Jerry C

I built myself this little gadget a while ago to end battery anxiety once and for all:

Don't do it. USB-rechargeables have built-in electronics that make a lot of audio-band noise. A decent onboard bass preamp should last at least some months, if not a year or so, on a good battery if you turn it off when not playing. An alkaline 9V battery has a capacity of some 500mAh and a decent preamp should draw no more than 1 or 2 mA. That's hundreds of hours of play time.

Use a compressor. Makes a huge difference.

In the unlikely event that someone is interested, I make a headphone amp designed to go onboard a bass. It even has a stereo Aux In to play along stuff: https://www.jtex.ca/products/headamp I also make an onboard compressor (!) that can directly drive headphones to a decent practice level (unofficially): https://www.jtex.ca/products/okc I'm in Canada, but currently offer free international shipping as a middle finger to the USA tariffs (I don't ship there anymore).

Try inserting a 0.1uF box cap (film) just before the top lug of the volume pot (see atached). You don't need much more than 0.1uF since it feeds into a high Z 500k pot.

The capacitor that's leaking would be on your active preamp board, ahead of the putput volume pot. Can you attach a pic of the preamp?

I do make a multifunction buffer/booster contraption with user-configurable input Z (via DIP switches) that hardly anybody knows about because I hate marketing. You might want to give it a look: https://www.jtex.ca/products/bmb

Yes, it works with just about any pickups and can (and should) be calibrated to suit the pickups' output level. The hardest challenge was making it have a long-enough battery life, since there's a lot more going on than in a typical onboard EQ, for example. I managed to get 350 hours of play out of it. Oh, and it has a worst-kept secret feature: it can drive headphones.

I don't often wander on this side of the pond, but I did just now and somehow stumbled upon this thread. In case anyone is still interested, I did just brew a new batch of my onboard one-knob compressor: jtex.ca/products/okc I honestly think it really whips the Llama's arse! Too bad very few people think of a compressor as something to put onboard.

When you reduce the volume, a part of the volume pot's resistance (from top to the wiper) gets added in series with the pickups, effectively increasing the instrument's output impedance. A higher output impedance does a poorer job of shorting out any noise picked up by the cable, so it makes its way to the amp. Try a different, or maybe just shorter cable. It might have better shielding, picking up less noise. The better solution is, I'm afraid, an active bass - or activating yours. Active electronics have low ouput impedance and are not significantly affected by long and/or not so great cables.

I designed a circuit specifically to once and for all remove battery status anxiety from my life. I use it in every battery-powered instrument I own. You might want to check it out at http://jtex.ca/indicator While it's normally designed for 9V systems, I can easily mod it for 18V by request.

If you're not averse to the idea of installing a compressor onboard, like an EQ, then might I be so bold as to suggest the One-Knob compressor that I make: jtex.ca/okc I think it really whips the Llama's arse, but I might be biased, so don't just listen to me. If it must be in a pedal format, you can easily mount it in a stomp box yourself. Just needs the I/O jacks.

I've put basses on an oscilloscope and some can easily have transient peaks as high as 2V when played hard. Yes, the average level tends to be in the hundreds of mV, but they're very peaky. Having said that, I've never felt that 18V was necessary. One can always use rail-to-rail op amps that can make full use of the 9V supply. That ought to be enough headroom for anything I can think of in an electric guitar/bass.

Dear people who care about bass effects, I haven't visited here in a while, since I live on the wrong side of the pond, in TalkBass land. I'm happy to report that I managed to put together a one-knob compressor that I consider worthy of installing onboard a bass and thus becoming part of its sound. It's a miniature, 9V battery-powered offspring of the classic dbx 163 "Over Easy" one-slider half-rack compressor. I just thought I should inform the other five bassists on the planet who think an onboard compressor is a good idea 😊 Just for you, here's where you can find out more: jtex.ca/okc From frozen Canada with love, Jerry

You wouldn't forget to unplug the cable if you had something like this to remind you that the bass is on. And no, I'm not offering them anymore, due to general apathy JTEX Indicator Demo - YouTube