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Active to passive/active mod Jazz Bass


zvirus
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Hello Everyone,

I wonder if someone could help me.
Currently trying to change my Active ESP J4 bass into Active/Passive Bass.

It works perfect in Passive mode but in active the sound is weaker and 2 tone pots behaves strange (weak would say)
I have no idea how to disconect passive tone pot B250k in this case. Got this stage where Active pots and passive pot worked simultaneously in active mode.
Passive mode is always OK.

Please see attached simplified drawing for this mod:
[attachment=177211:SWITCH.jpg]

Thank You for any advice given.

Edited by zvirus
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Hi,

So far, I have removed the master tone 250k (passive) and sounds pretty good in active and surprisingly in passive mode even when I do not have tone control in passive mode.

Ones had GMR custom made Bass with MEC pickups and MEC 2 band preamp and I remember there was no tone control in passive mode but this time bass sounded pretty bad(!) in passive mode of course....

Cheers,
Tomas

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I'm just going to throw something into the mix here.

A few years ago, I installed a John East retro unit into a Jazz bass and experienced something similar to what you're describing. From memory I recall there was a couple of trim controls on the active unit to allow a bit of balance/parity between active/passive output - it was something as simple as adjusting a pair of tiny screws in the active part of the circuit. I know all these things are different...if it's working in both modes, perhaps you simply need to tweak the output settings (if there are some). Also, try a new battery!
P

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The battery has been checked and it is 9.45V.... there is no other regulation screws on preamp.

The problem was a loop in active mode with passive tone control. I have found simple solution: No Load Pot which disconnects the pot when reach the end of the pot...
This will allow me control the tone in passive mode and disconnect the loop in active mode.
I do not need another control tone in active mode and makes me happy!

here it is my updated mod wiring diagram:



works brilliant.


Cheers,
Tomas

Edited by zvirus
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