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How Do I Bypass An Active Circuit Thats Always On?


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ok i have an EMG ABQ from their laiho signature pickup in my guitar. The gain boost can be switched on an off but the frequency boost is always on.

there is only one volume knob in my guitar and the ABQ is it. and there is an empty hole where the tone used to be.

i have a push pull pot i just bought. i cant use those flip switches because i dont want to dril another hole. http://www.musiciansfriend.com/accessories/dimarzio-500k-push-pull-pot/987357000000000?src=3WFRWXX&ZYXSEM=0&CAWELAID=26057910

how do i wire these the ABQ with the push pull so that when i pull it, the ABQ is bypassed and the signal goes straight to the jack? (pushed in will be "on" mode)

please help me out!


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Look up a diagram for "true bypass" wiring. This will be just like wiring up a stomp box with true bypass, where the ABQ is your effect.

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That would probably work fine, though I am not responsible if it blows up :D (by the way, that is nigh unto impossible).

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I'm doing this very thing on an Aria Pro II RSB-600 restoration with retrofitted a SB-1000 style active circuit. The active part is bypassed by a 3PDT switch and the pots are dual gang with 20k on one with 250k on the other to allow appropriate impedances for passive and active modes.

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ok i just put in the dpdt but i noticed some tonal differences even when the active circuitry is bypassed.

when on bypass mode, i took the battery out and the guitar sounds warmer. still bypassed, i put the battery back in and the tone is more sparkly, but less warm. its not a big difference but it still is different.

is it supposed to sound 100% like the pickup when bypassed or is the bypassed active circuitry always gonna color the tone?

i used this http://generalguitar...t_input_grd.gif

the only thing i changed is 1 wire from that diagram.

instead of the ground from the top left pin to the board ground...

i put the ground from the top left pin straight to the output jack ground.

or, do you guys think its a buffer that might be in the active circuitry thats coloring it?

Edited by esppse
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It sounds like there is a load attached to your passive circuit. What is the input impedance of your active circuit? My hybrid is a true mechanical bypass (hence needing 3PDT, not 2PDT) so I suspect that the input of your active circuit could be the issue.

im not sure how to find the exact impedance of the circuit, i have a multimeter but i am not to experienced with it. can you help me with what to put the multimeter dial on and where the 2 meter pins go?

however, i do know the circuit is a low impedance active circuit.

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I am not entirely sure if you can measure the input impedance of a circuit using a multimeter. Without a circuit diagram it may be difficult to ascertain. Essentially you need to bypass the active circuit completely, cutting the connection between the passive circuit and the input of the active circuit, thereby removing any load the input of the active circuit is "draining" your passive components with.

Check this circuit out and let me know if you can see how it works. If not, then I will explain. Not entirely easy to do right now having beered myself up somewhat:


You want to be examining the fourth diagram labelled "New SB1000". The pots are dual gang with 20k and 200k wafers each. The 20k are for the active circuit and the 200k for the passive (I think it is 200k anyway). The pickup part is redirected from the input to the active circuit and the passive circuit rather than being shared. The same applies to the output of the active circuit and the passive circuit. A real physical bypass. :D

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oh wow, thats a quite a confusing circuit. i examined it but that cant really be done with 1 DPDT right? thats all the room i have in this tiny electronics cavity for since the 9v is takes up quite some space and only 1 hole left for the pot. :D


instead of this diagram i used


do you think trying this would have any effect?


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Either should work really. The first one is only useful if the circuit you are switching out is noisy, however both are adequate. You're right in that the Aria circuit is a little confusing....I forgot that it involves a split 18v supply....sorry! I wasn't really thinking and rushed the post.

A true bypass as Ripthorn recommended is your best bet.

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