Guitar Pre Revisions?

[Nigel Goodwin]

Originally posted by cheeseburgerjoe
[B]I will try shorting the bottom 100k resistors. Should 200k be sufficient?

It's better than having 100K's in the bottom of the pots, but 200K is probably more loading than the pickups are designed for.

I finished the schematic for the brain module I've prototyped *I know, I know, schematic THEN prototype, lol* so here's a copy of that.
I realize that with the current design the brain is not biased to 1/2v *I added the output bypassing caps to the on board preamp, and have made no changes to the brain yet. I WAS going to change schematic for 15v dual supply *guitar pre will be running single supply still.* But instead, I've decided to re-design the brain using ad5206 *6ch digital pot* instead of 4066s. The problem here being that the 5206 is 5v. Still pondering the best way to make this work. Here's a schematic for the brain, the bypass module is for testing purposes only. I have ommited the BS2 from schematic, nothing complicated here. The 12pin feeds 5v to bs2, the other 9 wires are pin to pin connection. I will be making ANOTHER schematic for the bs2 board in the next couple days.

It's all getting very complicated

BTW, instead of using opamp buffers from the pickups, have you considered simple FET source followers?.

[cheeseburgerjoe]

I just revised my schematic. I'm trying the KISS method. Any thoughts Nigel? I'm also wondering what I should do with my power supply? I'm probably going to use the one from my Kawai K3m. It's +12v- +5v and I don't plan on using the -12v right now. Is it ok to leave the output unconnected?

[Nigel Goodwin]

Originally posted by cheeseburgerjoe
I just revised my schematic. I'm trying the KISS method. Any thoughts Nigel?

Looking better, but you are making a substantial loss through the input attenuator.

I'm also wondering what I should do with my power supply? I'm probably going to use the one from my Kawai K3m. It's +12v- +5v and I don't plan on using the -12v right now. Is it ok to leave the output unconnected?

I would expect using just the 12V positive should be fine.

[cheeseburgerjoe]

I guess I'm still doing something wrong. I built the new version and I get no output. When I turn the power off, it works for a second. I'm thinking I need to move the summing resistors after caps. I've only had a little while to test for mistakes.
Should I be using op amps to buffer the output or should I be ok without them. Also I'm thinking about making the pickup switch output to one wire. Simple voltage divider setup to make the on - on - on switch output gnd - 6v - 12v. Is there an easy way to decode this on the other end?