guitar volume, bypassing cap

[geetarpicker]

The cap is just straight across the hot and ground. I may make a rotary switch box as well, as 3000-3500pf works well with my strats but seems a bit too much for my LPs.

[Fredaxis]

I have a "PRS sweet swich" to install in one of my guitars, for testing....
It is meant to sweeten the high end by replicating the effect of long cables ... guess I should measure the capacitance of this little black box.

Thanks for the tip Glen. ( I love your CD)

[gearhead]

The cap is just straight across the hot and ground. I may make a rotary switch box as well, as 3000-3500pf works well with my strats but seems a bit too much for my LPs.

Hmm, since the rest of us wouldn't be modding a historical artifact, this could be done on the input and made switchable!

[FUCHSAUDIO]

I used to take a capacitor substitution box, and used it to sub both the tone cap and the shunt cap on the volume control. It's really a nice way to dial-in the right values for the tone you want. There's no "right value", as cable capacitance, and the amp you use, the pickup type etc, can all affect it.

I've also experimented with the actual volume control pot value. If you put a 1-M pot in parallel with the two outer legs, and adjust it downward, you can trim your guitar pot value downward, and hear what the loading does to the pickups tone.

[klingo]

El_Martin wrote:
that is: cap connecting input and middle lug of a volume pot.
Gives a paralle path for the highs to bypass the pot.

have you the 50's wiring

[Dai H.]

some related links on cable cap/pickup interaction:

http://terrydownsmusic.com/technotes/gu ... cables.htm

http://www.buildyourguitar.com/resources/lemme/

http://www.buildyourguitar.com/resource ... /table.htm

(couldn't find the link for this but had the info in hand) :

Bill Lawrence

USA


Nov 17th, 2003 08:13 PM Edit Profile Print Topic Search Topic
Cable and Sound

Cables, by themselves, don’t have a specific sound but can alter the sound of your guitar dramatically. To give you a better understanding, let me explain the basic function of pickups and cables:

1. A pickup is a cored inductor that converts the mechanical energy of the vibrating strings into an electrical signal. A pickup has inductance and resistance.

2. A cable is a tubular capacitor that transmits the signal from the pickup to the amplifier. A cable has resistance and capacitance.

In combination with a high impedance system, like a pickup, the resistance of the cable is too low to influence the signal; but in a low impedance system, like a speaker, the resistance of the cable is critical.

The sound of an electric guitar depends mostly on the frequency, the intensity and the bandwidth of the resonance. The resonant frequency (Fr) is the result of the interaction between the Inductance (L) of the pickup and the Capacitance ( C ) of the cable.

Fr = 1 / [ 2pi X L^ ? X C^? ]

With this simple equation, it’s easy to calculate the Fr when the values of L and C are known. However, to calculate the shifts, the bandwidth, and the intensity of the resonance, which depend on the Resistance
( R ) of the circuit, requires some extensive knowledge of electrodynamics, but you can hear their shifts by slowly turning down the volume control of your guitar.

There is neither good nor bad inductance or capacitance, and when it comes to sound, we all have different preferences -- what Charly calls a fat, creamy blues sound, Johnny may call it a dull or muddy sound. Till the early ‘60s, most cables were between 8 and 10 feet long and had an average capacitance of some 300 pico farad. Combined with a Strat pickup having an average inductance of 2.4 Henry, the resonance was around 6000 Hertz. Then came these spiral coil cords with a capacitance of 2.4 nano
(2400 pico) farad shifting the resonance of a Strat a little above 2000 Hertz.

You might ask, “How does this effect my sound?”

Due to the resistance of a pickup and the load resistance of the controls, we increase the bandwidth of the resonance, causing an output boost in the vicinity of the resonance. If the resonance is above 5000 Hertz, it’s barely noticeable and may increase the sparkling highs, especially with 500 K’ohm controls. Shifting the resonance to lower frequencies results in increasing brightness, and at about 3000 Hertz, you’ll get that famous “ice pick” sound, especially with the bridge pickup. Below 2800 Hertz, the harshness slowly disappears and below 1000 Hertz, the sound gets muddy. Try it....turn your tone control to zero and with a .022 cap, the resonance will be at 700 Hertz; with a .05 cap, it’s at 450 Hertz. Now, replace the cap at the tone control with a 2.4 nano farad (.0024 micro farad) cap, turn the treble and volume of your amp above 8 and you might get a bit closer to some of Jimi Hendrix’s sounds; but don’t forget he also used some cables with a much lower capacitance. However, just recently I saw somebody offering a 12 foot cable with a very high capacitance for above $300 and promising the Jimi Hendrix sound. Capacitance is capacitance, and you can get the same effect with a 2.4 nano farad cap for less than 50 cents.

The higher the inductance and the higher the capacitance, the lower the resonance. This explains that the same pickup can reproduce a sweet tone, a bright and harsh tone, or a compressed and muddy tone -- it all depends on the capacitance of the cable and the load resistance of the controls.

As a player, I’ve always preferred cables with a very low capacitance because I could tailor my sound using additional caps, inductors and resistors in the circuit. For that reason I introduced low capacitance cables in 1978. (At that time, George L was my exclusive national distributor for my products.) Today, there are quite a few good and inexpensive cables available with a relatively low capacitance.

It would be nice if all cable makers would publish the capacitance of their cable to allow you to select the right one for your needs.

Bill Lawrence

http://www.billlawrence.com

(This message was last edited by Bill Lawrence at 08:27 PM, Nov 17th, 2003)

[jerrydyer]

220k res/ 680pf cap

[El_Martin]

Hi!

@klingo
Yes, I rewired my LP special copy to have the tone pot after the volume pot. And there is only one volume and one tone pot for both pu.
Sounds nice with some other amps

Ciao
Martin