Grateful Dead Music Forum

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Chat about Equipment Info
 #89242  by Rusty the Scoob
 Thu Nov 11, 2010 8:54 am
My Starfire has a problem - when I hit a good hard bomb it overdrives the internal electronics. This won't do, I can't keep hitting gentle bombs. Also, the twin Bartolini premps eat 9V batteries for breakfast - one per gig if you're like me and can't stand it when they droop below 8.5V or so. So my thought is to power them at 18V for more battery life and headroom.

The trouble is that there's also a buffer/blender (a Rick Turner design/product) that takes a different kind of power - some sort of "Swing Voltage" that requires two 9V batteries with a feed from the + of one 9V, the - of the other, and a feed from the blended +/- between them. I can't think of a way to make both power sources switcheable when the cable is unplugged and not blend them together.

At first I thought of a toggle switch for the 18V, but I don't want to be responsible for remembering to turn it off. Then it hit me - how about a separate TRS jack that can work as a switch if you insert a dummy mono plug, and also as an input for an external 18V power source?

Apologies for the crude diagram - but I think this could work!
External 18V power source idea.JPG
External 18V power source idea.JPG (39.82 KiB) Viewed 414 times
You guys are way better at electronics than I am... what do you think?
 #89243  by playingdead
 Thu Nov 11, 2010 9:15 am
The Voodoo Labs Pedal Power 2 can either provide out you with two 9 volt feeds or one 18 volt feed off AC (they make a special cable for the Q-Tron that runs off two of the normal jacks on there). I would assume you could fabricate a long cord to run the power to your bass from your rack along with the signal cord for the bass.

Not sure about how or why you have to mix off the + - from each battery ... or if just interrupting the ground off one of them using TRS cable would do it. An XLR cable would give you three pins to wire with, though. I assume an XLR cable can carry power since it already does for microphone phantom power use. It would be a whole lot easier to get the batteries out of the equation entirely.

I would think Rick Turner would have some thoughts on it, he's over on TGP a bit.
 #89269  by hogan
 Thu Nov 11, 2010 1:48 pm
Why the 2 active circuits? Me no understand. I don't play bass but to me this seems like putting active emgs and a buffer into a guitar.
If you can afford to pick one system, you should make a signal/power supply breakout box like Alembic. They use a 5pin xlr cable. I've made the cable before. The box would be a couple of filter caps, a flatpack transformer , a voltage regulator for your desired voltage, a fuse, a eic power connector, a 5pin xlr jack and some 1/4" jacks. Bobs your uncle, Fannies your aunt.
 #89297  by Rusty the Scoob
 Thu Nov 11, 2010 5:47 pm
I don't really understand why the Turner buffer requires the voltage it does, I just know it's not compatible with regular 18V. But I'm happy to report that my idea works perfectly! :cool:
 #89303  by zambiland
 Thu Nov 11, 2010 8:04 pm
I'm glad it works out. However, you can get 1/4" jacks with pretty elaborate switching that isn't part of the signal path. Alembic uses one for their 1/4" jacks on the series instruments to switch on the 18 volt onboard power. You want to talk juice suck, those go from 18 volts down to almost tasteless (using my favorite battery checker, obviously) in under 3 hours.

Weird about your Bart preamp, though. I used to get 3 or 4 months of 5 nights a week out of a set of batteries when I had a Bart pre in my Starfire. Plenty of headroom for most of the lifespan, with Dark Star pickups, which have a hefty output.

 #89315  by Rusty the Scoob
 Fri Nov 12, 2010 4:56 am
The way it was wired when I got it, it had two onboard batteries and one of them was helping power the buffer and was solely powering both Barts. I don't run my batteries down to zero, for me most (but not all) preamps lose their fatness when the batteries droop to 8V or so.

My headroom issue might also be the Dark Stars and Barts overdriving the DTAR Eclipse... I think it's more meant for acoustic guitar pickups and/or piezos...

Interesting about the multiple-switching jacks.... I haven't seen those.