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Thread: Wiring options, treble bleed?

  1. #1
    Senior Member LJD's Avatar
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    Wiring options, treble bleed?

    I have a HBII with 53/10 pickups and it's currently wired to the "pre 2007" specs. I am curious about wiring it differently to get the most out of the 53/10's. Since the ME Quatros came stock with 53/10 pickups I've considered trying that schematic . I've played ME4s and noticed how clear (amazing) they sound. It appears to be a sort of "50's wiring" setup with a treble bleed on the volume pot.
    I'm still not exactly sure what a treble bleed does when the volume is on 10 (highest, wide open). Does it make a difference? Will I get more clarity/air out of the 53/10s with a 50s style setup? Would changing the capacitor value from .033 to .022 help?

    schematics:
    Pre 2007 HBII: http://www.prsguitars.com/csc/schema...hollowbody.pdf (I removed the piezo system).

    ME4: http://www.prsguitars.com/csc/schema...uatro_2012.pdf
    Last edited by LJD; 02-18-2014 at 03:28 PM.

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    Senior Member garrett's Avatar
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    The treble bleed (actually treble bypass is a more accurate term) has no effect with the volume at 10. It's only engaged when you turn the knob down.

    The "50's style" wiring negates the purpose of the treble bypass circuit by connecting the tone control straight to the output instead of going through the volume control first. It retains the clarity as you turn down the volume, but the tone pot works differently. It won't have much effect in the top third or so of rotation. It's a personal preference thing between this method and the treble bypass.

    Changing from the .033 to a .022 uf cap will raise the resonant peak, which in other words means the frequency cut-off will be higher, so the tone won't be as dark when the knob is turned all the way down.
    --Garrett--

  3. #3
    Senior Member garrett's Avatar
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    You can try 50's style wiring by removing the treble bypass cap and connecting the tone control to the middle lug of the volume pot.
    --Garrett--

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    Junior Member Felix's Avatar
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    Quote Originally Posted by garrett View Post
    You can try 50's style wiring by removing the treble bypass cap and connecting the tone control to the middle lug of the volume pot.
    I've puzzled over how to do this with a circuit board in the middle, so to speak, and the answer seems to be to connect the right lug of the tone pot to the middle lug of the volume pot (through the tone cap), but doesn't the wire from the switch need to be soldered to the left lug of the tone pot? (On applicable PRS models the lug of the tone pot which is grounded by soldering it to the pot case has a wire running from it to the grounded lug of the volume pot, as well.) I've looked at how the P22 is and the Hollowbody (I) was wired, post-2007, and the way I've described seems to PRS' own method of wiring a piezo-equipped guitar with "'50s wiring". Do I have this right?

    Also, are there any comments from Hollowbody (I) owners whose machines are wired the post-2007 way? How does the wiring work for you? -And how would you compare it to a Hollowbody II (which is wired the pre-2007 way), if you have had the opportunity to compare?

    My CE-22 has the post-2007 wiring and is very bright. I love the tones I can get out of it, but the controls, EQ, and tone stacks have to be set up especially for it just because of the guitar's searing brightness. Also the "lowest point" in the tone control at just above 2 when the volume is full on; if the volume is lowered this region of lowest treble pass changes to a more normal slope -the darkest tone at zero, down from around 2- and the tone control works more as one would expect a tone control to work. The guitar also has a treble bleed cap, which seems totally unnecessary for a bolt-on, maple-necked guitar wired "'50s style", but I am sure there is some reason it is there, even if I don't understand it. I would like to tame the treble a bit. I use one long, high-capacitance cable and it helps, but only so much. (I have seen a man whom I consider to be a master of tone use two 18-foot cables mated together to increase capacitance in the circuit to tame the treble of his 50s-wired '57 Les Paul Gold Top; it seems to work very well for him!)

    Oh, and LJD? your Hollowbody II with 53/10s sounds like it is a dream guitar (and I'm jealous of those pups!). '50s wiring would just make it perfect IMO. BTW, I like the .033uf cap in my Hollowbody II very much. It has 57/08TMs and those are amazing pickups, so I shouldn't be so jealous. -I still am, but there you go....
    Last edited by Felix; 02-19-2014 at 05:51 AM.

  5. #5
    Senior Member garrett's Avatar
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    The one under "Current" here has the 50's style connection with the tone pot and the piezo:

    http://www.prsguitars.com/csc/schema...wbodypiezo.pdf

    Using crazy lengths of cable sure is a difficult (and expensive!) way to tame a guitar's high end. You can add capacitance by using a capacitor (imagine that!) that costs less than $1. Adding capacitance really just shifts the focus away from the highs and more to the mids.

    Cheapest way to cut the high end off that CE is to wire a resistor across the left and center lugs of the volume control. 470k Ohm is a common value and would drop resistance to about 240k, so that's like switching to a 250k volume pot. 1M Ohm is also common and would split the difference at about 333k. The higher the value resistor, the less treble you'll cut. You can calculate it here: http://www.sengpielaudio.com/calculator-paralresist.htm
    --Garrett--

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    Junior Member Felix's Avatar
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    Thanks, Garret, but won't using a resistor to lower the value of the volume pot's resistance simultaneously change its taper? -I'd rather change out the pot if I want a different value pot. As far as your suggestion of wiring in a capacitor (flip tone aside), good suggestion. I'd rather put in a better quality cap than the dollar cap you suggest; it (my CE-22) has a 180 pf round tan ceramic treble bleed cap and I don't even like seeing it in there, where a Mallory or Orange Drop or PIO should go - or no cap at all, perhaps. I still do not understand why that guitar has a treble bleed cap in the first place, '50s wiring having a reputation, along with maple, bolt on necks -which this guitar also sports- for producing a bright guitar, but I suppose PRS has their reasons for including it.

    Garret, I think that the PDF file you referenced is the wiring I described; so that's a yes on moving the wiring? -The pot grounding and all?

    Oh, yeah, and I don't think using an 18-foot cable is all that difficult (in fact I like it), especially compared to performing any change on the guitar's wiring ...plugging in a long cable being easier, and more reversible, than soldering a capacitor into the circuit. -Just my opinion, but, really....
    Last edited by Felix; 06-21-2014 at 07:28 PM. Reason: removed silly question

  7. #7
    Senior Member garrett's Avatar
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    Quote Originally Posted by Felix View Post
    Thanks, Garret, but won't using a resistor to lower the value of the volume pot's resistance simultaneously change its taper? -I'd rather change out the pot if I want a different value pot. As far as your suggestion of wiring in a capacitor (flip tone aside), good suggestion. I'd rather put in a better quality cap than the dollar cap you suggest; it (my CE-22) has a 180 pf round tan ceramic treble bleed cap and I don't even like seeing it in there, where a Mallory or Orange Drop or PIO should go - or no cap at all, perhaps. I still do not understand why that guitar has a treble bleed cap in the first place, '50s wiring having a reputation, along with maple, bolt on necks -which this guitar also sports- for producing a bright guitar, but I suppose PRS has their reasons for including it.

    the treble bleed cap does have a very low value... and doesn't there not being a resistor in the circuit mean that the cap is only effective during the first 1/2 of the pot's downward travel (from 10 to 5)? -Sorry for all of the questions but I'm really trying to understand.

    Garret, I think that the PDF file you referenced is the wiring I described; so that's a yes on moving the wiring? -The pot grounding and all?

    Oh, yeah, and I don't think using an 18-foot cable is all that difficult (in fact I like it), especially compared to performing any change on the guitar's wiring ...plugging in a long cable being easier, and more reversible, than soldering a capacitor into the circuit. -Just my opinion, but, really....
    I'm not sure on the taper. I've only tried it once or twice with other experiments going on. It is easy enough to swap out the pot. You could get a 300k if you don't want to drop all the way down to 250.

    Cap quality is a myth that's been passed around the guitar world. People somehow think there's "tone" or "mojo" in caps, but there isn't. What matters is the capacitor's value. The way the taper reacts may vary, but that's about it. PRS don't use ceramics just to save a buck. Think of how tone-obsessed Paul Smith is. They use ceramics because they do just fine, and there's no reason to go with anything else. All of those expensive boutique pedals are filled with cheap caps, too.

    For the HB, I'd just go with that "Current" wiring.

    And no, an 18 ft cable is no biggie. I was referring more to the dude using two of them strung together. But if the guitar is overly bright, using a cap and/or resistor in the wiring will make it "plug and play" like your other guitars. No need to switch to a different cable, redo the EQ, etc. and it's still easily reversible.
    --Garrett--

  8. #8
    Junior Member Felix's Avatar
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    The sonic qualities of capacitors is an often-talked-about semi-myth. I say "semi-" because one thing that is true is that capacitors have different tolerances: a ceramic cap generally being +/- 10%. -So not so consistent; also ceramics are somewhat microphonic. They also just look cheap; Ferrari has often used Fiat parts, and that's similarly disappointing.

    I should also mention that at the low voltages of guitar circuits, my understanding is that the material of a cap will probably have no effect upon its performance as far as tone, just its value is important in its performance (except again that ceramics are microphonic); in a high-voltage situation such as in a tube amp the cap material is much more important.

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    Junior Member Felix's Avatar
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    Oh, two other things: if I had a mint '57 Gold Top Les Paul I would rather use any length of cable rather than do the guitar the insult of rudely soldering in a capacitor, whether an NOS bumblebee, PIO, or ceramic, it matters not a bit. I don't worship Gibsons but that guitar is an investment as much as a tool, believe it. Changing the wiring is just... not done.

    Second, on "the HB", were you referring to leaving my Hollowbody (II) wired as it is, that is, "pre-2007" as far as most PRS models are concerned (the tone is (indirectly) wired to the input of the volume pot), or changing it to a '50s-style (Gibson), "post-2007" (PRS) style of wiring, so that the tone is connected (via a capacitor) to the output of the volume? I rather like it, "as is", and hesitate to fix what isn't broken.
    Last edited by Felix; 02-21-2014 at 10:50 AM.

  10. #10
    Senior Member garrett's Avatar
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    Quote Originally Posted by Felix View Post
    Oh, two other things: if I had a mint '57 Gold Top Les Paul I would rather use any length of cable rather than do the guitar the insult of rudely soldering in a capacitor, whether an NOS bumblebee, PIO, or ceramic, it matters not a bit. I don't worship Gibsons but that guitar is an investment as much as a tool, believe it. Changing the wiring is just... not done.

    Second, on "the HB", were you referring to leaving my Hollowbody (II) wired as it is, that is, "pre-2007" as far as most PRS models are concerned (the tone is (indirectly) wired to the input of the volume pot), or changing it to a '50s-style (Gibson), "post-2007" (PRS) style of wiring, so that the tone is connected (via a capacitor) to the output of the volume? I rather like it, "as is", and hesitate to fix what isn't broken.
    I was referring to switching to the "Current" arrangement as in the PDF I linked, since we're on the topic of "50's wiring". I think "if it ain't broke, don't fix it" obviously applies.

    I get what you're saying about not modding some guitars. I'm focused on practical applications right now, since LJD is obviously game to do some modding, and you seemed open to the idea, too. If you were talking about a mint '85 PRS Custom, my advice is going to change...
    --Garrett--

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    Junior Member Felix's Avatar
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    Yeah, I bought my PRS guitars new, as tools; if they work better modded I am all for it. My CE-22 just might need something changed in the wiring to tame its brightness to give it that aforesaid "plug-n-play" ability. IDK just what exactly but I am likely to try several ways. TY.

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    Junior Member Felix's Avatar
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    Reporting back: I took out my CE-22's treble bypass cap; I like the low-volume tone much better now, but I think I will fit an 80pF cap for a slightly more open sound at low volume. I am getting some variable caps in a few days; I would like to try them in my CE-22 try to find my perfect bleed capacitance.

    I also soldered a few small caps into a T/S patch cord (a guitar cable). The results were not surprising: the tone warmed up, the resonant frequency of the pups shifted to the left without the hiss of a cable... but the closest value to a cable I had was 180 pF, and one isn't enough and two is too much for my taste, so I returned the cable to stock and now use 1-3 10'-20' cables with adapters, depending on the tone I like. This is another reason I ordered the variable caps (the main one is for testing cap values in my amp).
    Last edited by Felix; 06-03-2014 at 09:07 PM.
    "We are the Borg; we operate in DC; resistance equals impedance."

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    Junior Member Felix's Avatar
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    I am a complete tyro as far as electronics, but can anyone tell me, since we're on the subject of caps: since the time it takes to charge a capacitor is different from the time it takes to discharge that same capacitor (in every capacitor to which I can find reference), would not this effect be audible?

    One wave should look "fatter" (with a fast charge time and a slow discharge time), and the reverse. This should be clearly audible and tonally significant, as it is happening real-time in the audio frequencies. -Or am I missing something?
    Last edited by Felix; 06-07-2014 at 09:30 PM.
    "We are the Borg; we operate in DC; resistance equals impedance."

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    SuperD Boogie's Avatar
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    Quote Originally Posted by Felix View Post
    won't using a resistor to lower the value of the volume pot's resistance simultaneously change its taper?
    No. The taper is established by the pot's trace and is a fixed aspect of the equation.

    Quote Originally Posted by Felix View Post
    I am a complete tyro as far as electronics, but can anyone tell me, since we're on the subject of caps: since the time it takes to charge and discharge a capacitor is different (in every capacitor to which I can find reference), would not this effect be audible?
    Not in this situation. We're talking tiny amounts of voltage where as, for example, the filter capacitors of a power amp would be storing upwards of thousands of volts. We're also talking about a different composition and type of capacitor (electrolytic vs. disk or paper in oil, etc) which are used in different circuit applications.
    Last edited by Boogie; 06-07-2014 at 09:32 PM.
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    Junior Member Felix's Avatar
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    Quote Originally Posted by Boogie View Post
    No. The taper is established by the pot's trace and is a fixed aspect of the equation.


    That just isn't true. I can find innumerable references to changing pot taper with a resistor in the literature. Putting a resistor in parallel with an audio pot changes the taper to a more linear slope.

    Edit: the opposite can be true, and depends upon relative resistor values (the pot being a variable resistor); I have measured and verified that pot taper is changed by a resistor in parallel.
    Last edited by Felix; 06-21-2014 at 08:11 PM.
    "We are the Borg; we operate in DC; resistance equals impedance."

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    Junior Member Felix's Avatar
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    Quote Originally Posted by Boogie View Post
    Not in this situation. We're talking tiny amounts of voltage where as, for example, the filter capacitors of a power amp would be storing upwards of thousands of volts. We're also talking about a different composition and type of capacitor (electrolytic vs. disk or paper in oil, etc) which are used in different circuit applications.
    I'm not talking about voltage-induced nonlinearities in fully charged high-voltage caps such as filter caps, but effects in low-voltage caps due to them being physical devices operating in a real environment; AFAICT, they are non-linear by nature, at any voltage, and this varies by the dielectric used and the other specifics of the component.

    Even at very low voltages there is still a small but non-zero charging time (in a guitar tone control (that being a (variable) resistor and a capacitor in parallel) I think it is 5 X the time constant of the cap ...but as I said this is all new to me), and it still takes time for the cap to discharge, and these two times are not equal; is a tone cap not doing this at audio frequencies? Or is the effect too subtle to hear? If someone who knows for sure could chime in that would be cool (references would help).
    "We are the Borg; we operate in DC; resistance equals impedance."

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    Junior Member Felix's Avatar
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    The whole issue of capacitor opinions and myths has frustrated me for about a year now; I finally buckled down and looked into some actual primary research on the subject, as well as a number of secondary research papers, rather than simply tertiary sources, opinion, and myth.

    If I am understanding what I have read, ceramic capacitors, because of their construction, are microphonic, and, because of their mechanical/electrochemical properties, they produce odd harmonics under voltage. The first is simply explained: the ceramic disk cap is composed of two plates of material (separated by an elastic dielectric material) which are subject to resonating and picking up vibrations, and this makes them microphonic.

    They also have a very high dielectric constant, which makes them noisy - they are made of inherently piezoelectric materials; send voltage through this device, and problems immediately start to crop up (because of the construction and physical properties of the device's components (and their interrelationships, of course)) (the plates resonate b/c of the voltage fluctuation; this attracts and repels the plates, and this produces, of course, noise) - though as I understand it, these effects are usually thought to be most noticeable in high-voltage circuits, but are still present at any voltage... and moreover (this is a separate issue, note), some caps (not just ceramics) show very sharp deviations in capacitance with variations in applied voltages, and this causes harmonic distortion.

    This last point is important to guitar tone caps: I have seen graphs showing that not only very high voltage influences cap performance, but that very LOW voltages -like those from a guitar pickup- will cause distortion as well, though the warped, s-shaped curve -which differs for different dielectrics, of course- is opposite for low and for high applied voltages. I will try to be clearer: at very low voltages, some dielectrics, and here speaking of caps in general and not specifically of ceramic disks, will show marked swings in capacitance under varying voltages (AFAICT a "perfect" or non-varying dielectric does not exist in the physical world, though this variable capacitance curve can be and is very regular and shallow with some dielectrics and construction methods). At low voltages, these "high-variation" dielectrics show quite a bit higher-than-rated capacitance, and at high voltage this curve reverses. This swing from high-capacitance to low-capacitance can be quite sharp in these dielectrics, especially at low voltages.

    Ceramic disks have been shown to produce harmonics in the odd series (I have not seen an actual explanation for this but it seems to me that the odd harmonics are produced b/c the plates are equal (to fair precision) and opposed (again, with pretty fair precision), cancelling out even harmonics, but this is ignorance and speculation on my part). In any case, just b/c of their microphonic properties, I will be avoiding ceramic disc caps in the audio path (except maybe for the NFB path in my amp; I might want to see if applying the "extra" odd-series harmonics as negative feedback to the P.I. tube will attenuate the "naturally-produced" odd harmonics).

    MLCCs, AFAICT, are only microphonic with a bias voltage applied to them (although they are piezoelectric (all caps are), and thus show additional noise (that is, additional to the basic "thermal" or Johnson–Nyquist noise and the schottky (or "shot") noise (which is present in all conducting materials and is due to quantum fluctuations)). If you want a tiny cheap cap in a guitar circuit, an MLCC might be okay.

    Opinions seem to be divided upon the audio qualities of silver mica caps in both the guitar and audiophile communities. Some like their treble response and some find it harsh. I can't find a good explanation for this but I have seen it suggested that their low noise in the upper registers makes them sound both clear/digital and harsh/digital. The pink noise produced by (the wonderfully inefficient) carbon comp resistor is similar to this phenomenon, I gather. It is speculated that it is this quality which makes which makes carbon comps seem seem warmer and more pleasant than resistors producing less noise or equal distributions of noise (white noise), but this is psychoacoustics, not engineering... but I digress.

    Will I pay $20.00 for a NOS PIO cap? well, um, no. For one thing, if it hasn't been in a circuit with voltage running through it, its value is likely to be off to a greater degree than if working, and it is much more likely to be leaky. NOS parts can look lovely but are quite expensive; there are modern parts which perform quite well, even if what you are looking for is a very inefficient part. Some people like the sound of class-A amps (I am among them, but chose to go the route of a pseudo-SET 3-way conversion mod combo to my to my push-pull EL-84 amp, which is quite complicated, but a real blast to do, and allows me infinite variation among 24 distinct power-section circuit topologies (running in four modes), ranging from pentode push-pull to single-ended triode amp (either tube, and yes, they bias right and get the full signal from the P.I. tube)... and I don't need an air-gap tranny!), and they are extremely inefficient from an engineering perspective, but generate even harmonics much better than push-pull topologies (push-pull topologies cancel out even-series harmonics (if well-balanced), as I said before - and as most of you surely know).

    Poly caps seem best to me, without going into PIOs. They have good physical and electrical qualities. Remember I am a tyro. Upon the subject of PIOs and such I really need more info. can anyone help?

    The cap time constant question still bothers me; I can't find an answer to it. Ditto plaintive "can anyone help?".

    Anyway, sorry if I seemed snotty before; I don't mean to be brash; I do really want to know all this stuff, and I am an almost complete novice at it. In addition, I cannot do math to save my life. (Despite that, I get by.)

    For the record, my cables run circa 10-15 pF/foot + ca. 10 pF/connector. They weren't "expensive", in that I have like, 60 of them, and have for like, ever, so no added expense was necessary to simply plug cables together - and it was a heck of a lot easier than learning to solder, too (I would have never done that without the above challenge to solder a cap into a cable ("cheaper" my a$$! -The soldering iron and solder were cheap, but not free)). ...And I only had two capacitors at the time, one in my CE-22.

    Also for the record, and re the treble bleed issue (if not the actual wiring considerations), and if anyone cares (as if, Felix!), I have wired up a varicap as a diagnostic device, but have not used it for my "'perfect' treble bleed cap value" determination yet (ah, psy parties and anime... and legal troubles, oh my!), but I have used it as a diagnostic tool on my amp's smaller cap values... it works. Update soon on treble bypass values as Felix prefers and as determined by NOS varicap (2 for $5.00; I've paid twice that for one modern wirewound resistor!). I have two air-gap variable caps coming which are of higher value and wider variation (my present caps only go from 20-386 pF; these are 20-680 pF or so) -and which can take the 650V I need them to! ...This sort of component could be a quite effective, if trivial, tone control if applied between the guitar out and the amp.



    Edit: I should have said "it would have been a while before I first picked up a soldering iron"; I would have been modding my amp before too many more years had passed, probably. Still, the push was appreciated.

    Edit: I should have said that push-pull topologies cancel even harmonics generated in that stage.
    Last edited by Felix; 06-19-2014 at 12:35 AM.
    "We are the Borg; we operate in DC; resistance equals impedance."

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