Automatic on/off switch for Active electronics

[mainechuck]

I play a variety of instruments through a looper, and have a large pedal board set up with a master on/off for keys, handsonic, amp, effects and so forth. The only thing not on the master is the bass's active electronics. My bass spends most of its time on a stand, being picked up for use once or twice for each tune. So I figured I'd put a tilt switch inline with the battery, with it open while the bass is in the stand, and closed when in a playable position.

It works great! No more dead batteries when I forget to unplug the cord!

The only drawback is that when I pick up the bass I get a pop similar to that heard when plugging in the cord. Turning down the volume solves the issue, but I'm curious if anyone has any ideas on how to gate the output so that this is not an issue. Suggestions?

Chuck

[Jazz P Bass]

So the question is really, "why does the active preamp pop when you activate the circuit?".
You could maybe try a small value capacitor across the battery switch.
Or maybe a 2 pole, 3 way switch would work.
Off, activate 9 volts, activate output (and 9 volts)
Other than that, you are talking major surgery on the preamp circuit.
Or you could buy a gate pedal & engage it when you turn on the preamp.

[mainechuck]

Not enough real estate

I like the 2 stage switch idea, but there's not enough space in the cavity to fit a second tilt switch. The capacitor idea's worth a try, so I guess I'm adding that to the future projects list. Thanks for the feedback!

[Jazz P Bass]

Or you could wire up a transistor (jfet) that, when turned on, passes the output of the preamp.
Then you could use an RC circuit to ramp up & turn the base (gate) of the transistor (jfet) on "after" the pop from the battery being turned on.

[mainechuck]

Part suggestions?

Sounds like another possible solution. I haven't spec'd components in ages, would you have any suggestions?

Many thanks for your wonderful input!!!

[David Schwab]

So the question is really, "why does the active preamp pop when you activate the circuit?".

Same reason any solid state amplifier pops when you power it up or down. It's the transient spike of the power going through the circuit.

I'm surprised there would even be a need for this. I often leave my active basses plugged in on the stand at home for a week, and my battery last at least 6 months to a year.

[mainechuck]

I only get out about once a month... so the bass is on the stand most of the time. Only have the problem once or so a year, but plugging in/out over and over again is pain so thus the tilt switch idea....

[David Schwab]

I only get out about once a month... so the bass is on the stand most of the time. Only have the problem once or so a year, but plugging in/out over and over again is pain so thus the tilt switch idea....

There's no need to unplug it during a gig. Just unplug it at home when you aren't using it.

[mainechuck]

"There's no need to unplug it during a gig. Just unplug it at home when you aren't using it."

That's the issue... I'll play for 15 minutes a couple times a day, 5-6 days a week... 30 times a month to forget to unplug it...

[Jazz P Bass]

Seat of the pants, back of the envelope sketch.

[Steve Conner]

JPB, that won't work because transistors only conduct in one direction. They won't pass audio without distortion.

If you're using the transistor to bring up the 9V supply slowly, I still don't see how it's going to work.

This is one of these things that looks simple, but in actual fact is more hassle than just remembering to take the plug out of your active bass when not using it.

[Jazz P Bass]

Thanks for the clarification Steve.
That was certainly a DUH moment.

[mainechuck]

This is one of these things that looks simple, but in actual fact is more hassle than just remembering to take the plug out of your active bass when not using it.

In my case it is simply turning down the volume when I put the bass back on the rack... which I think is the best solution for now.

Thanks for all the support!

[David Schwab]

"There's no need to unplug it during a gig. Just unplug it at home when you aren't using it."

That's the issue... I'll play for 15 minutes a couple times a day, 5-6 days a week... 30 times a month to forget to unplug it...

Well you remember to turn off your car and take the keys with you right? It's not a hard habit to get into.

If you want to do it by turning down the volume knob, get one with a switch. Turn it all the way down and it will turn off the battery.

But... you have to remember to turn down the volume. if you can remember that, you can unplug it.

[Steve A.]

I play a variety of instruments through a looper, and have a large pedal board set up with a master on/off for keys, handsonic, amp, effects and so forth. The only thing not on the master is the bass's active electronics. My bass spends most of its time on a stand, being picked up for use once or twice for each tune. So I figured I'd put a tilt switch inline with the battery, with it open while the bass is in the stand, and closed when in a playable position.

Hmmm... I don't believe that would work very well for Bill Wyman. If you are as clumsy as me leaving a cable plugged into a guitar or bass is asking for trouble. I'll be walking by and snag the cable with my foot- the next thing you know... Timber!

IMO a phone jack is basically self-cleaning; inserting and removing a plug keeps the contacts clean. I also think that leaving the plug in all of the time can weaken the metal in a cheaper imported plug (I have never seen that problem with a Switchcraft jack.)

Steve Ahola

P.S. I recommend that anyone who uses batteries in guitars, basses or stomp boxes get the Keith McMillen Batt-O-Meter which will measure the voltage of a 9v battery without removing it from the circuit and judging by the current draw will give you an estimate of how many hours are remaining. Circuits like an active bass will typically give a reading of 999 (which is as high as the display goes).