# the 250K or 500K pots with P90's thread



## GTmaker (Apr 24, 2006)

SO whats the deal with P90s and the use of 250K or 500K pots.
Which pots do what?
What do you use and why?

All responses welcomed.


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## keeperofthegood (Apr 30, 2008)

GTmaker said:


> SO whats the deal with P90s and the use of 250K or 500K pots.
> Which pots do what?
> What do you use and why?
> 
> All responses welcomed.



Ya'know for all the virtues of the THIS and the THAT why are people not making/using a push/pull dual pot with a 250K and a 500K wipe. Would so expand choice with a minimum of extra work.


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## cwittler (May 17, 2011)

500K pots = brighter tone, usually.


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## keeperofthegood (Apr 30, 2008)

Ok I think I have an idea here but bear with me.











Get a 500K of this. Get a 510K resistor. Place the resistor across the bottom pair of switch terminals (side does not matter here). The pickup hot to the top switch terminal and to the onside of the pot. The ground side of the pot to the bottom switch terminal. Center lug on out. When the switch is in one position, it is a 500K pot, in the other position it effectively becomes a 250K pot.


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## blam (Feb 18, 2011)

if 500K is too bright, just dial it down.

if 250k is not bright enough, just turn it up, oh wait... you cant. go 500k.


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## mhammer (Nov 30, 2007)

For the 917th time, higher value pots will provide less loading and retain more of the pickup's natural brightness _if they are turned up all the way, and you rarely or never lower your volume control_. They will NOT do that against all possible odds, and in the face of all possible settings.

With the pot turned all the way up, the amp (or the first pedal) "sees" three things at the guitar output jack. It sees 500k to ground from the volume pot, 500k and the tone cap to ground, and the 8k or so from the pickup. Compared to the tone and volume pots, the 8k is a tasty offering, sot he amp gives preference to that.

Now, let's turn down the volume a bit so that 100k of the volume pot is placed in series with the pickup, and the other 400k goes to ground. When the amp looks at the guitar, it sees 108k (pickup + volume pot portion), and 400k to ground. The pickup is no longer the big bargain it used to be, and the loading effects kick in.

The anti-loading function of higher-value volume pots is a real thing, but it is of minimal value if one is the sort of player who likes to keep the volume below max a significant chunk of the time.

Fender addressed that issue by means of a bypass cap between the volume-pot input and wiper. At high frequencies, that cap acts like a zero-ohms path, so that if the 250k volume pot is turned down to, say half, the amp still sees something like 6.5k along the pickup path (for high frequencies) compared to the 125 to ground provided by the pot. The bypass cap allows for the SC user to get the "benefits" of loading that 250k pots provide at max volume, while not forfeiting top end too much when turning down.

T'wer I, I think I'd opt for a 500k volume pot, and use a push-pull switch pot for tone that provided or removed a bypass cap on the volume control, depending on my mood and needs.


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## bagpipe (Sep 19, 2006)

So if I always play with the volume and tone pots maxed out, I could effectively remove them and achieve the same effect ie just wire the pickups directly to the output socket (via the switch I guess, so that I can switch between the pickups)?




mhammer said:


> With the pot turned all the way up, the amp (or the first pedal) "sees" three things at the guitar output jack. It sees 500k to ground from the volume pot, 500k and the tone cap to ground, and the 8k or so from the pickup. Compared to the tone and volume pots, the 8k is a tasty offering, sot he amp gives preference to that.
> 
> The anti-loading function of higher-value volume pots is a real thing, but it is of minimal value if one is the sort of player who likes to keep the volume below max a significant chunk of the time.


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## mhammer (Nov 30, 2007)

Pretty much. Your amp or pedals would "see" whatever their input impedance is.


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