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Push-Pull Potentiometer Selection for Specific Electric Guitar Effects

argon

Apr 14, 2016
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Well, I've scoured the Internet--mostly guitar-related forums as well as pickup manufacturers--and still I cannot for the life of me figure out which type of pot I need for two different audio effect applications. As far as I can tell, there are four types: SPST, SPDT, DPST, DPDT

Here are the two modifications to a wiring harness I'd like to make:

1. Three-pickup guitar and all three pickups simply have two wires: one "hot" lead and a ground. Two of the pickups are connected to the same switch connection (neck and middle). Which type of pot would I use to engage the middle pickup optionally while maintaining constant connection of the neck pickup (regardless of whether the middle pickup being used or not)? I am assuming I can leave the constantly active neck pickup connection at the switch. I'm further assuming that the added second pickup (optionally on/off -- push-pull) would be connected directly to the pot terminals.

2. Optionally engage a small cap that would affect treble tone. The pickup output, again, would be constant, and the cap engaged at will via push-pull pot to affect the pickup's tone. I think the cap would be connected at two terminals of the pot (a double-pole variety?).

About the only application that is usually addressed on these other web sites is for splitting the two coils of a humbucker pickup. I can't find a "how to wire a DPDT (or other specific) pot" video or description; if I could find representative wiring examples with their respective applications for all four of these types of pot, I think I would be able to figure this out. But, I can't. The SPST seems to simply be an absolute on-off switch and would not allow any constant signal pass-through. I don't know about the others. Any suggestion welcome. Thanks.

PS - I removed a similarly-assembled harness that did not seem to work. Both effects were wired to the Volume pots, one effect per pot.
 

Alec_t

Jul 7, 2015
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I cannot for the life of me figure out which type of pot I need for two different audio effect applications. As far as I can tell, there are four types: SPST, SPDT, DPST, DPDT
'Pot ' is short for 'potentiometer, whereas 'SPST' etc are types of switches. Are you referring to plain switches, or to potentiometers incorporating switches?
 

Audioguru

Sep 24, 2016
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He wants an audio mixer on the guitar so that the pickup levels can be adjusted.
 

argon

Apr 14, 2016
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Sorry, I should have been more thorough from the start. I've attached photos with basic component ID. I've also linked the unmodified schematic. I need to re-phrase the goal/purpose of each of the two potentiometers.

1. As described: One pickup (neck location) always on, with optional off-on at will for the middle pickup. When off, only the neck pickup will be heard. When on, both pickups will be heard. (One or Both/Combined) (Pot shaft pushed "down" selects neck pickup. Shaft pulled "up" selects/combines both neck and middle pickups)

2. ERRONEOUS DESCRIPTION, ABOVE: In this situation, with the pot's switch "off"/down, the signal passes through without modification. With the pot's switch "on"/up and the capacitor now engaged, signal is "transferred" to/through the cap circuit only -- the cap is switched on, and the basic/first position/unmodified signal is entirely off. If both were to have closed circuits at the same time, there would be no change in tone, as the non-cap circuit would act like a shunt and negate any cap influence. (Either--Or) (Pot shaft pushed "down" selects input signal. Pot shaft pulled "up" transfers/moves the input signal to/through cap). This 0.0047 uF cap yields a very trebly result, that classic Rickenbacker "jangle" tone (think: The Byrds, e.g., their version of Bob Dylan's "Mr. Tambourine Man,).

Link to unmodified ("original" schematic): 19505.pdf (rickenbacker.com)
Many people disconnect the middle pickup (ala John Lennon), but some want an option to include it at will, hence, the push-pull pot option.

Photos: The first is the harness I removed; it would not work. While I know little about this stuff, it sure seems that the cap soldered to the volume pot is not connected correctly -- one lead appears to be connected to the "push" position/selection terminal, and the other lead of the cap to the "pull" position/selection of the pot's connection terminals....
IMG_4667.JPGIMG_4668.JPG IMG_4669.JPG

PS - Switch: original configuration has both the neck and middle pickups/inputs connected to one side of the switch, and the neck pickup/input to the other side of the switch. Toggle at middle position = all three pickups active
Toggle at up position = neck & middle pickups actively engaged (unless middle is purposely disconnected, as mentioned)
Toggle at down position = neck pickup only actively engaged

PPS - Having written all this, I believe the pots on the harness are DPDT, although they may not be the correct or optimal push-pull pots for my goals. I think I'm going to draw/diagram that harness out and maybe someone here can find the problem(s) with its wiring. This might take a day or two.
 
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Bluejets

Oct 5, 2014
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An actual circuit diagram would be the best approach at success as a long description usually results in some misunderstanding at least.
 

argon

Apr 14, 2016
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Yeah, long discussions can lead to error. I noticed that my describing the switch and its down position, it should have said, "selects the bridge pickup alone." (Too late to edit that post.)

Well, all I can do is assume that whoever made this harness that I removed at least had a basically correct idea of pot selection and use. The best I can do is present that as a diagram and we can see if there is a connection error or not. Perhaps instead of building an entirely new harness, I might be able to make some reconnections. I can't do it now -- I can't even identify/distinguish between the various push-pull pots available (hence, this thread), so I sure won't be able to wire one up correctly without advice.
 

argon

Apr 14, 2016
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Ah, yes I can. An accurate diagram would help. But if I only knew which type of push-pull pot would perform the functions I described, I can figure out the correct terminal connections, starting mainly with my multimeter and assess the character of the in & out connections.

The two pots on this harness are identical, even though they are enabling different functions. The only marking (identification) on the pots is the number 603. There is no mfr. info or anything else. The pot must be a DPDT I'm guessing. I think I'll buy a couple and investigate/experiment.
 

CircutScoper

Mar 29, 2022
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I have no idea what a push-pull-potentiometer might be, but I love the alliteration!
 

Alec_t

Jul 7, 2015
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It looks as though both push-pull pots have DPDT switches, but one pole of the switch on the pot without the capacitor is unused (so effectively it is a SPDT switch).
 

argon

Apr 14, 2016
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Martaine2005: Yes, that looks like the typical push-pull pot used on guitars. If you read through the Amazon description of that example you linked, you will NOT find any information regarding the specific type/design of that potentiometer. This is what has been frustrating during my quest to distinguish pot types.

Alec_t: I'm still too inexperienced to tell, but it occurred to me today that one pot--the pot with the cap--has to be wired in an "either/or" configuration (circuit A --or-- circuit B selections), and the pot is likely designed to work in that fashion (two variations, each optionally engaged singularly/separately). Since the other identical pot is used for the Addition of the middle pickup, there must be a shunt installed at that pushed/down switch position that also continually passes through the signal, so that, say, for example, when the pot is in its pulled (up) position (secondary/alternate) there still remains a signal pass-through connection (the same effect that would normally be engaged in the pushed (down) position).
(circuit A --or-- circuit A + B selections)

I'm going to get a DPDT and experiment with the continuity of various connection terminals with "pushed" vs. "pull" with my multimeter. I do not want to remove the pots from the existing, old harness. It will be interesting.

Thanks, all!
 

Martaine2005

May 12, 2015
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It looks like a DPDT on a 500kΩ pot.
You can measure your pots with your multimeter. Measure the two outside terminals for the Max resistance.


Martin
 

Martaine2005

May 12, 2015
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pushed" vs. "pull" with my multimeter.
That will switch from centre common to left side of switch and centre common to right hand side of switch. The DPDT has two of these for two different circuits to be switched. For example, push will switch centre and left side while pull will switch centre and right side. But you can also wire the switch other ways too.


Martin
 

argon

Apr 14, 2016
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Martin - I'm glad you prompted me to measure the pots. I assumed that they were installed per specification (and it seems they were), as noted on the schematic (above link). That is, they should (if originality is a goal) be: 500k tone pots (the plain vanilla, regular ones) and 250k volume pots (the ones that were exchanged for the push-pull). The tone pots are easily identified because the basic tone caps come off the switch and go directly to their respective control pots. The volume pots are the ones that have been replaced with the push-pull versions.

My "250k" tone pots measure 206k and 210k. The "500k" volume (push-pull) pots both measure about 244k.

(FYI: Treble tone and volume designations, and Bass tone and volume designations indirectly refer to pickup locations on the guitar body; strings behave and sound differently at different locations along the strings. Near the "top" of the guitar body, close to the neck attachment to the guitar is where the "bass" or neck pickup is located. Near the bottom of the guitar, near the bridge (supports the strings and establishes string length/pitch at this end of the strings) is where the "treble" or bridge pickup is located.)

I'll get a couple of DPDTs that are known to be used in guitars -- the vertical distance from the underside of the pickguard to the bottom of the cavity in which the electronics protrude is limited. These push-pull pots seem to be pretty accurate, and if I can identify the manufacturer of these, I'll buy those; I already know they will fit. I'll look for something with a tighter tolerance for the tone pots (Bourns, perhaps).

Thanks.
 

argon

Apr 14, 2016
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It's been a while I thought I'd update things. I did a lot more investigation on the Internet. Bourns make a series of audio/guitar potentiometers: Bourns® Professional Audio | Guitar Potentiometers & More
I ended up with this: PDB183-GTR 17 mm Guitar Potentiometer w/Push-Pull Switch (bourns.com) which is appropriate for my simple pickups with only two wires (hot/signal and ground); there are more sophisticated types for humbuckers (dual single coil pickups) with five wires.... I did goof up my order by mixing up the resistance values of the pots I ordered. Instead of 250k volume DPDT I mistakenly ordered 500k. Instead of 500k regular/typical pots I ordered 250... got confused and reversed things. After receiving the DPDTs, in spite of careful estimation, I can see that they are probably going to be too long for my solid body (relatively thin with routing for pots and switch); intended for a thicker hollow body guitar. The pot and switch portion should fit within the available routed depth, but I did not pay attention to how long the threaded sleeve was; the end of this sleeve, once secured with a nut, should be close to the surface of the pickguard or else the control knobs are going to be very high above the surface of the pickguard. Minimizing this sleeve protrusion will certainly "make" the overall length too long to fit within the available depth of routing. This style of DPDT pot, however, seems to have lost favor among the guitar crowd, as CTS has a different style and overall superior DPDT assembly (shorter overall and 24mm pot). Next time I'll order these:
CTS Push-pull Pots, DPDT - StewMac
Wiring the CTS DPDT Push-Pull Pot - StewMac

Anyway, I'm going to experiment with what I have. It took a while to understand exactly how these DPDT pots worked. Once I understood that there are three functional components to a DPDT/pot assembly it was just a matter of figuring out the wiring schemes needed to accomplish a respective goal. Here's a series of worksheets I used to wade through this:
Conceptual view.jpg Overview of goals.jpg Worksheet for middlle pickup option.jpg Worksheet for tone cap option.jpg

I wanted to make a breadboard but needed something practical. I decided on a plastic storage box, something that would give underside depth for the control shafts of the pots (cutouts for my hands to reach underneath and make adjustments. The pots are "upside-down" as would be the case if I were working on the electronics with the populated pickguard flipped over:
Guitar Breadboard.JPG Breadboard with pots wired.JPG Bridge volume DPDT wired.JPG

So, that's it so far. I have continuity at all points tested. I used nearly-dead batteries as my pickups, and as far as I can tell the switching is working correctly. I used my multimeter as the "amplifier" to monitor changes as I manipulated the switches & pots.

I'm going to assemble all components of an electric guitar on this breadboard and use long leads to connect to my guitar's pickups (disconnect and bypass the guitar's inherent electronics); I'll include a jack so that I can connect an amp. It should be fun. Once I finish fooling around with this, I suspect I may just stop and not make a new harness after all. It's just so cool to see if you can do something like this, and know that you can if you change your mind.
 

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Audioguru

Sep 24, 2016
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The pots have one of 3 "tapers".
The schematic does not show the taper needed for volume or tone and your pot part number also does not show the taper number (A, BO or C2) that you ordered.
 

argon

Apr 14, 2016
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The pots have one of 3 "tapers".
The schematic does not show the taper needed for volume or tone and your pot part number also does not show the taper number (A, BO or C2) that you ordered.
In the lower right corner of the first page of the data sheet is a guide, "How to Order." I ordered the A2 Audio taper. After going through and determining my order code, I went to Mouser ; no problem to find the pot and order.
 
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Audioguru

Sep 24, 2016
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Normal volume controls are connected as voltage dividers with the slider as the output feeding the amplifier input then A2 taper is used.
The Rickenbaker wiring is backwards with the sliders shorting the input signals then I think the C2 taper is used and maybe also for the tone controls.
 

argon

Apr 14, 2016
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I've never seen/read mention of a C2 taper for guitar use, although that's just my experience. Mouser has a great selection of everything; I thought I'd get an A3 taper pot, but that one was not available; A2 is fine. Yeah, Rickenbacker is in a league of their own when it comes to doing things.....

Anyway, on my breadboard I've added the tone pots, pickup selector switch and output jack. It looks really messy, but I will be changing the wiring with customized lengths. I just today receive some 22 gauge two-connector wires to clean up the connections to the guitar, and have ordered more of those 20-in. test leads so I can cut a few up, have consistent colors for respective functions/connections.

I think I'll do some more of this stuff. I have a bunch of Alpha (mfr.) pots and I'll experiment with different resistances before buying CTS "regular" and their newer DPDT pots for a new harness to be installed in the guitar. It's going to be fun.
 

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