Comment

Comment by Bill Harbour on May 11, 2011 at 4:15am

Here's a shot of the notch with the 100K dual pot a minimum.  Almost 19dB reduction at 4KHz.

Comment by Bill Harbour on May 11, 2011 at 4:13am

Here's an updated schematic of the notch filter.  I removed the 500K pot from the input and placed it after the J2 amp stage.  I also changed a few resistor values around to yield better performance. 

Comment by Bill Harbour on May 11, 2011 at 3:50am

I quickly assembled the buffer onto the jack last night...overall it did help tone down some of the harshness, but not completely.  Especially when the volume pot was turned full on.  I added the buffer after the volume pot and later realized that there's still a mismatched impedance between the piezo and the volume pot.  I'll build a buffered, preamp with the 500K volume pot after the preamp stage.

Comment by Bill Harbour on May 11, 2011 at 3:44am

MichaelS...you using Radio Shack piezo elements?  Where are you placing them and are you using a preamp?

Comment by MichaelS Country Boy Guitars on May 11, 2011 at 12:24am

Hi guys, I put piezo's in all my cbg's and they work great.

Comment by Gustavo sanchez on May 10, 2011 at 10:05am

I will dig in my old notes for I filter I used a few times with success. Is called a "buttefly" filter system, with AMP included for weak signals, specially made for piezo sensors. Based on the LM393(?) and few resistors & capacitors .... Hope I can find it ...

Comment by Gustavo sanchez on May 10, 2011 at 9:59am

I

Comment by Gustavo sanchez on May 10, 2011 at 9:59am

I

Comment by Gustavo sanchez on May 10, 2011 at 9:58am

Bill : You went all the way my friend with this design !!! .... I had to admit tha is way much more complicated than the others, but I bet also that is much more reliable and as you mentioned, no need for inductor .... I recall working on School with inductor projects and all of the drove me nuts... are very hard to adjust I agree with you, but on the other hand, the resulting noise reduction is beautiful .....

Comment by Bill Harbour on May 10, 2011 at 9:49am

One additional note...the notch is variable and can be moved from 400Hz to 4KHz.  That way you can adjust the control and find the exact offending frequency.

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