Hi guys

I've ordered one of these: http://www.ebay.com.au/itm/141013304676?ssPageName=STRK:MEWAX:IT&am...

My question is....how (if I can) would I add a volume pot to this?

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Looks like a rod piezo and jack, but no preamp. Looks to me like you have to run it to a preamp or preamp/amp combo to get some gain before using a volume control. Disk piezos are really hot in that they send out a strong signal so you can have a volume pot right off the bat. My understanding is that the signal from a rod piezo is much weaker and has to be boosted.

That being said, lots of people do stuff on this list, and most of the time it works. So someone may have a better idea.

Thanks for your input David....certainly food for thought.

Thanks Wayfinder - will keep all that in mind.

I'm in the very early stages of my CBG building journey having just completed my very first. I would like to experiment with many options before settling down to a set or preferred materials as it were. I'll see how this rod piezo goes and if I'm unhappy with it just put it down to experience.

You can certainly add a passive volume control tho...

Rather than copy paste you one of Mr Ted's famous diagrams and that's it (as is the standard response here to this question) let's talk basics, how a volume control works..

There are two basic ways to use / view a potentiometer..
1 as a voltage divider
2 as a variable resistor

Approach 1.. A voltage divider..
There are three lugs to solder a wire to on your potentiometer..
Imagine some current entering thru the centre lug..
If the pot is turned fully to one end, the current all leaves thru one of the side lugs. If the pot is fully turned the other way the current all leaves thru the other outside lug. If the pot is somewhere between the two extremes then the current is divided between the two outside lugs accordingly.

To make a volume control using this approach we can solder one of the outer lugs to ground, and the other to the hot output from the pickup/pickup selector... And we can connect the centre lug to the hot side of the output jack.
This is the more common approach to a passive volume control.

Approach 2, variable resistor.
Use only two of the lugs, the centre and one of the outer ones. The third lug is unused. This is like a water faucet. We use this approach when there is more than one volume control, like on a Gibson guitar type circuit because otherwise turning one pickup down can turn both of then down as signal is sent to ground.

Great explanation!...as always. Thank you so much. Really appreciate it.

My only add would be:  Since piezo's have a high impedance, you should use a high-value pot... Like 1MOhm, or 500kOhm, and "audio taper"...

There's an article here somewhere on using vol. controls with piezos, and the recommendation was to use a very small capacitor or you roll off the high frequencies with the volume control... I'll go see if I can find it...  I would assume it applies to Rod piezos, but I dunno...

Thanks John - any help is all appreciated!

That's great - thanks again John

Though all the above works, personally, I've found that adjusting my amp makes it easy...  I don't bother with vol/tone knobs unless it's on a coil pickup...  

...and, do you know John, that's crossed my mind too.....

Ok, so the rod piezo/jack assembly finally arrived.
I assumed it was as simple as locate the jack, cut the prize rod into the bridge and away you go. However.....it doesn't appear to be working...have I missed something? Does it need to be grounded perhaps. If so, how would I go about doing that?


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