usually have a DC resistance of about 7k. a simple low pass RC filter with 7kOhms and .001uF has a -3dB rolloff of about 23kHz.
This takes away harmonics that are well beyond the range of human hearing. This could serve to mitigate feedback problems common in single coil pickups and lower the noise floor of your signal. All good things in my books!
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Never, ever ask your elderly, faithful hound to wire up patch leads....
cos you can't teach an old dog neutriks......

Last edited by engiblogger; 03-20-2012 at 08:10 AM. Reason: did some calculations
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  #18  
Old 03-20-2012, 08:43 AM
Sensible Musician Sensible Musician is offline
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This is what a circuit looks like when you tune it to the guitar. You end up with little fixes that shift it to where you want it to sound. Most of us do this by endlessly swapping pickups while leaving untouched all the components it makes more sense to change.

Some of my guitars have trimpots to level out relative volume between switch positions, or the relative effect of the tone control, or both. Some use the exact trick shown in this schemo. I like to tune literally each guitar this way; easiest way is to run my switch (or pickup) leads out and breadboard my controls in an outboard box - or at least as a web of test leads on my bench.

Someday I will properly study electronics and learn every trick with passive filters. But until then I've learned a lot of the tricks from just looking at schemos like this and asking questions like the OP is doing. Over time I've built up a bag of tricks that can solve most problems.

C3 in OP's schemo lowers the peak of the overall circuit. Similar value and effect of the resonance switch on Seymour Duncan Pickup Booster in position 1. Similar value and effect of a long cable.

Cap codes: it's easier for me to think of two digits as the number of Picofarads and the number as the number of moves in decimal places. So 101 is one decimal place move (the last digit is 1) and 10 (first two digits) is the value. So it's ten with one decimal move, or 100pF. Every multiple of 3 is a new unit: 103 is 10nF, (nanofarads) and 106 is ten microfarads. BTW it is much easier to read schemos using the correct units. E.g. if you need a 30pF cap in a Rat, instead of wearing the point off a pencil writing all those zeros, just write, "30pF." The 1kV is the voltage that a cap is rated for. Common practice is to use a cap rated for 2x the voltage your circuit is designed for - not an issue inside guitars. There should be one more marking on most caps - the tolerance. These are coded C though (?) - they go in order from very precise to very inexpensive. E.g. J is 5% and K is 10%.
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  #19  
Old 03-20-2012, 08:57 AM
engiblogger engiblogger is offline
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Speaking from an electronics technologist's POV, This circuit looks to be really nice.
as I said before, C3 takes away frequencies greater than the ear can hear. (noise reduction)
C1&4 are for low pass and hi pass filters for tone control
C2 will help take away VR2's scratchiness

If you are really not sure whether you want to populate them or not, drill a hole on your pick guard for a SPST switch (on off switch) and wire it in series with C3 . you can do the same for C2 if you want. now you can select whether you want that cap in the circuit or not while you are playing.

EDIT:
As a very simplified rule of thumb. Caps want AC to pass through them and they stop DC from passing through them. the bigger the cap, the lower the AC frequency they will allow. Its a little more complicated than that but in good audio circuits, you generally like to see a lot of filter caps. they take away noise. the reason why you don't see them that often is because they are expensive for guitar makers
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Originally Posted by jakey View Post
Never, ever ask your elderly, faithful hound to wire up patch leads....
cos you can't teach an old dog neutriks......
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  #20  
Old 03-20-2012, 09:08 AM
engiblogger engiblogger is offline
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Quote:
Originally Posted by walterw View Post
as mud
to clarify, flux capacitors are only used in time travel
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Quote:
Originally Posted by jakey View Post
Never, ever ask your elderly, faithful hound to wire up patch leads....
cos you can't teach an old dog neutriks......
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  #21  
Old 03-20-2012, 07:41 PM
walterw walterw is offline
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that's what i thought

also, a .001μF cap across hot and ground will quite audibly affect the treble.
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  #22  
Old 03-21-2012, 07:34 AM
fumbler fumbler is offline
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Quote:
Originally Posted by bagpipe View Post
Capacitor 3 is not a lateral flux-capacitor but a lateral-flux capacitor; that is, lateral modifies flux, and lateral flux is attributive, rather than flux capacitor compound and lateral modifying capacitor. Flux is commonly used in electronics and electromagnetic theory and application, but rarely in the context of a capacitor. In general terms, flux simply means the rate at which some quantity (such as electric charge or magnetic field) changes through a conductor (e.g. charge flux).

While they are not generally called flux capacitors, the common inductor is an electrical component whose function in many contexts could be thought of as a flux capacitor - it consists of a coil of wire that converts and stores electrical energy as a magnetic field where it can be retrieved when the magnetic lines of flux collapse.

Clear?
Absolutely clear.

Here's a schematic, if anyone needs one:


But how do I route my guitar to fit one? They're big.
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