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Post by lordquilton on Nov 23, 2015 22:45:39 GMT -5
I'm getting ready to install treble bleeds on my jap Les Paul, and I came across a Youtube video for the Fender Tone Saver. What got my curiosity going was that it is apparently "directional", meaning one end of the device has a blue stripe to indicate it is to be connected to the input lug of the pot. "Maybe I've been doing it wrong" I thought. I dug a little further and apparently Fender claims it is "more than just a treble bleed circuit".
So I guess my reason for starting this thread is two-fold. 1) DOES it matter which end is which for the components in a simple high pass filter network?(I think I know the answer)
2)What sort of mysterious component would make this Fender Tone Saver directional (and so hideously expensive)? Presumably it's an inductor, but is that actually going to make a difference here?
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Post by JohnH on Nov 24, 2015 1:50:03 GMT -5
Im calling it BS
For three reasons:
First, there is no known useful passive component that is directional and could help in this situation. Certainly wouldn't want to see (or hear) a diode there.
Second, even if there was a directional component in the system, the guitar signal is pure a/c. It goes up and down, plus and minus, relative to a ground reference. So it couldn't make any difference which way round you connected it.
Third, simple resistor/capacitor treble bleed networks work very well if you pick the right values. Much better than nothing (which is usually what is on offer in a stock guitar) and also better than just a cap alone.
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Post by newey on Nov 24, 2015 6:14:57 GMT -5
Yeah, when I read this I thought they must have sourced electrolytic caps. Directionality wouldn't matter in this application, as John notes, but some guy writing the directions saw that the cap had a positive side and decided it must mean something . . .
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Post by ashcatlt on Nov 24, 2015 13:34:57 GMT -5
When I read the OP I was thinking there might be some combination of series and parallel components where order could matter. I can't see any way that it possibly could with only two terminals like this, though.
Likewise, I'm pretty sure there's no inductor in there because in series with the signal like this it would just make things worse.
It made me think, though. Shortly after I started hanging around here I asked the question whether a passive V pot in a stompbox would cause the same treble loss as the one in the guitar. I was told (don't remember by whom, and I'm not searching for it) that it would be the same thing because AC goes both ways and whatnot. It occurs to me just now that this is wrong.
Anyway, I find it amusing when this is called treble bleed, when it is in fact actually shelving bass cut. Do other people actually hear this as staying flat as you turn down the pot? I always hear it thin out, like a variable strangle switch. I have been known to use that aspect for special effects in the past, but it weirds me out that so many people act like nothing's happening.
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Post by sumgai on Nov 24, 2015 14:01:34 GMT -5
Weeeeeellllllllllllllll, First, the two YouTube videos that I reviewed (out of several dozen possible Google results) take pains to make it known that this is a combinaiton of a resistor and a capacitor rolled into a single casing. That means only two leads to solder, instead of four, which means a simpler and quicker installation. Less chance for a non-professional to botch things up, that's how I read it. From what I saw, I'm not so sure that we're dealing with an electrolytic cap here. More on that in a moment. I have the strange feeling that Fender has once again succumbed to the Magic of FelderGarb, ala their (in)famous GreaseBucket mod. (Is it a mod if the factory does it before it even goes out the door?*) I think that we've just seen the ultimate dumbed-down instruction set: "Look, this goes here, and that goes there, Presto - you're done. What's to worry?" I'm sure that any Nut who's been here more than a month can recall at least one posting from a newcomer that asked "which way do I hook this up?", yes? Well, Fender is merely trying to reduce their support costs (phone calls, email, etc.) by publishing a video that shows exactly how to do it. From their standpoint, this is good business, and I suppose I can't argue with that factor. But in so doing, MarketingSpeak crept into the equation, and that is what we Nutz are taking issue with. Suffice it to say, someone is gonna get it backwards, on purpose or otherwise, and no one is gonna be able to tell the difference. By their own admittance, it's a cap-and-resistor combo, and it hooks up to the same points (in a guitar circuit) as any other treble-bleed design. Ergo, if it quacks like a duck, blah blah, woof woof.... More power to them, if they can make their money back on this one. Now, about that electrolytic cap thing. In point of fact, there is a reason to mark the polarity on them, and an equally good reason to obey that marking when using them, but I can't say it any better than this link here, found at Wikipedia: en.wikipedia.org/wiki/Electrolytic_capacitorProbably more than you wanted to know, but it's nice to see that sometimes things do happen for a reason, be it common sense or arcane. The first few paragraphs are all that are really needed here to clear up any apprehensions. And LQ, you've been doing it right all along. IOW, don't step in the huzzah! HTH sumgai * As an old (mighty old!) hot rodder from the days of carburetors and Kettering ignition, I can personally tell you that no car ever came out of Detroit without first incorporating "mods" originally performed by hot rodders. Dual carbs? Check. Dual exhaust? Check. Hydraulic brakes? Check. Transistor ignition? Check. The list goes on, for volumes' worth of pages. But it's not important to be that old to remember these thing personally, it's only important to remember who actually figured out the way to do it, and then remember that he (or she) got run over by The Big Guns in the business. The highway to success is littered with forgotton, unsung heroes who had the temerity to do it differently than what was dictated by The Big Boys... not to mention that they did it better, too. Wanna guess what The NutzHouse is full of?
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Post by JohnH on Nov 24, 2015 14:27:02 GMT -5
Anyway, I find it amusing when this is called treble bleed, when it is in fact actually shelving bass cut. Do other people actually hear this as staying flat as you turn down the pot? I always hear it thin out, like a variable strangle switch. I have been known to use that aspect for special effects in the past, but it weirds me out that so many people act like nothing's happening. Within reasonable limits, and if you pick the right resistor and cap, then it does indeed stay reasonably flat in terms of tonal balance. The key is the extra resistor. Its not perfect though, and keeping the tone consistent in the volume range 4 to 10 on the volume pot means that it will start to drift away a little in the low range 1 to 4. Or you can optimise for the low range and get a little treble loss in the high range of volume. As an example, my basic LP/Humbucker recipe for 500k pots is a 1nF in parallel with 150k. With that, I can get all the frequencies up to 3500hz (where it rolls off anyway) to remain consistent relative to each other within about +/-1.5db, between about 3 to 10 volume, which sounds OK to my ears.
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Post by reTrEaD on Nov 25, 2015 10:48:37 GMT -5
So I guess my reason for starting this thread is two-fold. 1) DOES it matter which end is which for the components in a simple high pass filter network?(I think I know the answer) The only meaning of the stripe is to indicate which end the "outer" foil of the capacitor is connected. In the case of a simple low-pass filter, connecting the outer foil of the capacitor to ground would result in microscopically less noise, since the outer foil acts as a shield. Realistically, it makes little difference even in that configuration. 2)What sort of mysterious component would make this Fender Tone Saver directional (and so hideously expensive)? Presumably it's an inductor, but is that actually going to make a difference here? No inductor involved here. The Fender Tone Saver is just a second-order treble bleed. A resistor in parallel with a capacitor. It's expensive because it has the Fender logo printed on it.
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Post by sumgai on Nov 25, 2015 12:46:25 GMT -5
... It's expensive because it has the Fender logo printed on it. Leave it to reTrEaD to reduce my four paragraphs of technobabble to one sentence! Obviously I didn't say it better.
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Post by ashcatlt on Nov 25, 2015 12:58:25 GMT -5
JohnH - I've heard you say that, and seen it on GuitarFreak and such... Maybe my experience has always been with the wrong C and/or R for the guitar, but I'm pretty sure they were all factory installed. Maybe I just turned it down to far - going for extremes as usual.
I can't really see how the R does anything but change the taper of thing. Maybe it changes the taper of the cutoff frequency differently from the low shelf level, but IDK. I'm just not able to visualize how it really does what you say it does.
reTrEaD - Second order?
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Post by JohnH on Nov 25, 2015 15:27:15 GMT -5
JohnH - I've heard you say that, and seen it on GuitarFreak and such... Maybe my experience has always been with the wrong C and/or R for the guitar, but I'm pretty sure they were all factory installed. Maybe I just turned it down to far - going for extremes as usual. I can't really see how the R does anything but change the taper of thing. Maybe it changes the taper of the cutoff frequency differently from the low shelf level, but IDK. I'm just not able to visualize how it really does what you say it does. reTrEaD - Second order? I think controlling the cut off frequency at the low frequency side of the treble peak is what the resistor does. The cap starts to feed through significant extra treble at frequencies above where its impedance matches the resistance of the upper branch of the volume pot. This starts at a high frequency when volume is high, and maybe just the right amount is fed through. But at lower volume, the upper part of the pot is high resistance and boosted treble begins at much lower frequencies, rising up to a relatively much higher and excessive peak, with a thin tone as a result. The extra resistor in parallel with the upper pot branch keeps the resulting combined resistance from getting so low. Eg at 5 with a 500k log pot and 150k resistor, the upper branch is 112k instead of about 450k. This means a 1nF cap starts to raise treble from about 1400hz, instead if about 350 hz. It does change the pot taper. In this case, a 10% taper now functions more like about a 30% taper, which I find is just about right.
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Post by sumgai on Nov 25, 2015 15:37:13 GMT -5
ash, I can't really see how the R does anything but change the taper of thing. If it were merely a matter of that resistor changing the pot's taper, then it logically follows that the resistor would have no effect on the cap's ability to affect the tone, right? Yet it's universally accepted that installing a resistor (preferably near a correct value, to be determined empirically) has a profound effect on the tone, during the pot's rotation. This is because the resistor is holding the capcitor's discharge rate at a near constant. Yes, it's in parallel with the "upper" leg of the voltage divider, but until that leg nears the value of the resistor itself, the overall resistance seen by the cap does not vary to a audibly noticible degree. If you left out the resistor, the discharge rate would be at the mercy of the voltage divider's upper leg, and that substantially affects the overall tone of the axe, usually detrimentally. For more on this, search for capacitor, charge rate, and time constant. HTH sumgai * Since you asked him directly, I'll let reTrEaD answer your question about filter orders.
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Post by ashcatlt on Nov 25, 2015 17:55:05 GMT -5
This is because the resistor is holding the capcitor's discharge rate at a near constant. Yes, it's in parallel with the "upper" leg of the voltage divider, but until that leg nears the value of the resistor itself, the overall resistance seen by the cap does not vary to a audibly noticible degree. If you left out the resistor, the discharge rate would be at the mercy of the voltage divider's upper leg, and that substantially affects the overall tone of the axe, usually detrimentally. Ummm... All three components (C, R, top of V) are in parallel, no? All that the C cares about as far as charge/discharge is the parallel total of R and V. Well, actually it's the parallel total of the R and the top of V and the bottom of V and whatever other load is hanging off the end... The point being that still all that resistor really does is limit how big that top part of the V pot looks as you turn it down, and also kind of slows down how big it gets as it does get big. The R will have less impact on the total at higher pot settings. It changes the taper of the pot, kind of period. What we're looking at here is pretty much this: The Rs change with the rotation of the pot, and of course the source and load make some impact (especially since they are both reactive), but...
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Post by reTrEaD on Nov 25, 2015 21:14:20 GMT -5
Perhaps a bit of a wonky term. Second order or second approximation. What I meant by that is it's more than just the cap-only version. The whole point of "treble bleed" is to compensate for cable capacitance. But the effective of cable capacitance changes dramatically due to how much series resistance and how much resistance the pot puts in parallel with the cable as the volume control is turned. I can't really see how the R does anything but change the taper of thing. To be sure it does affect the taper in a rather pronounced way. But more importantly it also mitigates the effectiveness of the cap at highly reduced volume. Without the extra resistor, the cap-only version overcompensates severely at low volume settings. With the resistor, the compensation is slightly less than optimum when the volume reduction is slight but is still "close enough". This allows for a greater range of volume reduction before it gets too bright at the lowest settings. If I recall correctly, folks around here (led by John) were modeling these things with some simulation software before John's GuitarFreak. Even with the resistor in parallel with the TB cap, it does overcompensate at severely low settings. But not as much as it would without the resistor.
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Post by ashcatlt on Nov 25, 2015 21:41:25 GMT -5
Perhaps a bit of a wonky term. Second order or second approximation. What I meant by that is it's more than just the cap-only version. "Second-order" is a pretty specific term, basically meaning twice the rolloff of a standard first-order filter. I thought you might be seeing something I wasn't seeing... That's still just about the taper of the top of the V pot, and perhaps it's relationship to the taper of the bottom of the V pot, which is not actually impacted by the added parallel R. So, like, the top gets larger more slowly than the bottom gets small, which I guess would be different from just using a smaller pot or one with a different taper.
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