volume and tone pots

[cjtrucker]

i have built several cbg every one better than the last but have not been able to find volume or tone pots that match up with the piezo transducers i use for p.u.

[Ottie(Sky Dog)Noble]

Forget the tone pot, and use a 500k for the vol it'll work out great. Or at least it does for me.

[cjtrucker]

thanks ill get one today and let you know how it worked

[David L.]

I found this tucked away with a google search
"The only way to get a passive tone control working with a piezo pickup is to have a resistor in series with the pickup before the signal reaches the tone control. The larger the resistor, the more effective the tone control will be. Unfortunately too large a resistor will also lose output, so a compromise value would be needed. This is the main reason that acoustic preamps are used in the guitar, so that the piezo pickup signal goes straight to the preamp input and the pickup is buffered by that, then the tone controls come after (or within a later stage of) the preamp. Then in that case, they will work as expected, usually with boost and cut of the various ranges."

It was from here
http://charliehall.proboards.com/index.cgi?board=saved&action=p...

As I have never found a passive tone pot works with a piezo using the same method as for a magnetic pickup I'll have to give it a go.

Has anybody else tried this?

[cjtrucker]

thanks for the help, i have very little electronics experience but would like to add volume control to my next build, the problem i have with the cbg;s i have already made is feedback and i'm only guessing but it seems that a volume control could help with this, am i right or am i on the wrong trak?

Naz Nomad said:

You haven't really described what your initial problem was, so I'll throw this into the mix.

I've heard many stories from reputable (?) folks about the output impedance of piezos being too high to work well with passive controls and the need to buffer/pre-amp/blah-blah-blah/bullshit/etc.

Now, I'm not 'totally' disagreeing with those people because, quite possibly, they may be right. However, I have lost count of the times that I've heard people (myself included) get amazing results without buffering. Don't believe me? Give Dave Wendler a call, he's probably been doing this even longer than I have.

Anyhow, despite what I say here, ''your mileage may almost certainly vary'' with passive tone controls on piezo transducers.

Naz