Pick Up Phase Switch

[MichaelStewart]

When I changed the hi-gain pickup to a toaster on my '79 4001, I accidentally wired it out of phase.

(I had previously installed the "vintage tone circuit" and I love the variety of sound possibilities that modification brings)

One thing I had noticed right away was that the pickups were louder when they were individually selected. This is what tipped me off that they were "out-of-phase".

But while in the middle position, I noticed a somewhat different sound capability the 4001 did not have after I re-wired it correctly. Since I like getting different sounds from my bass without necessarily using external effects, I decided that I wanted to be able to switch between 'in-phase" and "out-of-phase", but I did not want to change the "look" by adding another switch.

Is it possible to replace the tone potentiometer on the neck pickup with a push-pull potentiometer, (similar to the one I used for the "vintage tone circuit"), and wire it to be "in-phase" or "out-of-phase", depending on the position of the switch?

If so, I would be "much obliged" if someone would provide a drawing showing how the new arrangement would look. I am somewhat "schematic impaired" but yet handy with a soldering iron. Also, what value should the potentiometer be?

Thanks in advance!

[cassius987]

The cone filtering mine does in the middle position is already drastic enough of a difference for me!

[cjj]

Is it possible to replace the tone potentiometer on the neck pickup with a push-pull potentiometer, (similar to the one I used for the "vintage tone circuit"), and wire it to be "in-phase" or "out-of-phase", depending on the position of the switch?

If so, I would be "much obliged" if someone would provide a drawing showing how the new arrangement would look. I am somewhat "schematic impaired" but yet handy with a soldering iron. Also, what value should the potentiometer be?

Thanks in advance!

Sure. The value of the pot should be the same as the one you replace. I believe the switches on most of these pots are what's called DPDT, double pole double throw, which means they are really 2 switches side by side that can connect 2 ways. So, a diagram:

Phase reversal switch

Well, that's not too great, but, you just run wires crossed from each end of the switch to the other end. Hook the pickup to one end, and hook the output to the rest of the circuitry to the center 2 pins of the switch.

[nukebass]

This may be a stupid question, but what exactly is "out of phase" from a pickup point of view? I played one of the Brian May guitars that has phase switching and really liked the out of phase brightness, but have no idea what that really means.

[cjj]

This may be a stupid question, but what exactly is "out of phase" from a pickup point of view? I played one of the Brian May guitars that has phase switching and really liked the out of phase brightness, but have no idea what that really means.

The only stupid questions are the ones you don't ask!
OK, this is probably easier to show with pictures, but I don't have any off hand, so, I'll give it a go with words. In or out of phase has to do with the relationship between two different waveforms. Let's say that a guitar pickup puts out only one tone, or frequency, say, 1kHz, or 1000 cycles per second. This will be an alternating waveform, going positive and negative such that it goes positive 1000 times per second. Does that make sense?

OK, lets get another pickup doing the same thing. If we hook up the wires in exactly the same way, each pickup will be putting out the same wave, going positive at the same time then negative at the same time. This is called "in phase". Now, if we were to reverse the wires coming from one pickup, its output wave would be going negative when the other pickup's wave goes positive. This is "out of phase".

If the exact same signal is coming from each pickup and you connect them out of phase, the signals will cancel each other out! When one goes positive, the other goes negative and when added together, you get zero. This, by the way, is kind of what humbucking pickups do to cancel out hum. If they are in phase, the signals will add and you get a louder output.

Now in the real world, on a guitar, the pickups are placed at different locations along the string and may be of different designs. This means that the signals from each one will never be quite the same, and they always have more than just one frequency. So, when connected in phase, certain portions of the different signals will add together and be louder, while other parts will not add and just go on their merry way. When out of phase, certain portions will cancel and others don't, giving a different sound than the in phase sound.

Now, the reason the out of phase probably sounded brighter is that the lower frequencies are probably getting canceled more than higher ones since they are closer to the same from each pickup. That's a huge oversimplification of what's going on, but it's basically the idea.

[MichaelStewart]

Thanks CJ!

I really appreciate the prompt reply... and easy to understand too.

One more question though concerning the value of the potentiometers.

When I installed the "vintage tone circuit" I was advised that I should buy a "POTENTIOMETER 500K W/DPDT SWITCH" from the Ric boutique, which I did. I wondered why I would replace a 330k with a 500k, but that was what they had for sale on the Ric site, so I went ahead assuming that was correct for the "vintage tone circuit".

How does the value of the tone potentiometers effect the overall tone? Should I use 330k pots with dpdt switches on both the "vintage tone circuit" and the "phase switch"? If so can you recommend where I might find two?

Thanks again!

[cjj]

The pot in the tone circuit adjusts the cutoff frequency of a filter circuit. The way the pot is wired into the circuit on a 4003 is such that it really shouldn't matter whether you have a 330k or a 500k. Basically, the pot is between the 0.047uF cap and ground, and can be thought of as varying the amount of high frequencies that get shorted to ground (it's more complicated than that, but it's easy to think of it this way).

Now, if you have a 500k pot, you can adjust it part way through its range and at some point it will have a value of 330k. From that point on down to zero, it will be just the same as if you had a 330k pot in there. The difference is that you can also go up in value above the 330k point. This will allow more high frequencies to be sent to your amp, giving you the ability to get a bit brighter tone than with a 330k.

If you want a 330k pot with a switch, you can probably find one at one of these places:
http://digikey.com/
http://newark.com/

[johnallg]

The 4001 and early 4003 models had 500k tone pots. The there was a long stretch of 250k tone pots. Recently (last couple years?) the value was changed to the current 330k. If you already have a vintage tone circuit in, change out the other tone pot with a RIC one and both will be the 500k value, just like the old instruments. Besides, there is not much difference from 330k to 500k to the ear anyway.

[rickysyurbass]

Hi folks, its been a wee while.

I installed a MusicMan active circuit from my Sabre bass around 1986-87 into my 1985 4003 and I also wired the centered position on the PUP selector switch to put both PUP's out of phase, and the sound I got was pretty good, I thought.

It was very much like the sound that Geddy was getting on the Power Windows album at the time from his Wal, kinda nasal, but punchy and was a very worth while experiment, maybe he should've done this to his 4001 and stuck with the Ricks and saved a few bob at the same time.

Just thought I'd share that wee bit of info with you all.

TTFN

[cassius987]

I believe the switches on most of these pots are what's called DPDT, double pole double throw, which means they are really 2 switches side by side that can connect 2 ways. So, a diagram:

switch.JPG

Well, that's not too great, but, you just run wires crossed from each end of the switch to the other end. Hook the pickup to one end, and hook the output to the rest of the circuitry to the center 2 pins of the switch.

So this is basically just reversing the which wire goes to ground, or...? I mean, there are only two wires to work with that I know of, hot and ground, for most RIC pickups.

I was reading the Guitar Player's Repair Guide (have had a copy for a decade, only just now beginning to understand most of it) and it was discussing using a DPDT switch similarly to do fun things to humbuckers. Whenever I get my 4003 MG that I reserved in Feb. 2007 (for what now seems like pennies) I am really debating putting my HB1s in and trying some of them out. For instance, parallel out-of-phase vs. series out-of-phase switching, or parallel out-of-phase to parallel in-phase.

[cjj]

So this is basically just reversing the which wire goes to ground, or...? I mean, there are only two wires to work with that I know of, hot and ground, for most RIC pickups.

Yes, that's pretty much it. It's swapping both wires so the one that used to go to ground now goes to the rest of the circuit, and the one that used to go to the circuitry now goes to ground.

I was reading the Guitar Player's Repair Guide (have had a copy for a decade, only just now beginning to understand most of it) and it was discussing using a DPDT switch similarly to do fun things to humbuckers. Whenever I get my 4003 MG that I reserved in Feb. 2007 (for what now seems like pennies) I am really debating putting my HB1s in and trying some of them out. For instance, parallel out-of-phase vs. series out-of-phase switching, or parallel out-of-phase to parallel in-phase.

Hey, I've got a 4003MG on order too, reserved March 2007! I've got a hunch we'll both be getting our new basses at about the same time! Interesting idea on playing with pickups and phase switching, I was just going to modify mine to be a 5 string, but I may think about some switching now too.

[cassius987]

Hey, I've got a 4003MG on order too, reserved March 2007! I've got a hunch we'll both be getting our new basses at about the same time! Interesting idea on playing with pickups and phase switching, I was just going to modify mine to be a 5 string, but I may think about some switching now too.

Sweet! Let me know what you do.