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Treble bleed mod.. which one is the best?

Discussion in 'General Electronics Discussion' started by electronoobz, Dec 13, 2012.

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  1. electronoobz

    electronoobz

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    Jan 14, 2012
    i saw it here : http://www.projectguitar.com/tut/potm.htm

    i have a guitar with a 250k vol pot and 250k (yeah, i think.. but i know it's 500k)..

    i want to mod it.. hmm

    which of those 3 could i use?

    can you explain the differences please?

    this is my first time to do a treble bleed. haha so excited! :DD
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,413
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    Nov 17, 2011
    What exactly is the question?

    If its for the value of potentiometer to choose, I can't help.

    If it's for the value of the paralllel resistor to an existing potentiometer, that's easy:
    Rtotal= (Rpot*Rpar)/(Rpot+Rpar).
    So if you have any two values (say the expected total resistance Rtotal and the potentiometer's resistance Rpot, you can easily find out which resitance Rpar to connect in parallel.
     
  3. electronoobz

    electronoobz

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    Jan 14, 2012
    no what i mean is what of those 3 treble bleed method is the best i can use with my pots in my guitar
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    The guy who wrote that tutorial doesn't know much about electronics. Don't take too much notice of what he says.

    The so-called "treble bleed" modification involves putting a small-value capacitor, around 1~2 nF (".001", ".0012" etc), optionally with a resistor in series with it, between the signal end of the volume potentiometer on a guitar, and the wiper. This gives some treble boost and "brightness" to the sound over a moderate range of adjustment of the volume control.

    When the volume control is at maximum, the capacitor will have no effect. It will have maximum effect when the volume control is in the centre position. It is a "hack", in that it doesn't give a consistent, definable effect. But as long as you keep the volume control between around 25% and 75% of scale, the effect will be noticeable.

    The choice of capacitor value, and the value of the series resistor, if any, depends on the resistance of the potentiometer, and on how much treble boost you want. It will also depend somewhat on the output impedance of the pickup. It is difficult to calculate exactly, but you can estimate it using a circuit simulator such as LTSpice, which is free and can be downloaded from www.linear.com. If you haven't used circuit simulators before, there is a bit of a learning curve.

    In general, a higher capacitor value, and a lower series resistor value (no series resistor is the lowest series resistor you can have - zero ohms) will have a greater effect.

    No one else can tell you what capacitance and resistance are "best" for any particular situation - it depends on what you like the sound of. So I suggest you try all three and choose the one you like the sound of most.

    While testing, you can also adjust the volume control (adjust the gain on the amp to compensate) to see the difference that the volume control position makes to the sound.

    Edit: Oops... this is the most embarrassing mistake I've made so far on these forums... The volume control will have a log/audio taper (often indicated by the letter "A" after the resistance value marking). This means my advice about the "treble bleed" mod having the most effect when the volume control is near the middle of its "range" actually apply to the RESISTANCE range, not the rotational range. So it will have the most effect between, say, 40% and 90% of the rotational range.
     
    Last edited: Dec 14, 2012
  5. electronoobz

    electronoobz

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    Jan 14, 2012
    hmm.. ok wait.. for a 250k pot volume.. which method is the best sir?

    the series or the parallel one? or maybe the cap only?
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Try them all and choose the one you think sounds best.
     
  7. Raven Luni

    Raven Luni

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    Oct 15, 2011
    I've recently found that guitar guys and electronics guys rarely get along. Try talking theory in a guitar forum to see what I mean :p

    Anyway, from what I've been able to figure out, the pot value is somewhat related to the pickup. 250k, 500k etc. seems to be more of a modern preference, whereas values like 50k are much more common in vintage guitars (like my dads guitar that I just rewired). If you look at this site about pickup winding, you'll see that the pattern tends to be that the resistance of the pot seems to be proportional that of the pickup (or is that inversely proportional).

    The other thing to remember is to always use logarithmic tapered pots. You will also see some labeled 'audio taper' - this is basically the same thing but more refined (log pots arent truly logarithmic but tend to be made out of linear sections joined together and the 'audio' ones are truer to the curve).

    For further reading, look at passive filters. This is basically what your tone control does and having a basic understanding will enable you to do alot more than the site you linked to :)
     
    Last edited: Dec 13, 2012
  8. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Thanks Raven Luni.

    I'm a musician as well as an engineer, but I know what you mean. That's why my recent reply was so brief and to-the-point.

    Thanks for pointing out that the volume control will be log taper. I knew that of course, but somehow I didn't think of it!

    The resistance of the volume pot should be nominally directly, not inversely, proportional to the impedance, not the DC resistance, of the pickup.
     
  9. Yoa01

    Yoa01

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    Jun 18, 2012
    I've actually experimented with this a bit in a variety of guitars and found that *most* of them work really well with a 2nF cap and a 100k resistor.

    If you really want to get into some modding, You can replace your tone control with an RC low pass filter using a 220nF cap and a 100k pot. You can be really fancy and set up an RC-filter-based 2-band EQ (same specs). If you want a warmer sound, you can put a single diode clipper at the output.
     
  10. electronoobz

    electronoobz

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    Jan 14, 2012

    more detailed pls... uhm scheme?

    i have single coils in here matched with 250k vol pot for warm sound and 500k in tone pot.. should i really lessen it? lessen it to 100k?
     
  11. electronoobz

    electronoobz

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    Jan 14, 2012
    uhm guys.. may i know the diff. between the caps and res installed in series and parallel?

    does the parallel one cut out high ends quickly? or what?
     
  12. Yoa01

    Yoa01

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    Jun 18, 2012
    Sure thing, mate!

    Here is my personal design for a guitar I'm building:
    [​IMG]
    The input, 'from Alumitone' (I'm using an Alumitone pickup), goes into the 20k volume pot with the treble bleed circuit. That then goes into a passive RC lowpass, then highpass, filter, creating a kind of 2-band EQ. That output then has a switch to turn on or off the diode clipper, which warms the sound and clips slightly when you play loudly.

    The difference between parallel and series is tone. In series, you will get a more trebly sound due to the highpass nature of capacitors. In parallel, you get a thicker sound and easier control.
     
  13. electronoobz

    electronoobz

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    Jan 14, 2012
    thanks!! love that.. hahahaha.
     
  14. Yoa01

    Yoa01

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    Jun 18, 2012
    Not a problem. Neat thing is, this circuit works with every guitar, bass, and synth I've tried it with. It's a multitasking tone controller!! haha It also works as a standalone unit, maybe for like a DIY radio or whatever.
     
  15. electronoobz

    electronoobz

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    Jan 14, 2012
    btw why do you 3 pots in there? 2 100k? and 20k pot for volume?! hmm.. weird.. never saw anybody used it.. the lowest possible i know is 250k..

    aynway it is your preferred configuration so i wont argue with it..
     
  16. Yoa01

    Yoa01

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    Jun 18, 2012
    It is weird, I know. The 100k pots are there so that you get a decent range with the filters. The 20k pot was chosen because, if you look at it, it is a crossfader between the input and ground. 20k gives the best response over the range. Much larger and you would have a kind of flat section near the middle of the sweep where the volume doesn't really change much. All pots are linear, though.
     
  17. electronoobz

    electronoobz

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    Jan 14, 2012
    thanks again.. seems like you are good at this one huh? you are the only one who has a better response.. hehehehe
     
  18. electronoobz

    electronoobz

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    Jan 14, 2012
    where does the p3 connected to? i mean is the upper pin... i saw where the wiper and the ground lug is going... but how about the other one? sorry for inconvenience
     
  19. Yoa01

    Yoa01

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    Jun 18, 2012
    Hardly. See my signature? I achieve almost everything through trial and error. I'm a musician, and since a lot of music stuff is electronic, I figured I would get into audio electronics. So far all I can do is simple stuff -- the most complex thing I've built is a small drone synthesizer. I've been at this for 8 months, this is the best I've got :)
     
  20. electronoobz

    electronoobz

    226
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    Jan 14, 2012
    hey sir.. where is the other pin of P3 (100k) going?
     
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