Sujet Potard et micro double

Citation : Why do Fenders have 250k pots while Gibsons have 500k?
Pickups have 2 loads - volume pot resistance and guitar cable capacitance. The volume pot forms a Low Pass Filter (LPF) with the pickup inductance and the cable sets the resonant frequency (Rz) of the pickup. The LPF formula is freq=R/2piL 1. for Fender Strat R=250K L=2.4Henrys Rz=16.57KHz 2. for Gibson P-90 R=500K L= 5.7Henrys Rz=13.95KHz It can be seen that both pickups start to roll off highs at the upper limit of our hearing at about 14Khz. Given the frequency response of the average amp and speaker this won't be heard! Now let's connect a 250k pot to our P90 pickup to see the effect of pot load- R=250K L=5.7Henrys Rz=6.98KHz!!!!! An Rz of 7Khz would definitely be heard as a loss of brightness compared to the Rz with 500K! See also Tone Workshop >Perfect Guitar >Pot values

Answer supplied courtesy of Colin Bloxsom, Guitar Tek/Fx designer-Sydney, Australia.

Citation : Pot values: Ever heard the old guitarist proverb..."if it ain't got it in the first place you can't boost it later"?
Forenote: 'A' curve pots are Audio taper (or Log curve) which means they operate in a such a manner as to be in unison with the way the human ear detects changes in loudness. The great majority of Guitar Players prefer 'A' curve pots but occasionally one will prefer Linear pots.

Volume pots:
Higher value pots and capacitors cause the pickups to resonate at a higher frequency and develop more output and presence with the result that the sound is noticeably brighter. Lower value pots and capacitors have the opposite effect and push the sound towards the duller end of the spectrum with lower output. Knowing this is helpful if you want to experiment with pot and capacitor values to change your sound.The value of the Volume pot is crucial to pickup performance. A lot of pots, although labelled as 250K, actually measure much less (Eg 217K, and recently I measured 3 new Fender CTS pots at 117K) but very ocasionally they measure more (Eg 265K). Players should understand that a great pickup can be muffled by a pot that measures low, causing a muddy sound. The first thing that suffers is the AIR and Presence of a pickup. Since these are two of the most important performance aspects of Fender pickup sound it's actually a minor tragedy when these are sacrificed.

Citation : Control Values
Should I use 250K or 500K controls?

Regardless of what type of pickups are in your guitar, higher potentiometer resistance values produce a little more power and treble response. Whether this is a good or a bad thing is a matter of individual taste. In the early days, Gibson used 500K controls and Fender used 250K, thereby starting the single-coil = 250K, humbucker = 500K theory. Even though neither company has stuck strictly with this formula since then, the theory lives on. You won’t damage your pickups or your amp by mixing and matching different value controls, and one of our current favorites is a 250K volume control and a 1 Megohm tone control, EP1202.

Citation : VOLUME Control control: (Treble Bypass filter -or- treble bleed filter)
I get asked a lot about how to stop losing treble/presence when the volume is turned down. Kinman AVn pickups don't suffer from this phenomena to the same degree as regular single coils, in fact many Kinman owners tell me they noticed the problem disappear when they fitted their Kinman's. This device, when used with Kinman noiseless pickups, actually increases the brightness slightly as the volume pot is wound down, making it great for volume reduced rhythm chops. When used with regular non-noiseless single coils it attempts to preserve the amount of brightness as the volume pot is wound down.But if you have this problem and want to reduce it I devised a little circuit that helps. It is simply a .0012uF (1.2nF) 630* volt Polyester capacitor in series with a 130K Ohm resistor (1/4 watt) that is wired across the two hot terminals of the volume pot (*any voltage cap will work fine but 630 volt caps have thick wires that are easy to work with. In the diagram it says 63 volt, it should be 630 volts). A rudimentary way of looking at it is the cap allows some of the high frequencies to pass around the volume pot direct to the output and the resistor limits the amount of them that get past. The capacitance can be varied slightly from .001 to .0016 to fine tune the circuit to your cable, but you will have to increase the resistor value with the larger cap values and decrease the resistor value with the smaller cap values or else you will notice the curve of the pot starts to become noticeably different with the larger cap values. It's a delicate balance so deviating from the nominated values may excessively flatten the operating curve of the pot unless you compensate with the resistor value. Read more technical guff about this on the FAQ page Q24. Rule of thumb is the *amount* of brightness that is gained is determined by the resistor's value (less Ohms = more brights) but the frequencies that are present is determined by the Cap value (lower the value the higher the frequencies, the higher the value the lower the frequencies).

By the way, this design works better than a 'capacitor' only -or- the parallel 'resistor/capacitor' design that some makers fit to their guitars, so if you didn't like theirs try this one. These circuits, including mine, are quite crude and won't suit all conditions. They leave very little latitude in deviating from the nominated cap value. You will have to experiment to arrive at the perfect value for your cable. To save time in experimenting you can run some wires out from the volume pot under the edge of the pickguard then you can connect various value caps and resistors to the ends of those wires in a matter of seconds. When you get the right combination they can be soldered to the pot terminals.