Can someone make sense of this wiring diagram?

[stratomaster]

http://prsguitars.com/csc/schematics/santana.pdf

http://prsguitars.com/csc/schematics/santana.gif

I'm trying to figure out what the trim pot and fixed value resistors do. If anyone can help me out, I'd really appreciate it.

Thanks!

[David Schwab]

The fixed/trim resistors are going between the the lead pickup and ground. This is probably to load the pickup down a bit to roll off some top end. If you remember, PRS used to have a circuit called the "sweet switch" which did something similar. Santana had complained that when he used a wireless system the guitar was too bright, so the sweet switch simulated like 100 feet of cable. I'm guessing this is doing something similar.

But I think this schematic is wrong, as one combinations of the switches mutes the sound.

If you compare that schematic to this one:

http://prsguitars.com/csc/schematics...8/santana1.pdf

The ground connection between the 470K resistor on the neck pickup to ground is missing.

The bridge pickup always has the load on it.

[stratomaster]

I think "standby" mode was a feature of the Santana I. So using resistors instead of low value caps can accomplish similar things? Thanks so much for helping me out.

[Mike Sulzer]

I think "standby" mode was a feature of the Santana I. So using resistors instead of low value caps can accomplish similar things? Thanks so much for helping me out.

No, they are not the same thing. Adding cable is like adding capacitance. It lowers the resonant frequency. Loading with a resistor lowers the height of the resonance. Both get rid of highs, but they do not have the same frequency response function and generally sound different. In some cases they could sound similar enough so that you could use either.

You mean those wireless things used with a guitar do not have a circuit at the input to simulate a cable? That is dumb.

[David Schwab]

I think "standby" mode was a feature of the Santana I. So using resistors instead of low value caps can accomplish similar things? Thanks so much for helping me out.

Well if there is a mute position, it is the first schematic with the ground attached to the 470K resistor from the neck pickup.

That's what I had said earlier.

So the resistors are to "warm" the tone up.

[David Schwab]

You mean those wireless things used with a guitar do not have a circuit at the input to simulate a cable? That is dumb.

No, they don't. Or at least they didn't then. They might now. I'd imagine the wireless makers considered cable bad, since the wireless was getting rid of it.

Originally PRS used a passive delay line module to simulate the extra cable.

[stratomaster]

Are you all sure they aren't in parallel? The more I looks at it the more it seems to me like they are being used as tapering resistors. One value/taper for volume pot on neck pickup and another on the bridge. They seem to be in parallel to the circuit not series like the volume pot is.

[David Schwab]

Are you all sure they aren't in parallel? The more I looks at it the more it seems to me like they are being used as tapering resistors. One value/taper for volume pot on neck pickup and another on the bridge. They seem to be in parallel to the circuit not series like the volume pot is.

The resistors? How are they in parallel? Parallel to what? They aren't in series with the pickup signal though as I first posted, they are connected to ground.

Look at the bridge pickup. The hot lead of the bridge pickup goes through the trim pot and resistor, and then to ground on the back of the volume pot. That's loading the pickup down. The rim adjusts how much of an effect it has on the tone of the pickup. It has nothing to do with taper on a volume pot. The 470K resistor on the neck pickup also goes to ground. Same deal. None of them have anything to do with the volume control, and they aren't even connected to it.

Am I sure? Absolutely. I drew out all the signal paths for each switch position. That's the only way to check what's going on. There is only one connection to the volume pot, at the wires between the volume and tone. The output from the switches connects there. That's the signal from the pickups.

In the first link you posted, one set of switch positions acts like a kill switch and mutes the guitar. That's what you said was a feature.

If you want to change the taper of a pot, you need to connect resistors between the lugs on the pot, not between the pickup hot leads and ground.

Here are the switch positions from the first schematic:

• Up/Up = Bridge PU
• Up/Down = Both pickups
• Down/Down = Neck pickup
• Down/Up = Mute (standby)

In all cases both pickups have a resistor connected from hot to ground.

[stratomaster]

In parallel to the pots/signal path instead of in series with the pickups. Your post cleared it up. Thanks!