Squier deluxe Passive Switch

Discussion in 'Pickups & Electronics [BG]' started by heavyfunkmachin, Oct 23, 2013.


  1. heavyfunkmachin

    heavyfunkmachin

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    I'm a fearful fella... And while enjoying my Squier deluxe jazz V I'm afraid to be let down by the batterie. So I want to have a "passive switch", in case all goes wrong.

    Is this doable?
    HOW?

    If someone can read the diagram and help me out it would be much apreciated!!

    This is the wiring diagram I found:

    [​IMG]
     
  2. gregmon79

    gregmon79 Supporting Member

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    I always wanted to do this with my Squier P becasue I have EMG's in it and thought it would be really cool to go passive if I so desired. Thanks for starting the thread! Sorry, but I cant be of assistance, I know how to wire up some pups but this is a tad advanced for me too.
     
  3. heavyfunkmachin

    heavyfunkmachin

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    will connecting the pink cable from the balance pot to a switch so it goes straight to the jack or back to the preamp work?

    :help:
     
  4. evermelon

    evermelon Previously srvlives4evr Supporting Member

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    I think you are on the right track. I just did a passive/active mod on my bass yesterday so the idea is still fresh, I made this up showing only need info and I believe it'll work. Should be simple, just a little re-working of wires but nothing to bad.
     

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  6. line6man

    line6man

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    This is a bad idea, because you are not disconnecting the signal from the preamp input, in passive mode, and that causes a decrease in input impedance on the pickups, which reduces output/treble.

    The proper way to do active/passive switching is to switch both the input and output, like this:
    [​IMG]
     
  7. evermelon

    evermelon Previously srvlives4evr Supporting Member

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    Ok cool. I thought there would be issues because of the 25k vol pot, and that the signal goes into the pre first. I will use this and redo. The signal from the blend is going into the vol input correct? Sorry for bad info:bag:
     
  8. line6man

    line6man

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    You can't use a 25k pot if you want it to function in both modes. Remember that the preamp buffers the signal, and that lowers its output impedance. The output impedance of the pickups is much too high to be controlled by a 25k pot, so the result would be a severe loss of output. You will want a 250k or 500k pot, right after the blend pot. Any time there is an active/passive switch, with high impedance pickups, the volume pot must go before the preamp input, so that the signal impedance will not change as the preamp is bypassed.
     
  9. heavyfunkmachin

    heavyfunkmachin

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    If i don't use any volume pot in passive mode, would it be ok to use your diagram chaging "out from volume pot" for " out from balance pot"?
     
  10. line6man

    line6man

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    No, you need to either get rid of the low-value volume pot, or wire the active/passive switch to take the preamp's signal from after the volume pot.
     
  11. heavyfunkmachin

    heavyfunkmachin

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    i still want to use the volume pot for the "active mode" on the bass... I only want this switch as an "emergency" measure where I can flip it and still have sound....How do you recommend the wiring?
     
  12. line6man

    line6man

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    The standard method is to simply use a 250k or 500k volume right after the blend pot. That way the pot controls the same impedance signal, whether you use the preamp or not.

    If you still want the low-value pot for active mode, however, there is always the option to put it after the preamp, but before the switch. That will allow volume control in active mode, but there will be no effect (i.e. full-volume only) in passive mode.
     
  13. heavyfunkmachin

    heavyfunkmachin

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    [If you still want the low-value pot for active mode, however, there is always the option to put it after the preamp, but before the switch. That will allow volume control in active mode, but there will be no effect (i.e. full-volume only) in passive mode.[/QUOTE]

    I have NO IDEA about how to wire this :help:
     
  14. khutch

    khutch Praise Harp Supporting Member

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    This is how Fender does it in the Reggie Hamilton:

    [​IMG]

    The top diagram shows how you could do it with a volume control. You would have to change the pot for the volume to a 250k to avoid loading the pickups too much. A 250k pot should work with the preamp although you lose its low output impedance. The bottom diagram shows a limp-home approach with no volume control. If you remember to change batteries once a year the limp home mode is fine because you will never use it!
     
  15. line6man

    line6man

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    In any practical application, that diagram is nonsense. The output impedance of most preamps is much lower than what would be desired for proper operation with a 250k volume pot, and thus, the volume pot is likely to behave as an on/off switch, with little range of control. This is because rolling down just a little bit will produce a very large resistance in series with the signal path, relative to the signal impedance, so the volume will drop off very early in the rotation.

    I'll post a proper diagram later.
     
  16. khutch

    khutch Praise Harp Supporting Member

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    Actually driving a 250k volume control from a low impedance will not affect its operation much at all. Passive basses use them all the time and the low output impedance of the op amp will just make it work a little better, not worse. The problems you describe would occur if you were trying to use the volume pot with a low impedance load. If you are intending to drive the normal 1Meg amplifier input impedance then a 250k volume pot will work just fine whether it is driven directly from the bass pickups or an opamp. If you intended to drive a low impedance load, headphones for example, then a 250k pot will not work well no matter what you drive it with. The effect you describe is real but it is caused by the load impedance, not the driving point impedance. The signal impedance is 1Meg in this case whereas the maximum series impedance the pot could introduce is 250k or a relatively small one quarter of the signal impedance.

    In any event the second (bottom) approach does not have a volume control at all in passive mode and the active mode is unchanged from stock. It would be perfectly acceptable as a limp home mode and it is a very simple mod.

    Oh, if anyone really cares the Reggie Hamilton circuit is not exactly like either one of those but it is more like the bottom one with one addition. Instead of passing straight through to the output the passive mode runs through a 250k volume pot that is ganged with the 25k active mode volume pot on the same shaft so that one knob controls both the active and passive volume settings. It is a nice approach but of course finding a two section 25k/250k pot for DIY mods is a little difficult. Some guitar parts places claim to sell "Reggie Hamilton" volume pots but I have never tried to order one so I don't know if anyone really stocks them. The complete Reggie Hamilton circuit is shown below.

    [​IMG]
     
  17. line6man

    line6man

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    I've never heard of anyone using 250k pots after preamps. (Unless the preamps have higher output impedances.) You always see lower values like 25k or 50k, because they are more appropriate to the signal impedance, to give you a good taper.

    In any case, this is the standard way to wire an active/passive switch with a volume pot that sees the same impedance in both modes.

    [​IMG]
     
  18. khutch

    khutch Praise Harp Supporting Member

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    The only real advantage to using a 25k pot after a preamp is that it gives the system a lower output impedance. As you know this is an advantage when it comes to driving cable capacitance. The "signal impedance" looking into the output of the opamp is probably under an Ohm. The open loop output impedance of the opamp is probably spec'd higher than that but it is inside a feedback loop in most opamp circuits and the feedback produces a very low output impedance. So neither 25k nor 250k are much of a load for the opamp to drive and one is as "appropriate" as the other as far as it is concerned. A 25k pot will drive a 1Meg load slightly better than a 250k pot but people don't complain about the latter in passive basses and the bi-linear "audio" taper used in all volume pots is such a horrid approximation of a true audio taper that people apparently are not bothered by fairly substantial variations from the ideal.

    The circuit you give certainly works although by putting the volume control in front of the preamp it will require the OP to do more work to implement it. Fender must feel that there is an advantage of some kind to putting the volume pot after the preamp, perhaps it is noise. The low current opamps used in active basses have relatively poor noise performance as it is and putting loss before gain makes noise even worse. Any time noise is an issue you put gain before loss. But any of the three circuits will work, the OP can make his own choice.
     
  19. PilbaraBass

    PilbaraBass

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    I replaced the preamp on my Squier Deluxe V with a Glockenklang 2-band. The vol knob is push/pull for active/passive. The treble control has a passive roll-off feature.

    I used the "slap switch" hole for a series/parallel switch, which I use often on rock tunes to put a bit of "oomph" into it.

    I'm very happy with the results.
     
  20. lokikallas

    lokikallas Supporting Member

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    I replaced the "slap" switch on mine with a passive switch. I bought the aguilar obp-3 pre from bestbassgear.com and it comes pre wired for a V,Bl,stacked treble/bass,mid and passive switch. Works great, sounds great, passive mode bypasses all tone controls. I use the bypass mostly to save battery, but it sounds exactly the same passive as it does with tone controls flat.
     

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