Buffer Board Schematic?

I'm considering building the Buffer suggested in Appendix C in the AC BOX Manual (I've built some guitar stomp boxes before, so I know the basics). However, it seems that one component is missing from the schematic. The parts list show C1 at 0.22uF, but it's not listed in the schematic.

I assume that this is the input capacitor, and that it's supposed to go before or after R1, but I'm not sure which.

Any suggestions?

 

I'm pretty shure that it's the input capacitor as well. It's basically just a voltage follower circuit, and all the other capacitors you would want to throw in there seem to be present already..

I would put it before R1.

J.

 

C1 is optional, and I should have left in the paragraph that explained that

If you're using passive pickups, it's best to go directly into R1. With the guitar's volume up all the way (where most guitarists leave it anyway), this creates a situation where the resistance of the pickup becomes the source resistance to ground for the op amp. The coil resistance (not impedance) is around 5-10k, and as it turns out, this is the "sweet spot" for minimum noise with a bipolar op amp.

However, if there is any chance that the guitar might be generating DC offset (e.g., active electronics), then it's a good idea to insert C1 in series with the input jack and R1.

Sorry for the confusion and thanks for the opportunity to clarify this.

-- Craig

 

Thanks!

(Wow! Here I am on a digital guitar amp modelling forum asking questions about analog electronics, and guess who shows up to answer - the "man who wrote the books" on analog guitar electronics - Craig Anderton. I'm impressed!)

 

Well, you can thank NI's Sascha Kubiak, he wrote me and mentioned this thread. Glad to help out

BTW I must say I think Guitar Rig and the Guitar Combos really rock. What you can do with splits and Guitar rig is awesome...a lot easier than soldering, too!