elros

Got it. Brief description: The jack connects the negative lead from the battery to ground, thus competing the avtice circuit. The transistor does the same thing when it recieves the -7V from the GK circuit. So you can leave the 13-pin plugged in, and just turn off the GK unit it is plugged into. This will deactivate the on-board electonics - provided there's no jack plugged in. Makes sense?

Hi, Yes that's how it is these days. For some reason the guitar version of the GK pickup electronics has a built-in function for switching on the on-board electronics when the GK cable is connected, but the bass version has no such thing. Go figure. Anyway it is possible to build such a circuit on a DIY basis. All you need is a transistor (PNP bipolar IIRC) and a resistor (Rb anywhere from about 4k7 to 100k). I think I had a schematic somewhere... Until I find it, a dummy jack is a good solution.

Sorry I'm late for the party. You've got it right, obviously, but there's one little detail: since your bass circuit is active and switched by the output jack, it won't be on if you use only the GK cable. For you it isn't a big problem, because as far as I can tell from your schematic you've got a passive mode. On my installation I made a little circuit that switches on the active electronics when power arrives from the GK cable.

The single-stage FET buffer is very easy to throw up. And it would easily fit inside pretty much any control cavity. I'll try to remember snapping some photos of mine next time I'm able. Should be in about ten days.

An active on-board buffer is the best solution. A seperate output could work, but it's quite possible that you'd lose low end due to the longer cable run. After all, the piezo pickup is a capacitive source.

And the buffer is needed for impedance matching only - the levels are often very close to the magnetics (there's a lot of variation between different magnetic pickups, you know). For my Warmoth build I used a simple one-stage FET based buffer [url="http://www.till.com/articles/GuitarPreamp/index.html"]based on Don Tillman's design found here[/url]. Works great!

I'll try again. This is the brief version. Piezo pickups can sound great on their own. Wider frequency response than typical magnetic pickups. Listen [url="http://hallgeir.no/bass/sound/"]to my sound clips[/url] - the piezo solo clips are in there, read the descriptions.

Bugger. I wrote a nice lengthy response but it got lost.

I recorded the trombone solo for a blues piece of mine using my [url="http://hallgeir.no/bass/benavente/"]Benavente fretless with GK pickup[/url] and the Roland GR-20 guitar-to-MIDI unit. It works fine, great if you play in the upper registers. For bass lines though I'd suggest transposing down an octave or two and playing in the upper register - the tracking is more accurate (timing-wise) there.

Looks very nice. Where did you find it?