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Different Value Pots= Different Sound?


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getting into an earlier topic about inreasing the highs of my pickups i decided an experiment with my new jazz.

i wired the neck in 250 and bridge in 500, in an attempt to exagerate the different tones.

they actually sound a lot closer sounding togehter than another jazz i wired with both 250k;

is there something happening here that is maybe combining the values to one average one?

seems impossible; but so does my results;

maybe some way to run them individually to the input so the 2 values never directly connect?

thanks

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There is some debate and mojo about different cap types, generally though a cap is a cap, the biggest differences tend to be the tolerances...how close they are to what's written as their values...but in simple passive circuits there really isn't a lot of difference...

As Wes points out though, there can be a huge difference in the effect different values have...

There is a big difference between the cap in the tone control and the treble bleed though...which is what these are designed to do...

This is a good reference though for the treble bleed values between bass and guitars that are commonly used.

Pot values are similar...it's worth thinking about how there things work...some of it seems a bit anti-intuitive...

A pot is a variable resistor, a resistor resists the flow of electricity...so a pot so a bit like a tap.

So, in a typical circuit, the pot connects the hot of the pickup coil to the ground,,,so effectively bridges the pickup coil...when the pot is turned to zero...the sound is off...

Think about it...what is happening is that the pot is turned from it's biggest valued (say 500K, 250K or whatever) to zero resistance...it therefore creates a short across the output of the guitar and you get no sound...

A HIGHER VALUE POT when wide open (full volume) will show MORE resistance between hot and ground...so a higher value will ground less, and in these circuits, this largely effects the highs...

So, you can brighten up an HB say, by using 1M or 1 mega ohm (2x500k) value pot...so higher values pots generally mean, more highs when wide open. On a single coil strat, perhaps you will want the edge taken off, so 250k is typical, with HB's 500K is typical...and so it goes.

A TONE POT...should have little if any affect when wide open...it's still a resistor so there will be an effect...and the volume and tone will interact to a degree...but what is happening here is that the resistor is showing less resistance between a cap and ground...the cap allowing the highs to be grounded and the resistor (pot) and cap in this will affect the way the tone control rolls off highs.

Small caps can often produce a pronounced wha type effect in the lower range of the guitar and can be a cool effect as wes found out...but a lot of the pots travel may do little...depends what you want from the operation of the tone control.

The TREBLE BLEED CAP often combined with a resistor, has almost the reverse effect of the tone control...as the volume pot is turned down...less resistance, it still allows for the high frequencies to 'bleed' through...so as you turn down the guitar, instead of getting muddier, it gets brighter...or seems that way, it just retains the highs and turns down the lows first.

A lot can be done with experimentation (or conventions) and of course on a bass, completely different frequencies and so different values are used.

Without a selector switch...you can't isolate one pickup, pot and tone circuit...so it is effectively like an LP with both pickups on...

If you think about it...when you turn either volume down towards zero, you are creating a short across the output...whcih of course silences the guitar...the idea with these things is to mix pickups with the two volumes to get the kind of sound you are after from multiple pickups. The combination of the two pots then do interact...the manner in which they do and the sweep of the controls, the amount of 'bleed' or roll off on a tone control, is a mix of all the values of components used...

There are no 'hard and fast rules' and in fact, different pickups (which adds a big induction coil into the circuit) will have different effects and perhaps require different strategies.

You will notice that a lot of basses use active electronics...this will allow separation and even tone boost (passive circuits can only bleed frequencies to ground, they can't add anything) as they have an effective mixer on board.

So...this is a very little potted overview, it is probably worth reading up and exploring circuits, or even getting a few caps of different values (they are silly cheap...stew mac is selling components worth 5c in an electronics store for over $5 here!!!!) and trying things out.

But the answer is that there is an interaction...at zero resistance on either pot, you will get a complete short and so no sound...but the secret to working these things is in the mix...pot values are only a part of teh equation, and effects the interaction...but higher value pots typically show more resistance and so retains highs...a treble bleed network will allow the highs to be retained as you turn down the volumes (rolling off the lows) while the tone control does the reverse. The tone control should have little to no affect when on full...so there is not "tone" advantage with different mojo infused caps, at the very least, not till the controls are turned down and even then, it is far more the value of the caps (along with the pot sweep and the pickup coil specs) that creates the tone control effect (ie tone control...not TONE).

Sorry though, can't advise as to what cap or pot values, especially in a bass, you are likely to want or even the affect you are after...the previous thread seemed to imply you were after more highs, so a bigger pot value, or just a treble bleed network suitable for the bass, should get you in the ball park for that kind of effect.

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I think you really should look at Caps rather than pots. I have been meaning to setup a test neck and place different caps on a rotary switch so I can see whats changes they make.

I have never seen anyone play with pot values as a sound enhancing solution. I think caps give you a quick and cheap way to adapt your sound.

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yes yes, all very true; but.... my 'question' was about the 'change' that did occur.

jazz #1 - 250k 250k 250k (vvt) huge difference between neck and bridge pup; like any jazz; bright bridge muddier neck

jazz #2 - 250k 500k 250k (vvt) no discernable difference between the tones of either pickup

its just wierd; thought i wondered into a wiring no no for keeping the seperate tones;

but thanks

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this is copied from another forum. Take is as face value as I do not know if it is true or not. the link is below

general "rule-of-thumbs":

1Meg = very bright sounding

500K = bright sounding

250K = warm, vintage sounding

1Meg = bright HB...shrill SC

500K = warm HB...bright SC

250K = muddy HB, warm SC

HB = humbucker

SC = single coil

...the HIGHER the pot resistance value, the LESS high-frequencies are attenuated.

...the LOWER the pot resistance value, the MORE high-frequencies are attenduated.

TONE control pot value doesn't matter too much because the overall "taper" or "rolloff" can be 'adjusted' by simply changing the cap value.

The value of the tone pot when it is fully open has exactly the same loading effect as that of the volume pot, and in fact does not depend on the value of the cap (for usual values), which only affects its response when you turn it down. In other words, a single 250 k vol. pot will produce the same amount of treble rolloff as a 500k vol. pot and a 500k tone pot (in all cases with the pots at maximum) since the parallel of 500k and 500k equals 250k.

You can see this effect and also the one explained by Jim in my simulation spreadsheet: www.harryj.net/voltone.xls. The default pickup parameters are for a vintage humbucker, use pickup L = 2.8 H and pickup C = 60 pF for a typical single coil.

you can read more here

http://www.thegearpage.net/board/showthread.php?t=59038

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right on the head woodenspoke. http://www.tpub.com/neets/book1/chapter3/1-26.htm for parallel resistance formulas. what i have found is that either control the tone massively from your guitar or minimalistic. if its massive then go active. if its minimalistic then go passive and remove the old tone controls and seek other methods than simple caps to ground. look at some of the posts recently like my lespaul acoustic wiring or low end fuzz varitone post we put some great stuff up there.

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In passive circuits, caps and pots can only take away...so a tone pot will bleed the trebles to ground to change the tone that way, with a treble bleed volume, the bass is attenuated while the trebles remain....but in both cases there is a loss, of highs in one, and in volume in the latter (leaving in more highs)...the only solution is active...

The rest is much as I said, higher pots values will attenuate less to ground even when full up. Even though a 250k pot will have 250K resistance between a full short (zero resistance, or the pot turned to zero) there is still a connection through the 250K resistor to ground. To get the full effect of 'brightness, have no pots at all and connect directly to the output jack! However, a 1Meg pot will achieve a similar result.

I think what you found was that by using a mix of controls, the 500K pot may have brightened up the neck and the 250K taken off the treble...resulting in a similar sound...by the position along the string, the neck pickup is going to get more fundamentals that the bridge which will have more harmonic content in the higher frequencies of the note...a more complex sound. The ear is also more attuned to these sounds and more so with a bass.

...

I'd still recommended playing with treble bleed things and turning down the volume on the instrument...and turning the amp up to compensate...and/or...changing to much higher values such as 1Meg pots to let as much highs as possible through, and rolling off them as appropriate with the tone.

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