My Bass Preamp

[ubersam]

Hey all.. been away from here a long while... anyway, I clobbered together a bass preamp based loosely on the Fender Bassman. It is essentially two Fetzers with a tonestack/vol control in the middle. I added another volume control at the end, effectively making the middle volume control the gain control. I didn't intend to use this as a pedal so bypass switching wasn't included, but there is an on/off switch. Power switching is done by connecting/disconnecting the ground from the power supply. I even included Jack Orman's LED trick. Turning the unit on is nice and quiet, no pop. But when I power off, that is when I get the loud pop. Anyone know the right way to correct this? I have a couple of ideas for eliminating that pop, but I haven't tried them yet to see if it would work. The first idea is to ground the output when switching the power off. The other idea is to put a resistor and cap in series across the switch terminals. Here is a link to the schem: http://i112.photobucket.com/albums/n188/ubersam/schematics/BassPreamp.jpg

[PRR]

I do not understand the complicated power switching. Is it on good authority? Is it copied correctly?

IMHO: Just hard-wire grounds, break Vb, wire LED+R from Vb to ground.

Yes, such circuits do pop. Reducing C11 C13 to 1/10th the present value may reduce the violence a bit (without shaving bass). Sometimes a short on the output "is the best fix". It's done on some very high-class gear.

[ubersam]

Hey Paul, Thanks for the input. I adapted the idea for the power switching from how I've done it with pedals using the instrument input jack and the sleeve of the 1/4" plug as the "switch" that connects/disconnects the ground. Now that I think about it, breaking the ground to power off may not have been the best idea for this project. Also, I'm not sure now why I chose to use a DPDT when an SPST would have worked just fine. I'll try tying the output to ground through the switch in the off position first and see if that fixes the pop.